University of the Witwatersrand, Johannesburg
SCHONLAND RESEARCH CENTRE FOR
NUCLEAR SCIENCES
Annual Report
1998-9
Diamond Bending Device (see page 41)
Introduction ..........................................................................................................................3
Applied and Environmental Physics Research Group .........................................................4
Ion Implantation and Surface Studies Research Programme .............................................19
Nuclear Physics Programme ..............................................................................................28
Wits-Northern Accelerator Research Centre ...................................................................32
Health Physics Service ......................................................................................................69
2
Introduction
This Report covers the first full year (1998) of the implementation of the new Schonland proposals,
plus part of 1999, being based on the reports prepared by the various Groups for their Annual General
Meetings at different times in 1999. In accordance with the Physics Department's plan, the Schonland
Research Centre for Nuclear Sciences is now in effect a federation of four Research Programmes,
each with its own Group Leader, sharing a common support infrastructure. In addition the
University's Health Physics Service has its home at the Schonland. Some of the Groups are
subdivided internally along the lines of individual research interests, as will become apparent in this
Report.
Matters of common interest are overseen by a Schonland Co-ordinating Committee with a rotating
(2-year) chairmanship, chosen from the Group Leaders. The Chairman for most of the period under
review was Prof. Vladimir Hnizdo, but since his resignation in the middle of 1999 to take up a post in
America, Prof. Trevor Derry has taken over the job.
The four recognized Research Entities are:
- Applied and Environmental Physics Research Programme (Prof. J.I.W. Watterson);
- Ion Implantation and Surface Studies Research Programme (Prof. T.E. Derry);
- Nuclear Physics Research Programme (Prof. V. Hnizdo then Dr. J.M. Carter);
- Wits Northern Accelerator Centre (Dr. S.H. Connell).
To these must be added the Health Physics Service (Dr. T.L. Nam).
The current membership of the Schonland Co-ordinating Committee is:
Prof. T.E. Derry (chair), Dr. S.H. Connell (deputy chair), Prof. J.I.W. Watterson, Dr. J.M. Carter, Mr.
A.H. Andeweg (Technical rep.), Mr. D.B. Rebuli (Postgraduate rep.), Prof. B.J. Cole (Head of
Physics Dept.) and Prof. W.U. Reimold (Geology Dept.); other representatives attend meetings from
time to time.
The Schonland Research Centre's mission is to pursue a vigorous programme of both pure and
applied nuclear research for the African context, including overseas collaborations where appropriate,
integrated with the training of our higher degree students.
The University's recognition of separate Research Entities under the Schonland umbrella has been
very successful. Attention and effort has now been freed for the business of research and teaching,
and several major projects have blossomed, as detailed in this Report. Notable has been the
implementation under International Atomic Energy Agency auspices of an annual five-month
Radiation Protection Course serving the whole of Africa, which necessitated major structural changes
to the Schonland buildings to accommodate some 20 students plus donated equipment.
Trevor Derry.
February 2000
3
Applied and Environmental Physics Research Group
August 1999
J.I.W. Watterson
and
B. Th. Verhagen
4
1. Introduction
The philosophy of this group is to carry out intrinsically interesting research in physics in an
academic way and apply it to areas that are of interest in and practical importance to a developing
country like South Africa. It is a fact that much of the research, particularly in physics, in most
developing countries is not of direct relevance to that country. It does contribute to the development
of humankind and it is certainly of cultural importance, but it does not contribute to the economic,
environmental or social well-being of that particular country.
Jeffrey Sachs, Professor of International Trade at Harvard and Director for the Centre of International
Development has made this point particularly well in a recent article in the Economist. He points out
that the vast majority of scientific research is undertaken in areas that are mostly only of direct
relevance to developed economies. He presents a chart which shows the overwhelming dominance of
the rich countries in publications (90% of the total) and patents (95% of the total). He also points out
that rich countries even benefit from the scientific talent of the poor countries and that many of the
scientific and technological breakthroughs are made by poor-country scientists working on richcountry problems in rich-country laboratories. This could be further extended by observing that t even
research in the laboratories and universities of the developing countries uses scarce local human
resources and equipment to contribute to the solution of problems mainly of relevance to rich country
science and hence to the economies of the richer nations.
Two South African examples that spring to mind are those of computed tomography discovered by
Cormack in South Africa in the 1960’s and radical heart surgery associated with the name of Chris
Barnard. In spite of the fact that these originated in this country, today CT scanners are all
manufactured in the United States or Europe and artificial heart valves are manufactured in the United
States and sold throughout the world. The economic benefits of these world class advances have been
negligible in the country of their origin.
The Applied Physics Research Group pursues lines of research established by us in the Schonland
Centre over many years, applying the techniques of Physics to the understanding of problems of
economic and social importance in the context of Africa. This programme has three main themes: the
application of isotope measurements in the understanding of water systems, the application of
nuclear-based methods to mining and the understanding and measurement of radiation in the
environment. All of these fields include elements of pure science and academic research as well as the
development of direct economic and social benefits.
The application of isotope measurements in the understanding of geohydrology has been pursued at
the Schonland, since its founding as the Nuclear Physics Research Unit in 1960, in the Environmental
Isotope Research Group. Under the leadership of Prof B. Th Verhagen, the Environmental Isotopes
Laboratory has been established as probably the foremost laboratory in Africa for the measurement of
light isotopes in this field.
The development of nuclear techniques in mining had its origin in the National Institute for
Metallurgy’s Activation Analysis Research Group, which was later broadened to include the
development of techniques for on-line measurement.
5
It is important to realise that these activities, together with air pollution studies and many programmes
on diamond physics, and geology always were the core research programme of the Schonland Centre.
Other activities such as the neutrino collaboration with Frederick Reines of Case Western University
in the 1970’s and various experiments on Nuclear Physics were peripheral.
There are thus three main programmes in the Group, the Environmental Isotope Programme, the
Applied Nuclear Physics Programme and the Programme on Radiation in the Environment.
2. Environmental Isotopes Programme
2.1.
Historical
The Group had its beginnings in the late 50's as the tritium laboratory, the initiative in the Department
of Physics actually pre-dating the establishment of the Nuclear Physics Research Unit, which was to
be renamed the Schonland Research Centre (SRC) in the mid-eighties.
The initial aim was the development of methods to enrich environmental tritium. The practical
applications of tritium to hydrological problems were made in the late 60's. In the early seventies, the
requirement of studying deep ground water with high residence times in the Kalahari prompted the
development of radiocarbon analysis. A Water Research Commission contract to study ground water
in the northern Cape and Sishen mine allowed for the expansion to stable isotope analysis which
added mass spectrometry to the facility, re-named the Environmental Isotope Laboratory, in the midseventies.
Numerous studies, mainly of ground water systems but also of other environmental concerns
followed, using the largely home-built low level counting facilities. During this period, the
Environmental Isotope Group (EIG) became internationally acknowledged, generating many
cooperative studies and research contracts. These were conducted with this and other universities,
local and international research bodies, government agencies, and the private sector. The Group
Leader spent several extended periods abroad being invited to participate in projects in this context.
By the mid-nineties, the Group became more actively engaged with the International Atomic Energy
Agency (IAEA) in cooperative research programmes (CRP's) and a Regional Model Project for
northern Africa, involving seven countries. The Group rendered expert services to this project in the
course of which a similar endeavour for southern and eastern Africa was proposed. This new model
project, which had its inception on 1 January 1999, is centered on the EIG as a regional facility
responsible for training, scientific input and analytical services. To facilitate the latter, the EIG stands
to receive an infusion of state of the art analytical equipment for a total of some R 2 million from the
IAEA.
With the re-structuring of the SRC in 1997, the EIG became part of the Applied and Environmental
Physics Group (AEPG).
The EIG is at present largely self-supporting and is led by Prof B Th Verhagen, retired in 1997, at
present Honorary Research Fellow. Active steps are being taken towards leadership succession for the
EIG.
6
2.2.
Some past achievements
Research at the EIG has revolutionised the hydrology of the Kalahari and other arid and semi-arid
environments. This work demonstrated for the time that ground water renewal is an ongoing process
in such environments and that resources are not "fossil", or the remnants of earlier "pluvial" periods
as believed previously.
The most rewarding of these studies has been producing a conceptual model for the aquifer feeding
the northern wellfield of Jwaneng diamond mine in SE Botswana. This has led to an understanding of
previously puzzling aspects of the well field's performance; estimates of recharge, later confirmed by
water balance studies and information on the potential vulnerability of the system to pollution with
changing land use.
The Group has been invited by governments and the private sector to participate in numerous major
ground water development projects with considerable success in contributing to conceptual and
numerical modelling and thus to the overall resource assessment. This framework of operation could
be recommended to the IAEA in their endeavours to propagate the technique especially in developing
states.
The final report on a Water Research Commission project and subsequent publication (Verhagen et
al. 1999) showed for the time that estimates of ground water recharge in several studies based on
isotope "snapshot" data could be corroborated by independent methods which required sometimes
many years of observations.
The Group's work on ground water pollution using a wide spectrum of environmental isotopic tracers
has been ground-breaking. In various studies using stable isotopes of water and of nitrogen, sources
of pollution could unequivocally be established. The Group discovered the distinct isotopic signal on
Gauteng mains water as a means of tracing such water in the environment; discovered artificial
tritium in landfill leachate as a means of tracing such leachate in the environment; produced the
concept of incipient pollution - at concentrations which may not yet be chemically evident but can be
identified by their isotopic association.
Using stable isotopes and tritium the Group developed an approach to urban hydrology almost unique
to South Africa: using the numerous private boreholes as sampling points for pin-pointing leakages.
In the process, interesting small-scale features of ground water recharge were discovered.
The Group contributed to a number of studies by other Departments within this university, notably
Geology, Archaeology and Botany as well as at other universities. The Group leader made a major
contribution to a wide ranging set of isotope hydrology investigations in the arid zone undertaken by
the Federal Geoscience Institute, Hanover, FRG.
2.3.
Aims and nature of the EIG
The aims of the EIG are the application of both radioactive and stable isotopes of mainly the light
elements (H,C,N,O,S) to the study of processes in the environment. The fields of mostly
interdisciplinary research have been hydrology, archaeology, geology, and the life sciences.
The staff of the Group at present consists of the Leader, Prof B Th Verhagen, Mr M J Butler,
Research Officer, and two laboratory technicians, Messrs O H T Malinga and B Kumalo.
7
Its analytical facilities consist of the following:
* two isotope ratio mass spectrometers (IRMS), one purchased in 1975, the second of about the same
vintage, recently donated by the CSIRO in Australia. These are amongst the very few of these
instruments world-wide still being kept operational
* two state of the art low level liquid scintillation spectrometers, the purchased from EIG funds with
supplementation by the University three years ago; the second was commissioned two weeks ago and
is part of the upgrading package financed by the IAEA under the regional model project. The homebuilt gas counting system was scrapped recently.
* various vacuum lines for sample preparation and handling and general laboratory facilities
Tenders have recently been called by the IAEA for a state of the art mass spectrometer, which is expected to
be delivered and installed within the next few months.
2.4.
Summary of activities during 1998-99
2.4.1. Activities: 1998
B Th Verhagen travels on expert missions to Uganda and Ethiopia to assist counterparts in IAEA projects to
complete their final reports (January). Further investigation with Dr C J Barnes of Australia of the Lake
Beseka problem in Ethiopia (January/February)
B Th Verhagen presents invited paper at ICARID international conference in Mumbai, India (February).
The EIG hosts a planning meeting on the project Sustainable Water Resources in Johannesburg attended by
representatives of seven southern and eastern African countries. The EIG obtains unanimous support for being
appointed Regional Centre for this project (March).
B Th Verhagen presents paper at the International Conference on the Role of a National Geological Survey in
Sustainable Development, Gaborone, Botswana (May)
B Th Verhagen presents paper at Geocongress, Pretoria (July)
B Th Verhagen initiates Taaibosch Fault project, South Africa's contribution to the regional model
project Sustainable Groundwater Resources (October)
M J Butler attends a research ordination meeting in Sfax, Tunisia on the CRP on Anthropogenic
Influences on Groundwater Renewal and presents the Wits progress report (November).
B Th Verhagen travels to Madagascar on an expert mission under the project Sustainable Water
Resources (November)
O H T Malinga and J A Geyer of the EIG attend a training course on laboratory techniques in Vienna
(November)
Scientific visit to EIG by Messrs Dribidu and J Karundu, Entebbe, Uganda (November)
Delivery of second-hand mass spectrometer donated by CSIRO, Australia (December)
8
2.4.2. Activities 1999
B Th Verhagen attends RCM on the project Sustainable Water Resources and presents reports on the
South African and Madagascar projects (February)
B Th Verhagen travels to Namibia on a joint mission with Dr K Froehlich of the IAEA to investigate
the feasibility of that country's proposed project in the regional Sustainable Water Resources
programme (April)
B Th Verhagen and M J Butler attend international Isotope Hydrology Symposium in Vienna and
present paper and poster (May)
The IAEA accepts an EIG project proposal: Long-term isotope data series and the hydrological model
of Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological
systems to long term exploitation (June)
B Th Verhagen presents a paper to the International Conference of the Geological Society of Africa in
Cape Town (July)
Delivery and commissioning of liquid scintillation spectrometer purchased by the IAEA under the
regional model project (July/August).
sampling by M J Butler and B Th Verhagen of all Jwaneng production boreholes (July/August). This
project is a continuation of a long-term investigation of the Jwaneng well field aquifer which shed
much light on the geohydrology of the Kalahari.
B Th Verhagen visits Namibia to jointly initiate that country's programme under model project
Sustainable Water Resources (August)
Following modifications, donated second mass spectrometer brought into operation (August)
During the past few years, considerable contributions have been made to problems of ground water
pollution. Numerous smaller projects were completed with the private sector in 1998/99.
A tritium - oxygen-18 diagram of ground water and surface water from the Wurno irrigation area,
NW Nigeria. The various components (upwelling deep ground water, irrigation and seasonal floods)
of recharge to shallow ground water could be separated in order to predict vulnerability to ground
water pollution.
2.5.
Some Ongoing Projects
Isotope studies of thick unsaturated zones in semi-arid areas of southern Africa in the IAEA CRP on
Isotope-based assessment of groundwater renewal and related anthropogenic effects in water scarce
areas. Third project year.
IAEA projects RAF/8/022 in Nigeria and UG/8/002 in Uganda nearing completion. Assist Uganda in
preparing final report.
9
Work has started on the project: Long-term isotope data series and the hydrological model of
Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological
systems to long term exploitation.
Little Karoo fractured aquifer study. This is a joint study with the Department of Water Affairs, under
contract to the Water Research Commission and partially under an IAEA technical operation contract.
Various smaller ad hoc projects, mainly on local water resource assessment and pollution issues with
the private sector.
Ground water resources assessment in the Taaibosch fault zone, N Province. This is South Africa's
component in the IAEA RAF/8/029 regional model project.
A recently initiated investigation of ground water resources in the south-east artesian basin, Namibia
under RAF/8/029 IAEA regional model project
Five other projects, in Uganda, Tanzania, Kenya, Zimbabwe and Madagascar under RAF/8/029 are to
be initiated within the immediate future.
The EIG has for some 15 years contributed tritium, deuterium and oxygen-18 data on monthly rain
water samples collected from four southern African stations under the IAEA/WMO Global Network
for Isotopes in Precipitation (GNIP) as a national service free of charge.
2.6.
Students and Teaching
I Mahomed, M Sc. Registration to be revised
J Kotze, PhD Joint supervision with the University of the Free State
M J Butler, MSc (1998) PhD to be registered when project proposal finalised.
The EIG has assisted in several Geology Honours projects
B Th Verhagen assists in teaching geohydrology to Geology Honours, part-time MSc and GDE
classes
Future of the EIG
Activities in the immediate future of the EIG are likely to be dominated by the regional model project,
which will involve training, scientific support and isotopic analyses in pursuance of the project. This
endeavour is establishing research partnerships with six southern and eastern African states and
strengthens operation with the Department of Water Affairs in South Africa.
Once the present re-organisation and rationalisation of the Environmental Isotope Laboratory is
completed, active endeavours will be made to attract more post-graduate students.
With the passing of the new water act in South Africa the State has to assume greater responsibilities
in the management of water resources. Isotope hydrology has been identified as an important tool in
providing basic data on e.g. ground water systems and the EIG is seen as an important national asset.
Following the drawing up of a Country Programme Framework (CPF) for IAEA support under its
Technical Cooperation Programme, sustainable water resources and isotope hydrology as a key
initiative in support of this goal is high on the agenda for research proposals recently called for by the
10
NRF. Various proposals will be submitted by the EIG, including developing approaches to fractured
rock aquifer studies, isotopic studies of the origins of nitrates; the role of radon as a ground water
tracer; refining recharge estimates using environmental isotopes; national ground water vulnerability
mapping - an extension of an initiative recently initiated with the Department of Water Affairs;
ground water pollution studies using a variety of isotopes including tritium in landfill leachate;
extending the national data base on isotopes in precipitation, surface water and ground water.
The EIG, with its modern low-level counting capacity, two operational isotope ratio mass
spectrometers and a third state of the art instrument expected shortly, along with the Hugh Alsopp
isotope laboratory and facilities in the Department of Geology, will place the University in a very
favourable position to compete for housing the proposed National Isotope Facility. This may in time
be further complemented by the development of accelerator mass spectrometry at the Schonland
Research Centre.
3. Applied Nuclear Physics Programme
This programme concentrates on the detailed understanding of nuclear interactions with a view to
their application to practical problems. In view of the over-all philosophy of the group and its aims
these have primarily been in the mining industry. The most active project at present is that of
Resonance Neutron Radiography.
3.1. Resonance Neutron Radiography
This project is a collaboration between the University, the Mineral Processing Division of De Beers,
the Department of Nuclear Engineering at MIT, the South African Atomic Energy Corporation and
Brookhaven National Laboratory. There are many different facets to it. It is based on the development
of element sensitive neutron radiography based on resonances in the neutron cross-section plotted as a
function of neutron energy.
The imaging process depends on the ration between the macroscopic cross-sections for the feature of
interest and for the material in which the feature occurs.
There are two major regions of interest. One is at the oxygen “hole” around 2.3 MeV and the other is
in the region of the resonance between 7.4 and 8.3 MeV. It turns out that the physics of neutron
production favours the high energy resonance using the reaction 2H(d,n)3He with 5 MeV deuterons
produced by an accelerator. This could be a cyclotron or an RFQ accelerator.
This project has gone through a number of different phases. In the initial phase (started effectively in
1993) use was made of the accelerators at the National Accelerator Centre, the Schonland Centre and
the AEC. In 1994 the Group Leader spent a short sabbatical at MIT (sponsored by De Beers). After
his return, a 2MeV RFQ accelerator was installed in the Neutron Source Laboratory at the Schonland
as part of this ‘proof of principle” phase. De Beers contributed some R500 000 to the University in
full support of the temporary acquisition of this accelerator.
The Group has continued its active involvement through a collaboration with MIT on an intermittent
gas target, and research on the physics of the imaging process. This research is still continuing.
11
This programme involves three PhD students, two full time and one part-time (R. Ambrosi, H.
Rahmanian and J. Guzek). The part time student has successfully submitted his thesis and should
graduate later this year. The other two students should submit next year.
The work by Richard Ambrosi is particularly interesting, involving the use of an amorphous silicon
imaging panel of a type that is being developed for medical x-ray diagnostic applications. This panel
has been characterised by the candidate and it should prove extremely useful in the future. This puts
the University at the forefront of research into imaging with the purchase of this panel. Some
R400 000 was raised from De Beers for this purchase.
The thesis of J. Guzek has concentrated on the investigation of the physics of neutron production and
the optimisation of this aspect of the project. In addition he has been concerned with the integration of
the techniques into a practical system.
This work has lead to many research papers in international journals or reviewed conference
proceedings, and a number of presentations at local and international conferences including five
invited papers.
It has also lead to a number of patents held jointly with De Beers and owned by De Beers. Through
this programme this group has achieved recognition as one of the world leaders in fast neutron
radiography.
The programme has brought considerable financial resource into the University. This includes the
provision of an accelerator for a year and running expenses as well as student support. This year we
had about R330 00 of support from the THRIP programme and this money will be used to purchase a
new camera for imaging purposes. It is estimated that the total value of this support over the last six
years is in the region of R3m.
3.2.
On-line Analysis and Sorting
This programme has supported a number of projects aimed at investigating the fundamental nuclear
interactions and detection methods that can be used for on-line analysis and sorting. These include
inelastic scattering reactions with carbon for the analysis of the energy content of coal and the gold
content of gold ore. This last reaction: 197Au(n,n’)197mAu was the subject of research leading to the
award of an MSc degree to T. Magagula in 1998. He investigated this reaction using neutrons
produced through 7Li(p,n)7Be on the Schonland tandem accelerator with a lithium target. He
investigated how the neutron spectrum from this reaction could be used to excite the gold without
exciting reactions with silicon and aluminium and so achieve the optimum limit of detection for gold
in rock. The results were presented at the ECART Conference in the Netherlands in 1997.
With the new developments in accelerator technology being pioneered on the previous project, this
idea could become practically feasible and a low energy high current accelerator with a gas target
should be investigated. The correct energy could be found by varying the angle of emission of the
neutrons. An idea that is being developed is to do this as a project with De Beers with support from
the DACST Innovation Fund.
Projects on on-line analysis of coal and other systems will also be pursued under this heading.
Another idea that is being developed is that of applying a variant of the resonance neutron
radiography technique that has been developed to the determination of explosives and other
12
contraband such as drugs. This depends on the use of the fact that the energy of the neutrons varies
with the angle of emission. Therefore images of the different elements, nitrogen, carbon and oxygen
could be obtained as the specimen moves around the source. Once again this is being pursued in a
collaboration with DeBeers.
4. Programme on Radiation in the Environment
The importance of the environmental effects of radiation is increasing. This applies to the products
and results of mining and of power generation as well as the natural background. For a number of
years the group has been involved in the use of gamma-ray spectroscopy to measure radioactivity
(principally from radium, the daughter of uranium) in mining products; mainly in zircons from beach
sands.
As a result of this work and new analytical ideas that were developed, the Group was commissioned
to design and build a gamma-spectroscopy system to measure the amounts of uranium and thorium in
these products. This system was delivered to Richard’s Bay Minerals in 1997 and the money raised in
this way has been used as a source of funding for the group’s research.
In addition the International Atomic Energy Agency sponsored programme on post-graduate
education in Radiation Protection is associated with the Group. In this endeavour there is a close
collaboration with the Health Physics Service of the University under Dr T. L. Nam and with the
South African Council for Nuclear Safety. The Head of the Group is also the Director of the Centre
for Post-Graduate Education in Radiation Protection. This Centre has been equipped with about
R1.5m worth of equipment over the past few years by.
There are a number of post-graduate programmes associated with this initiative.
4.1.
Projects on Radon in the Environment
A PhD candidate Alex Tsela has submitted a thesis on the measurement and evaluation of the
emanation coefficient of radon from zircons. In this project an original way was developed for
measuring the radon emitted from very small samples of well characterised mineral grains. This work
has lead to a greater understanding of the emanation process in zircons and to the identification of
anomalies in this behaviour. This work is being carried out in collaboration with Anders Damkjaer of
the Risø Research Institute in Denmark and for some time it was part of the focus of a collaboration
with the University of Swaziland..
A second PhD programme has been started on radon with David Maina from the Institute for Nuclear
Research at the University of Nairobi. He spends some four months each year with the Group. His
project is concerned with the health effects of smoke from cooking fires in rural dwellings combined
with radon in the air. There is recognised epidemiological evidence that people who smoke cigarettes
and are exposed to radon have significantly higher incidences of lung cancer. The objective of this
project is to investigate whether there is a similar effect from indoor cooking fires in rural dwellings
in Kenya and South Africa.
Many people in Africa live in dwellings with earth floors. The radon emission is therefore expected to
be higher relative to dwellings with concrete slab floors. In addition if people sleep on the floor or
close to it, thoron might be an issue. Some areas where there are beach sands for example have
13
regions where the heavy minerals are concentrated. These regions could have high concentrations of
radon, and thoron close to the ground. This project is very interesting and could be of great
importance to the respiratory health of rural communities.
An allied project is being undertaken together with the Environmental Isotopes Laboratory in order to
measure radon in ground water using the technique of liquid scintillation counting.
4.2.
Gamma-ray Spectroscopy for Environmental Samples
The Schonland Centre should be a centre of excellence for the measurement of radiation. A sensitive
method of gamma-ray spectroscopy was developed in the Group that can be used to monitor radium
daughters (214Pb and 214Bi in the uranium chain) and 208Tl in the thorium chain. This method makes
use of Marinelli beakers and a 5” x 5” NaI(Tl) detector. The detector is stabilised using a method
developed by Hugo Andeweg at the Schonland and works well giving very accurate results.
The method has been used over a number of years to monitor the uranium and thorium in mineral
products for export (mainly zircon). As was mentioned above, a semi-commercial instrument based
on this principle was also supplied to Richard’s Bay Minerals. At present the software for this
instrument is being revised.
This technique is being used for the measurement of radium in effluent from slimes dams, in an
honours project with the department of Geology. This research is being inhibited by the need for the
stabiliser on this instrument in the same way as the one supplied to RBM.
4.3.
Post-graduate Centre for Radiation Protection
The new Centre for Post-Graduate Education in Radiation Protection has been developed at the
Schonland Centre in association with the AEPRG and the University’s Health Physics Service as well
as the Council for Nuclear Safety.
The equipment for this Centre, worth about R1.5m, was provided by the IAEA. The course is being
given at present to 19 students from all over Africa (including three from South Africa). The fees for
the overseas students are being paid by the Centre in a complicated arrangement with the IAEA.
Some 12 of the students have registered for the Post-Graduate Diploma in the Sciences.
This Centre will form the focus for post-graduate research in the field of environmental radiation. The
students who successfully complete the diploma can proceed to an M.Sc by examination and research
report. It is expected that a great deal of this research will be carried out in association with the
AEPRG as well as with the Health Physics Service and the CNS.
So far one application has been received from a student who wishes to undertake an MSc by research
as part of this programme and there have been a number of other enquiries. With the decision to
proceed with the initial stages of evaluation of the Pebble Bed Power Reactor concept, there will be
an increasing demand for trained personnel in this field.
14
Publications 1998-1999
B TH VERHAGEN, Environmental Isotope Hydrology, Hydrogeology of the Main Karoo Basin:
Current Knowledge and Future Research Needs. Water Research Commission, Pretoria (1998).
NL INGRAHAM, A E CALDWELL and B TH VERHAGEN Isotope tracers in catchment
hydrology. Chapter in book: Arid zone catchments. Elsevier Science Publishers, Amsterdam, (1998)
839 pp.
BTH VERHAGEN, MJ BUTLER, Environmental isotope studies of urban and waste disposal impact
on groundwater resources in South Africa, In: Isotope Techniques in the study of Environmental
Change. IAEA, Vienna, (1998) 411 - 422.
BTH VERHAGEN, Isotope Hydrology: applications to mining, urban, and pollution problems in
southern Africa., Procs ICARID International Conference, NAARI, Mumbai, 4 - 7 February 1998,
307 - 324.
BTH VERHAGEN, Isotope Hydrology: a success story in the application of nuclear techniques to
environmental problems, Nuclear Technology Conference, Mmabatho, October 1998.
A FOURIE, BTH VERHAGEN, M LEVIN, HD ROBINSON, Tritium as an indicator of
contamination from landfill leachate,Wastecon '98 Conference, Kempton Park, October 1998.
BTH VERHAGEN, M LEVIN, AB FOURIE, High level tritium in leachate from landfill sites in the
Republic of South Africa with emphasis on its distribution and value as an environmental
tracer,Water Institute of South Africa Conference, WISA'98, Cape Town, May 1998, 10pp.
BTH VERHAGEN, Environmental isotope hydrology: past, present and future impacts on ground
water studies in mining, the urban environment and understanding hydrochemistry, Procs
Geocongress '98, Geological Society of South Africa, (1998) 285 - 288.
BTH VERHAGEN, Arid Zone Isotope Hydrology - Cooperation with the Geological Survey,
Botswana, International Conference on the Role of a National Geological Survey in Sustainable
Development, Lobatse (1998) p37.
BTH VERHAGEN, Case studies on isotope hydrology in the Kalahari,UNESCO/IHP Regional
Workshop: Water Resources of the Kalahari Desert, Lobatse, Botswana, 3 - 5 November 1998.
MJ BUTLER, BTH VERHAGEN,Isotope studies of thick unsaturated zones in semi-arid areas of
southern Africa,Progress Report on: International Atomic Energy Agency Research Contract
Number: 335.F3.30.08 to Research Coordination Meeting, Sfax,Tunisia, 9 - 13. 12. (1998) 21pp.
SRCNS 98/08.
BTH VERHAGEN,Investigation of leakages from the Aonob Dam, Namibia. ,Report on project
RAF/08/026 mission (15 - 19 December 1997) to the International Atomic Agency (1998) 5pp.
SRCNS 98/09.
15
BTH VERHAGEN, Isotopes for groundwater development, Uganda ,End of Mission Report to the
International Atomic Energy Agency. Project: UGA/8/002 - 01, 10 - 18 January 1998, SRCNS 98/10,
7pp.
BTH VERHAGEN, Isotopes for groundwater development, Ethiopia,End of Mission Report to the
International Atomic Energy Agency, Project: RAF/8/022 15 01, 19 - 28 Jauary 1998, SRCNS 98/11,
8pp.
BTH VERHAGEN (1999) Environmental Isotope Hydrology. Chapter in book: Hydrogeology of the
Main Karoo Basin: Current Knowledge and Future Research Needs. Water Research Commission,
Pretoria. In press.
B TH VERHAGEN, M LEVIN and A FOURIE (1998) High level tritium in leachate from landfill
sites in the Republic of South Africa with emphasis on its distribution and value as an environmental
tracer. WISA ‘98, Water Institute of Southern Africa, Biennial Conference, 4-7 May, Baxter Theatre
Centre, Cape Town.
A FOURIE, B TH VERHAGEN, M LEVIN and H D ROBINSON (1998) Tritium as an indicator of
contamination from landfill leachate. Wastecon í98, 13-15 October, Kempton Park.
M LEVIN and B TH VERHAGEN (1999) A unique approach to evaluate the utility of landfill
monitoring boreholes. ISSMGE, 12th African Regional Conference, Geotechnics for developing
Africa. 25-27 October, Durban.
B TH VERHAGEN, D B BREDENKAMP, H JANSE VAN RENSBURG and J L FARR (1999)
Recaharge quantification with radiocarbon: independent corroboration in three Karoo aquifer studies
in Botswana. In: Procs International Symposium on Isotope Techniques in Water Resources
Development and Management. IAEA, Vienna
B TH VERHAGEN (1999) Isotope hydrology in Africa. In: Procs 11th International Conference of
the Geological Society of Africa. Cape Town, South Africa.
M J BUTLER (1998) Ground water pollution at sanitarylandfill sites: Geohydrological,
environmental isotope and hydrochemical studies. MSc Dissertation (Geology) University of the
Witwatersrand, Johannesburg.
M J BUTLER and B TH VERHAGEN (1999) Trutium in waste as a tracer of landfill leachate in
surface and ground water in South Africa. Poster presentation in: Procs International Symposium on
Isotope Techniques in Water Resources Development and Management. IAEA, Vienna
Papers at International Conferences. 1998-1999
1
Fifteenth Int. Conference on the Application of Accelerators in Research and Industry,
University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M.
Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza, Accelerators and nondestructive measurement in the minerals industry (Invited paper).
16
2
Fifteenth Int. Conference on the Application of Accelerators in Research and Industry,
University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M.
Ambrosi,. H. Rahmanian and J. Guzek,, Experimental verification of computer image
formation in accelerator fast neutron radiography (Invited paper).
3
Fifteenth Int. Conference on the Application of Accelerators in Research and Industry,
University of North Texas, Denton, Texas, November 1998, R. M. Ambrosi and J. I. W.
Watterson, The relationship between contrast, resolution and detectability in fast neutron
radiography.
4
Fifteenth Int. Conference on the Application of Accelerators in Research and Industry,
University of North Texas, Denton, Texas, November 1998, H. Rahmanian and J. I. W.
Watterson, Neutron energy discrimination using a proton radiator and a phosphor layer.
Publications in Refereed Journals and Conference Proceedings
(Recognised by the S. African Department of National Education)
1. J. Guzek, K. Richardson, C.B. Franklyn, A. Waites, W. R. McMurray, J. I. W. Watterson and U.
A. S. Tapper Development of a high pressure deuterium gas target for the generation of intense
mono-energetic fast neutron beams. Nucl. Instr. and Methods in Phys. Res. ? (1998) ?-?
2. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza,
Accelerators and non-destructive measurement in the minerals industry. Applications of
Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference,
Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings,
In Press.
3. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian and J. Guzek, Experimental verification of
computer image formation in accelerator fast neutron radiography. Applications of Accelerators
in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas,
November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
4. R. M. Ambrosi and J. I. W. Watterson, The relationship between contrast, resolution and
detectability in fast neutron radiography. Applications of Accelerators in Research and Industry,
Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L.
Duggan and I. L. Morgan eds, AIP Conference Proceedings, (1999) 1078 - 1083.
5. R.M. Ambrosi, J.I.W. Watterson, The effect of air cavities on the dose delivered to the lung
during high-dose brachytherapy. Biological Trace Element Research vols 71 – 72 (1999) 499507
6. H. Rahmanian and J. I. W. Watterson, Neutron energy discrimination using a proton radiator and
a phosphor layer. Applications of Accelerators in Research and Industry, Proceedings of the
Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L.
Morgan eds, AIP Conference Proceedings, In Press.
Patents
1
U. A. S. Tapper, G.W. Over, J Guzek, H. Rahmanian and J. I. W. Watterson, Scintillation
detector, S.A. Patent 95/5218.
17
2
U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron beam generator, S.A. Patent
95/7686.
3
K. Richardson, U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron radiography
gas target, S.A. Provisional Patent H0613.224.
18
ION IMPLANTATION AND SURFACE STUDIES RESEARCH PROGRAMME
Leader: Prof. T.E. Derry, Reader in Ion-Crystal Interactions, Physics Department.
Participating academics:
________________________________________________
name
|department
| time spent
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(Prof) T.E. Derry
|Physics
| 50 %
(Prof) J.F. Prins*
|Schonland (sec) | 90 %
(Prof) J.D. Comins
|Physics
|
5%
(Dr) G. Hearne
|Physics
|
5%
(Prof) A.T. Davidson |Zululand Univ. |
(Prof) V. Hoffmann
|Tübingen Univ. |
---------------------------------------------------------------------
* note -- Prof. Prins is seconded from De Beers, whose Diamond Electronics Programme he manages,
and although attached to the Ion Implantation & Surface Studies Research Programme, he
directs his research independently, making use of our facilities.
19
Objectives & Rationale:
(1) To promote research which is already well-established at the SRCNS, on ion-beam modification
and/or ion beam analysis (supplemented by other spectroscopies) of the (near) surface of
technologically important and fundamental solids -- diamond, metals, ionic crystals, catalysts, and
other materials. The principal research instruments are an ion implanter, small accelerator and UHV
surface-science chamber, interconnectable.
(2) To foster the existing collaborations with industries, other institutions (including HBU's) and
internationally. The Schonland ion-implantation group provides a centre of both equipment and
expertise for the research of others, as well as its own. The research provides a springboard for
overseas collaborations, via both overseas visits and visitors from overseas.
(3) To continue to train postgraduate students, who find our combination of pure and applied physics
stimulating, and to provide a variety of undergraduate projects for students of all races. Some dozen
research students have now graduated, many finding ready employment in industry.
The past year has been a successful one, with Prof. Prins publishing many research and review
papers, and rapidly becoming an invited celebrity on the international conference circuit. Prof. Derry
was elected to the Fellowship grade of the British Institute of Physics.
20
Research Projects:
1 (a) Investigation of the amount and position of oxygen atoms on diamond surfaces
Using Rutherford backscattering and resonant ion scattering, and transmission channelling.
Personnel: T.E. Derry, D.B. Rebuli (student), plus WNAC members
The research has possible implications for the chemical-vapour deposited diamond layer industry. Mr
D Rebuli has obtained his M.Sc and written several papers (see publications lists).
(b) Functional form of the oxygen on diamond surfaces
Using fourier transform infra-red spectroscopy; a collaboration with Tübingen University.
Personnel: T.E. Derry, V. Hoffmann (Tübingen)
A sabbatical by T.E. Derry (February-July 1998) initiated this work, which has continued with
another brief visit to Tübingen in 1999. The results so far are promising.
2 (a) Attempt to produce carbon (diamond) epitaxy on copper single crystals
Using ion implantation, Auger spectroscopy, possibly ion channelling.
Personnel: J.F. Prins, S.R. Naidoo (student)
This is an industry collaboration (De Beers); success would be the key to the diamond semiconductor
industry, and would place South Africa at the forefront. Work continued in 1998 using the upgraded
Auger hardware and software.
(b) Improvement of diamond doping
Using ion implantation and electrical measurements, plus development of the theory.
Personnel: J.F. Prins, S.R. Naidoo (student), H. van Heerden
A further industry collaboration (De Beers) with a view to developing the next millennium’s diamond
semiconductors. Both p- and n-type doping (using B and P respectively) continue to be improved,
and good n-type doping using oxygen implants has recently been patented. Prof. Prins will seek
further improvement using high-energy implants in the U.K.
(c) Electron-injection junctions and blue luminescence in diamond
Using implantation, electrical measurements.
Personnel: J.F. Prins, S.R. Naidoo (student)
Industry collaboration (De Beers); part of the diamond semiconductors studies. Some of the work has
been published during the review period.
(d) Metal-insulator transition in heavily doped diamond
Using ion implantation and electrical measurements
Personnel: M.J.R. Hoch, J.F. Prins, T.S. Tshepe (student)
A collaboration with members of the Physics Dept. Results have been published in papers and at
conferences.
3 (a) Radiation damage in other substances: ionic oxides
Using ion implantation and optical spectroscopy.
Personnel: A.T. Davidson (Zululand) + students, T.E. Derry, J.D. Comins
This represents our continuing University of Zululand collaboration.
(b) Radiation damage in silicon
Using ion implantation, surface Brillouin scattering.
21
Personnel: J.D. Comins and other members of Physics Dept, T.E. Derry, X. Zhang (student)
This collaboration with the Physics Dept has produced both journal and conference papers.
(c) Implantation and radiation damage in InSnO4
Using both low and high energy implantations (the latter with the 1,4 MeV accelerator).
Personnel: J.D. Comins, T.E. Derry, G. Amolo (student)
This Physics Dept collaboration is relatively new.
4 (a) Attempt to synthesize the postulated ultrahard material C3N4
Proposed method: ion implantation, surface Brillouin scattering analysis of the layers.
Personnel: S.B. Luyckx, J.D. Comins, T.E. Derry, J.F. Prins
The original collaboration with the Physics Dept has been on a back-burner, but some promising
results have been obtained by Prof. Prins.
(b) High pressure diamond anvil cell studies
Assisted by ion implantation of electrical contacts into the cell.
Personnel: G. Hearne + students, S.R. Naidoo, T.E. Derry
Another collaboration in progress with the Physics Dept.
5(a) Metal alloying and defects
Using implantation, Mössbauer, ion channelling.
Personnel: H. Pollak, T.E. Derry, J.K. Dewhurst (student), H. de Waard (Groningen)
This interesting cross-disciplinary project with overseas networking had initial success, but is now
concluded with the decease of Prof. Pollak.
(b) Tungsten carbide studies
Using ion implantation or ion beam analysis.
Personnel: T.E. Derry, S.B. Luyckx.
Recent work for Boart Longyear (both here and in Ireland) has involved the ion-beam analysis of
trace amounts of boron in their and others’ product.
(c) Surface engineering for industry
Using ion implantation
Personnel: T.E. Derry, H. van Heerden, S.B. Luyckx
There are industry collaboration possibilities here if the FRD/NRF were to facilitate and maintain
industrial enthusiasm, but no new projects have been offered as yet.
6 Synthesis and promotion of catalysts by novel routes
Using ion implantation (including into powders), XPS.
Personnel: N.J. Coville (Chemistry), T.E. Derry, H. van Heerden
A project with cross-disciplinary networking and industry collaboration, which was very active in the
past, and still of potential interest to the Chemistry Department.
7 Services to continue:
Support of other universities by provision of service implants (e.g. Pretoria, Cape Town, DurbanWestville): regularly continuing.
Availability of the UHV electron spectrometer for surface analyses by othe (paying) institutions.
22
Ion Implantation and Surface Studies Research Programme
plus collaborators
PUBLICATIONS FOR 1998:
WJ Huisman, M Lohmeier, HA van der Vegt, JF Peters, SA de Vries, E Vlieg, VH Etgens, TE Derry,
JF van der Veen.
Evidence for Tilted Chains on the Diamond(111)-2x1 Surface Surface Science 396, pp 241-252
X Zhang, JD Comins; AG Every, PR Stoddart, W Pang, TE Derry
Surface Brillouin Scattering Study of the Surface Excitations in
Amorphous Silicon Layers Produced by Ion Bombardment
Physical Review B 58, 13677-13685
X Zhang, JD Comins, AG Every; PR Stoddart, W Pang, TE Derry
Study of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin Scattering
Proceedings of the 16th International Conf on Raman Spectroscopy, September 1998, pp 884-887
JF Prins
Recombination Luminescence from Defects in Boron-ion Implantation-doped Diamond
using Low Fluences
Materials Research and Innovations 1, pp 243-253
JF Prins
Ultraviolet Cathodoluminescence from Diamond Layers after Doping
by means of Boron-ion Implantation
Applied Physics Letters 73, pp 2308-2310 (1998)
JF Prins
Ion Implantation of Diamond Below the Amorphization Threshold:
Defects, Impurities, and their Interactions
Proceedings of the 5th NIRIM International Symposium on Advanced Materials,
Tsukuba, March 1998; publ National Institute for Research in Inorganic
Materials, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; pp 93-96
JF Prins
Recent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of
Ion Implantation
Diamond Films and Technology 8, 181-194 (1998)
JF Prins
Doping of Diamond by the Diffusion of Interstitial Atoms into Layers Containing a Low Density of
Vacancies
Diamond and Related Materials 7, 545-549 (1998)
23
JF Prins
Ion Implantation of Diamond Below the Amorphization Threshold:
Defects, Impurities, and their Interactions (invited paper)
5th NIRIM International Symposium on Advanced Materials, Tsukuba, March 1998
JF Prins
Recent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of
Ion Implantation (invited paper)
Name of Journal/Book/Magazine/Report/Conference
2nd International Symposium on Diamond Electronic Devices, Osaka,
March 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JPF
Sellschop
Oxygen on Diamond Surfaces
SAIP Conference, Cape Town, July 1998
T Tshepe, JF Prins, MJR Hoch
Conductivity Studies in Boron-ion Implanted Type IIa Diamond
SAIP Conference, Cape Town, July 1998
SR Naidoo, JF Prins
Carbon Overgrowths on Copper by Ion Implantation
SAIP Conference, Cape Town, July 1998
WJ Huisman, JF Peters, SA de Vries, E Vlieg, JF van der Veen, TE Derry
Synchrotron Radiation Determination of Atomic Positions on the Diamond(111) Surface Before and
After Reconstruction
Annual Diamond Conference, London, July 1998
JF Prins
Activation of, and Vacancy Interactions with, Large Dopant Atoms in Diamond
Annual Diamond Conference, London, July 1998
E Sideras-Haddad, D Rebuli, TE Derry, SH Connell, JPF Sellschop, BP Doyle, RD Maclear,
Oxygen on Diamond
Annual Diamond Conference, London, July 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JM
Butler, JPF Sellschop
Oxygen Surface Studies in Ultra-thin Diamonds using Transmission Channelled Rutherford Forward
Scattering
International Microprobe Conference, Cape Town, August 1998
DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF Sellschop,
Oxygen on Diamond Surfaces
International Conference on New Diamond Science and Technology, Pretoria, September 1998
24
SR Naidoo, JF Prins
Electroluminescence from Electron Injection Junctions Created by Carbon and Phosphorus Ion
Implantation
International Conference on New Diamond Science and Technology, Pretoria, September 1998
T Tshepe, JF Prins, MJR Hoch
Metal-Insulator Transition in Boron-Ion Implanted Type IIa Diamond
International Conference on New Diamond Science and Technology,
Pretoria, September 1998
X Zhang, JD Comins,’ AG Every, PR Stoddart, W Pang’ TE Derry
Study of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin Scattering
16th International Conference on Raman Spectroscopy, Cape Town, September 1998
PUBLICATIONS FOR 1999:
D Rebuli, P Aggerholm, JE Butler, SH Connell, TE Derry, BP Doyle, RD Maclear, JPF Sellschop, E
Sideras-Haddad
Oxygen Surface Studies in Ultra-thin Diamond Using a Resonance Reaction and Transmission
Channelled Rutherford Forward Scattering
Nuclear Instruments and Methods B158 (1999) 701-705
DB Rebuli, TE Derry, E Sideras-Haddad, B Doyle, RD Maclear, SH Connell, JPF Sellschop,
Oxygen on Diamond Surfaces
Diamond and Related Materials 8 (1999) 1620-1622
SR Naidoo, JF Prins
Electroluminescence from Electron Injection Junctions Created by
Carbon and Phosphorus Ion Implantation
Diamond and Related Materials 8 (1999) 1502-1507
T Tshepe, JF Prins, MJR Hoch
Metal-Insulator Transition in Boron-Ion Implanted Type IIa Diamond
Diamond and Related Materials 8 (1999) 1508-1510
SR Naidoo, JF Prins
Raman and Auger Spectroscopy Studies on Ion Implanted Diamond
SAIP Conference, Port Elizabeth, July 1999
G Amolo, JD Comins, DS McLachlan, TE Derry
Structural Damage of Tin-doped Indium Oxide (ITO) by 1MeV Protons
SAIP Conference, Port Elizabeth, July 1999
JF Prins
Metastable Dopant States in Diamond
Annual Diamond Conference, Oxford, July 1999
25
T Tshepe,JF Prins, MJR Hoch
The Metal-insulator Transition in Diamond
Annual Diamond Conference, Oxford, July 1999
JF Prins
Oxygen Donor States in Diamond
Annual Diamond Conference, Oxford, July 1999
JF Prins, TE Derry
Radiation Defects and their Annealing Behaviour in Ion Implanted
Diamonds (invited paper)
10th Internat Conf on Radiation Effects in Insulators, Jena, July 1999
JF Prins
Functional Materials: Physics and Chemistry of Semiconductors: Diamond
Encyclopaedia of Materials: Science and Technology (in press)
Chapter in Book
JF Prins, TE Derry
Radiation Defects and their Annealing Behaviour in Ion-implanted Diamond
Nuclear Instruments and Methods (in press)
Conferences and visits
(1) 5th NIRIM International Symposium on Advanced Materials, Tsukuba (Japan) March 1998
Attending: J.F. Prins (chairman, presenter)
(2) 2nd International Symposium on Diamond Electronic Devices, Osaka (Japan), March 1998
Attending: J.F Prins (chairman, presenter)
(3) European Materials Research Society Spring Meeting, Strasbourg (France), June 1998
Attending: T.E. Derry
(4) Annual Diamond Conference, London (UK), July 1998
Attending: J.F. Prins, T.E.Derry (both presenting)
(5) South African Institute of Physics Conference, Cape Town, July 1998
Attending: D.B. Rebuli (presenter), S.R. Naidoo.
(6) International Microprobe Conference, Cape Town, August 1998
Attending: D.B. Rebuli (presenter)
(7) International Conference on New Diamond Science and Technology, Pretoria, Sept 1998
Attending: J.F. Prins (Organizing Committee Chairman), T.E. Derry, D.B. Rebuli, S.R. Naidoo (all
presented papers).
(8) South African Institute of Physics Conference, Port Elizabeth, July 1999
Attending: S.R. Naidoo, G. Amolo (presenting), T.E. Derry (chairing).
26
(9) Annual Diamond Conference, Oxford (UK), July 1999
Attending: J.F. Prins (presenter).
(10) 10th Internat Conf on Radiation Effects in Insulators, Jena (Germany), July 1999
Attending: T.E. Derry (presenter).
T.E. Derry spent the period from February to July 1998 on study-leave at the University of Tübingen
(Germany) helping to set up measurements to reveal the environment of the hydrogen and oxygen (or
other) atoms on polished diamond surfaces using infra-red spectroscopy.
Post-graduate Students
0910017O S.R. Naidoo (M.Sc now converted to Ph.D), registered Jan 1995 (part-time).
Topic: Carbon overgrowths on copper by ion implantation, supervisor: J.F. Prins
9201400E D.B. Rebuli (M.Sc), registered Jan 1996, submitted and degree granted 1999.
Topic: "Ion Beam Analysis of Oxygen on Diamond Surfaces", supervisor: T.E. Derry.
27
Annual Report 1998-99 for Research Programme
Based at the Schonland Research Centre
1. Name of programme
4.3.1. Nuclear Physics Programme
2. Programme Leader
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department)
3. Members of the Nuclear Physics Group Pursuing the Programme
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department, Wits,
1999)
Dr J. Carter (Senior Lecturer, Physics Department, Wits, Staff number
spent on research activities 35%)
resigned June
603953, percentage time
Dr. R.W. Fearick (Senior Lecturer, Physics Department, UCT).
 Professor B. Spoelstra (Physics Department, University of Zululand).
The members of the Nuclear Physics Group have enjoyed a longstanding and ongoing collaboration
which includes the corresponding groups at the National Accelerator Centre, Faure, the Florida
State University, USA, the Triangle Universities Nuclear Laboratory, USA, and the Technical
University, Darmstadt, Germany.
4. Research Projects
(a) Professor V. Hnizdo (principal investigator)
(i)
Research into the implications of the so-called hidden mechanical momentum of
macroscopic bodies in classical electrodynamics has continued, yielding a series of papers
in the American Journal of Physics.
(ii)
A major calculational study of the geometric factors in the classic analysis of the
masurability of the electromagnetic field of Bohr and Rosenfeld has been published.
Using the calculational methods of this paper, the electromagnetic “self-force” on a
spherical test body has been evaluated in closed form, which enabled us to refute the
conclusions of a recent revision of the Bohr-Rosenfeld analysis that were at variance with
the results of the latter work.
(iii)
The continuing investigation into nuclear structure effects in light heavy-ion scattering
reactions was carried out at the Tandem accelerator of the Schonland Centre. This led to
the award of an MSc degree to J. Madonsela in December 1998.
28
(b) Dr J. Carter (principal investigator)
5.
(i)
Data were obtained in 1997 at the Cyclotron Facility of the National Accelerator Centre in
the latest of a series of experiments investigating the excitation and decay of giant
resonances in nuclei. This involved the participation of colleagues from Darmstadt.
Subsequent data analysis was undertaken during a sabbatical visit of three months to
Darmstadt in 1998 and a another visit of one month in 1999. This work is currently being
prepared for publication.
(ii)
An ongoing programme of light heavy-ion scattering is being pursued at the Tandem
accelerator, Schonland Centre. Recently two major publications were produced, one
associated with a PhD degree and one with an MSc. The present work involving the
scattering of 9Be from 9Be together with existing data will lead to the third paper.
Publications 1998-99

V. Hnizdo, “Covariance of the total energy-momentum four-vector of a charge and current
carrying macroscopic body,” American Journal of Physics 66 (1998) 414-418.

J. Carter, A.A. Cowley, H. Diesener, R.W. Fearick, S.V. Förtsch, M.N. Harakeh, J.J.
Lawrie, S.J. Mills, P. von Neumann-Cosel, R.T. Newman, J.V. Pilcher, A. Richter, K.
Schweda, F.D. Smit, G.F. Steyn, S. Strauch and D.M. Whittal, “Isoscalar quadrupole
strength in 40Ca from the (p,p’o) reaction at Ep = 100 MeV,” Nucl. Phys. A 630 (1998)
631.

V. Hnizdo, “Radiation from circling relativistic charges, comment on a paper by
Gordeyev,” Am. J. Phys. 66 (1998) 847.

V. Hnizdo, “Comment on: An exactly solvable two-body problem with retarded
interactions and radiation reaction in classical electrodynamics,” J. Math. Phys. 39 (1998)
5663.

V. Hnizdo, “Common misrepresentation of the Einstein-Podolsky-Rosen argument,”
Found. Phys. Lett. 11 (1998) 359-370.

V. Hnizdo, “Geometric factors in the Bohr-Rosenfeld analysis of the measurability of the
electromagnetic field,” J. Math. Phys. 32 (1999) 2427-2445.

V. Hnizdo, “Comment on ‘Limits of the measurability of the local quantum
electromagnetic field amplitude, ” Phys. Rev. A, in press (1999).

V. Hnizdo, “On the Laplacian of 1/r,” Eur. J. Phys., submitted (1999).

H. Diesener, U. Helm, H. Miska, P. von Neumann-Cosel, A. Richter, G. Schrieder, A.
Stascheck, A. Stiller, H.J. Emerich, G. Fricke, T. Kroehl and J. Carter, “Giant resonance
spectroscopy of 40Ca with (e,e’x) reaction (I): Experiments and overview of results,” Phys.
Rev. C, submitted (1999).
29

H. Diesener, U. Helm, V. Huck, P. von Neumann-Cosel, C. Rangacharyulu, A. Richter, G.
Schrieder, A. Stascheck, S. Strauch, J. Ryckebusch and J. Carter, “Giant resonance
spectroscopy of 40Ca with the(e,e’x) reaction (II): Multipole decomposition of 4
integrated spectra and angular correlations,” Phys. Rev. C, submitted (1999).

H. Diesener, U. Helm, G. Herbert, P. von Neumann-Cosel, A. Richter, G. Schrieder, S.
Strauch and J. Carter, “Giant resonance spectroscopy of 40Ca with the (e,e’x) reaction (III):
Semidirect versus statistical decay,” Phys. Rev. C, submitted (1999).

B.M. Nangu, J. Carter, H. Machner, B. Spelstra, J. Pilcher, E. Sideras-Haddad, S.H.
Connell, J.P.F. Sellschop, A.A. Cowley, D. Aschman, D. Steyn and K. Baruth-Ram,
“Energy deposition and the origin of intermediate-mass fragments in mdedium-energy
proton induced reactions,” in preparation.
6. Conferences and Visits
(i) V. Hnizdo: Research visit to Florida State University, Tallahassee, July 1998
(ii) J. Carter: Research visits to the Nuclear Physics Institute, Technical University, Darmstadt
July/August/September 1998 and June/July 1999
7. Visiting Scientists
(i) Dr S.V. Förtsch, National Accelerator Centre, August 1999
30
8. Higher-degree students 1998-99
Student
Name
Degree
number
First
Completion
Topic
Supervisor
Registration
9411102A
J Madonsela
MSc
Mar 93
Nov 98
Nuclear
V Hnizdo
9213310A
B M Nangu
MSc
Feb 92
2000
Nuclear
J Carter/B Spoelstra
Part-time
MHLNCE001
N W Mhlahlo
MSc
Jan 98
2000
Nuclear
R W Fearick
MBLGIV00X
G.K Mabala
PhD
Jan 98
2001
Nuclear
R W Fearick
MRRSEA003
S H T Murray
MSc
Jan 98
2000
Nuclear
R W Fearick
Dr J. Carter
September 1999
31
Report of the
WITS-Northern Accelerator Research Centre
within the
Schonland Research Centre for Nuclear Sciences
32
Description of the Research Centre ..................................................................................34
Group Membership ............................................................................................................36
Research Projects ...............................................................................................................37
Accelerator Laboratory Facilities ......................................................................................51
Usage..................................................................................................................................54
Publications ......................................................................................................................56
Conferences and Visits .....................................................................................................60
Visiting Scientists .............................................................................................................67
Students .............................................................................................................................68
Version of 13.8.98
33
The WITS-Northern Accelerator Research Group
(Director : Dr SH Connell)
The WITS-Northern Accelerator Research Centre research entity provides a common home for a
range of research groups spanning basic physics, applied physics, industrial physics and various
interdisciplinary sciences, such as nuclear geology and nuclear techniques in industry, bio-medicine,
metallurgy and the environment.

The Particle-Solid Interactions Research Group
(Leader : Dr SH Connell) : focuses on the phenomena associated with the interaction of
accelerated beams and radiation with ordered materials. In the case that the material properties
are well understood, then the basic physics aspects of the interaction are studied. In the inverse
situation, the goal is materials physics. In all cases the research methodology involves accelerated
beams, nuclear instrumentation, highly automated computer controlled data acquisition and
processing, sophisticated engineering in the equipment construction and finally data
interpretation via simulation of the experimental observables based on modern quantum
mechanical models. Most of the work is carried out at the SRCNS, but where appropriate, regular
use is made of CERN, TRIUMF, PSI and other major international facilities.

Nuclear-Interdisciplinary Science based on Ion-Beam Microscopies
(Leader : Dr E Sideras-Haddad) : applies nuclear and atomic physics phenomena in the
interaction of focused beams with small samples to perform a range of novel microscopies in
collaborative interdisciplinary research projects. Accelerator Mass Spectrometry capability is
currently being developed

The Nuclear Diamond Physics Research Group
(Leader : Prof JPF Sellschop) : focuses particularly on new physics and resulting applications in
specific areas at the interface of nuclear and diamond physics. Most of the work is carried out at
the SRCNS, but where appropriate, regular use is made of CERN, TRIUMF, PSI, Grenoble, GSI
Darmstadt and other major international facilities.

The Nuclear Geology Research Group
(Leader : Dr RJ Hart) : pursues global geological topics relevant to modern theories of crustal and
earth forming processes. Primarily geologists, they benefit from the synergy of a close
association with novel nuclear techniques for a vital part of their sample characterisation.
The synergy, mutual operation and interdependence between these research groups includes the
following points:

Nuclear and particle physics knowledge is either a goal or an important tool of the research
thrust.

Nuclear techniques (accelerated particle beams, radioactivity, nuclear electronics and detection
systems and computer systems for data processing, visualisation and process control) are used in
the research programmes.
34

Common major facilities. The most important major equipment items here are the two Van de
Graaff accelerators with their associated infrastructure.

Postgraduate student training. The research group leaders believe the open environment of a
large research facility facilitates the development of students due to the points mentioned above.

Coherence. The whole is greater than the sum of the parts.
35
Group Membership
Name
Department
Staff No.
Percentage Time
Dr SH Connell
Physics : Senior
Lecturer
08800031
40% lecturing
25% Lab Management
35% Research
Dr E SiderasHaddad
Physics : Senior
Research
Officer
00675961
30% lecturing
25% Lab Management
45% Research
Prof JPF Sellschop
Dr RJ Hart
Physics :
Emeritus
Professor
00911272
Secondment :
Council of
Geosciences
09000631
75% Research
25% National Advisory
Committees
40% Research
15% CGS line function
25% Lab Man
20% International
Collaboration
36
Research Projects
Impurity Chemistry and Dynamics in Diamond by In-beam Molecular Complex Spectroscopy
Staff :
SH Connell, JPF Sellschop, E Sideras-Haddad.
Students :
MG Bossenger, BP Doyle.
Collaborators : H Appel (KFK Karlsruhe), K Bharuth-Ram (UDW), W Verwoerd (UNISA).
This work involves basic research into the behaviour of defects and impurities in insulators and wideband gap semiconductors. Defects and impurities play an important role in determining the physical,
electrical, optical and chemical properties (among others) of materials. Using the EN-Tandem
Accelerator, radioactive impurities are recoil-implanted into materials to study their geometrical,
chemical and dynamical relationships in the host lattice and as complexes with other defects. A
unique opportunity to visualise transient and stable molecular complexes formed immediately after
ion-implantation is afforded (hot-atom chemistry). The data is reconstructed using the details of the
hyperfine interaction of the probe nucleus with local fields. Diamond, other carbon allotropes, as well
as various carbon containing molecules have been targeted as important materials for research.
During the review period, attention has focused on analysis of previous data, writing papers, design
and fund-raising for development of a heavy-ion pulsing system for the EN-Tandem (THRIPP
program with DeBeers) as well as organising the 11th International Conference on Hyperfine
Interactions at the end of August 1998.
Impurity Chemistry and Dynamics in Diamond by Perturbed Angular Correlations
Staff :
SH Connell, JPF Sellschop, E Sideras-Haddad.
Students :
BP Doyle, EJ Storbeck
Collaborators : K Bharuth-Ram (UDW), H Pattyn (Leuven), W Verwoerd (UNISA), U Wahl (Leuven)
This is the off-line source based activity version of the previous measurements, enabling later time
windows to be accessed, allowing solid-state reactions to occur. A PAC project on 111In in diamond is
ongoing as a complementary technique to the CEEC measurements mentioned further on. A new
PAC facility has been developed. Conventional systems rely on many crates of fast electronics to
process the signals. Our system is novel in that buffered event-by-event acquisition (COLLECT - see
later section), enables software logic to extensively replace the expensive hardware systems, while
still maintaining the data-rate of the larger systems. The project has been given a large boost with
access being granted to the ISOLDE facility, CERN, Switzerland for implantation of exotic
radioactive species. New software for the analysis of this data is being developed. These analyses are
compared to the CEEC data taken on the same systems, and with theoretical calculations that have
been made in collaboration with the Physics Department. Subsequently double implant experiments
will also be done with the aim of studying the dynamical behaviour of In-X complexes. The PAC
technique can label various complexes and follow their behaviour through various sample treatments
with particularly simple sample preparation for the measurement process. These studies illuminate
processes of diffusion, decoration, complexation, dissociation, trapping and detrapping in the solid
state. This information is relevant to processes which lead to doping, passivation and poisoning
phenomena in semi-conductors (in our case, semi-conducting diamond). There was substantial
experimental activity during the year, and the results are being presented at the conference mentioned
above, as well as being prepared for more detailed exposure in journals.
37
Positron Spectroscopy studies of pure diamond, dilute bulk defects and surfaces.
Staff :
SH Connell, JPF Sellschop.
Students :
RWN Nilen, CG Fischer
Collaborators :A Alam (Bristol), W Anwand (Rosendorf), K Bharuth-Ram (UDW), G Brauer
(Rossendorf), DT Britton (UCT), P Coleman (East Anglia), F Malik (East Anglia), K
Maier (Bonn, J Major (MPI-Stuttgart), A Seeger (MPI-Stuttgart), E Sendezera (U
Zululand), H Stoll (MPI-Stuttgart), W Verwoerd (UNISA).
Positrons implanted into solids thermalise, diffuse rapidly, and finally form well defined
configurations with the host lattice or its defects. Observation of the properties of the annihilation
radiation allows a reconstruction of the local microscopic configuration by means of quantum
mechanical models. In this way, detailed information concerning solid state parameters is measured.
Spectra taken for the diamond host matrix demonstrate severe and hitherto unexplained anomalies.
This anomalous behaviour of the positron in diamond has now been resolved following our
measurements, calculations, and the calculations of our collaborators. Many papers have been
published or are in preparation, including a review article. Following these advances, our programme
has broadened from the positron-pure-bulk-diamond interaction to the studies of positron-defect and
positron-surface interactions. A detailed set of experiments probing lattice effects in extended damage
transport during ion-implantation, photochromic defects and surface structures as well as near-surface
defects has been performed this year. The results are currently being published and prepared for
publication.
Conversion electron emission channeling spectroscopy
Staff :
SH Connell, JPF Sellschop.
Students :
BP Doyle, EJ Storbeck.
Collaborators :K Bharuth-Ram (UDW), H Hofsass (Konstanz), H Pattyn (Leuven), W Verwoerd
(UNISA), U Wahl (Leuven).
Ion implantation in diamond of radioactive nuclides such as 111In can be exploited to provide
information on the environment in which the nuclide resides. In the emission of conversion electrons
from the nuclide at its characteristic lattice sites in the diamond, the electrons are sensitive to the
source-lattice configuration as well as the structure of the crystal through the channeling, blocking
and flux peaking effects. The CEEC research is entirely complementary to the PAC study mentioned
above, and the projects will be run simultaneously. The same comments apply then with respect to
future research, as in the PAC section. A two-dimensional position and energy sensitive PAD detector
was developed at CERN, Switzerland, originally as a high-energy physics tool, but now available to
CEEC measurements. This detector is the of its kind to be used in this way and now allows the rapid
collection of 2-dimensional channeling spectra. In two dimensions one is able to see both the axial
and planar effects in channeling, enabling a more complete picture of the impurity lattice site. A
profitable collaboration with K.U. Leuven has enabled the ISOLDE facility at CERN to be exploited
by us. This allows implantation of the radioactive probe ions to the stringent specifications required
for CEEC measurements. In order to explain the experimental results it is necessary to use solutions
to the quantum mechanical theory of electron channeling. This demanded the development of an
analysis program that takes into account the quantum nature of electron channeling. An important
recent contribution is the inclusion of molecular effects in the construction of the transverse
38
channeling potential, using Fourier methods based on the output from self-consistent quantum
chemical simulations of large diamond-like molecules. There is experimental evidence that this was
necessary, particularly in the case of channeling in diamond (<110> direction), where the electronic
structure is not well approximated by the normal methods based on atomic scattering factors.
Analysis of the large data sets obtained is well advanced. Results thus far indicate new perspectives
on the annealing of the implant damage and concur with recent density functional theory calculations
on the stable lattice site for the implanted and annealed In. This research is entirely complementary to
the PAC study mentioned above, and the projects have been run simultaneously. The same comments
as with regards future research apply here, as in the PAC section.
Muon Spin Rotation/Relaxation/Resonance (MSR) spectroscopy in diamond
Staff :
SH Connell, JPF Sellschop.
Students :
BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN Nilen
Collaborators :JM Baker (Oxford), K Bharuth-Ram (UDW), JE Butler (NRL-Washington), SFJ Cox
(Rutherford Lab), TL Estle (Rice U), T. Jestadt (Oxford). R Kiefl (TRIUMF), J Major
(MPI-Stuttgart), P. Murphy (Oxford), R Scheuermann (MPI-Stuttgart), A Seeger (MPIStuttgart),
Muonium-defect interactions as well as muonium dynamics are being explored using Muon Spin
Rotation/Relaxation/Resonance (MSR) spectroscopy. The current program takes advantage of the
unique properties of the muon to probe the behaviour of the hydrogen-like atom in diamond. The
importance of hydrogen as an impurity in diamond is widely appreciated. Its important catalytic role
in the metastable synthesis of diamond, as well as its anticipated significance regarding the electronic
properties of future diamond devices are two examples. Despite the relevance of hydrogen to
diamond growth, properties and engineering, comparatively little is known about it, and it has proved
to be a most difficult impurity to study using conventional techniques. On the other hand, most of the
information on hydrogen in diamond has been inferred by the indirect technique of the MSR, which
is sensitive, robust, accurate, and has a low background. Clear examples of muonium diffusion,
trapping and detrapping, and possibly even Ionisation reactions at B acceptors in semi-conducting
diamond have been both observed and modelled. The transparency of diamond and the
photochromicity of certain defects was used to illuminate some of the processes involved. A new
muonium site in diamond containing substantial amount of nitrogen-related defects was discovered.
This has provided evidence for a new deep trap for hydrogen in diamond, as well as a new way to
study one of the nitrogen related defects whose structure is much debated.
Thin diamond crystals - the doorway to new diamond physics
Staff :
SH Connell, JPF Sellschop, E Sideras-Haddad.
Students :
BP Doyle, IZ Machi, RD Maclear, DB Rebuli
Collaborators :P Aggerholm (Aarhus), M Rebak (DeBeers), J.E. Butler (NRL-Washington)
If thin, that is to say micron and sub-micron thickness, diamond of high quality, were to become
available it would make possible a large suite of research opportunities in both atomic and nuclear
physics, as we have long appreciated. Conventional polishing techniques become problematic for
thicknesses below 20 microns, owing to increasing difficulties with plastic deformation of the
diamond remnant. We have made substantial progress in this quest through a new approach : carbon
ions are implanted into a prepared diamond at an energy selected to place the Bragg peak at a depth
below surface corresponding to the thickness of the final diamond sliver required. A dose of incident
ions is delivered that is adequate to amorphise the layer corresponding to the Bragg peak. The
diamond is then heated to about 1200C to both make the amorphisation more complete and to restore
39
the crystal perfection of the superficial layer of any small amount of radiation damage by annealing.
This is followed by an electrochemical etch in pure water whereby the amorphous layer is removed,
allowing the superficial layer to float free. Special techniques are necessary to handle the sub-micron
to few-micron thick diamonds. In this manner we have successfully prepared diamond targets of 1 to
3 microns thickness.
Some of the new suite of research possibilities enabled by these exciting samples involves applying
any of Ion Beam Analysis (IBA) measurement technologies in channeling mode. This delivers lattice
structural information about defects and impurities, in addition to the normal analytical information.
Channeling Rutherford Backscattering Spectroscopy is used to study the details of the thin crystal
production process and to optimise it. Channelling-ERDA has been applied to identify hydrogen
structures in diamond. Transmission Channeling Forward Scattering is being used to study oxygen
termination structures on diamond.
A new concept in creating thin single crystal samples will shortly be explored in which the implanted
ion species is helium and the superficial layer is removed by the application of heat alone, as
successfully demonstrated in the case of silicon.
Hydrogen dynamics and chemistry by micro-scanned Elastic Recoil Detection Analysis
Staff :
SH Connell, JPF Sellschop, E Sideras-Haddad.
Students :
BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN Nilen, DB Rebuli
Collaborators :P Aggerholm (Aarhus) K Bharuth-Ram (UDW), JE Butler (NRL-Washington), E
Fritsch (Institut de Matériaux de Nantes)
Diamond has many physical and chemical properties attractive to the semi-conductor industry. The
presence of hydrogen in the diamond lattice influences these properties. Its presence is known to
affect the hardness of the material, it passivates active dopants and changes the optical transmission of
diamond. Theoretically, hydrogen is a simple example of an atom in a covalently bonded macromolecule, and is therefore instructive to model. The unique capability to perform 3-dimensional
microscopy of trace hydrogen distributions has been developed at the EN-Tandem accelerator to a
level of sophistication unmatched elsewhere in the world. This has enabled a coherent program
focusing on hydrogen dynamics and chemistry in diamond, supported as well by the other projects
using muons, positrons and radioactive ions described above. The new method has been called
ERDA (see the title of this section for expansion). In one programme of measurements, phenomena
like hydrogen stability, diffusion, trapping, detrapping, decoration, complexation and so on are
studied. In another set, hydrogen distributions were evaluated to characterise natural and synthetic
processes leading to hydrogen incorporation into diamond. This has relevance to metastable synthesis
of diamond as well as the natural genesis environment of diamond. This program has recently been
extended to include the channeling phenomenon, due to the availability of thin single crystal
diamond, as described in the previous research project. Channeling-ERDA measurements will give a
much improved picture of the crystallographic location of hydrogen in diamond. The possibility of
measuring the exact location of the hydrogen allows measurements of other important phenomena
involving hydrogen in the diamond lattice, for example, hydrogen diffusion pathways and
complexation modes with other defects.
40
European synchrotron radiation facility (Grenoble)
Staff :
JPF Sellschop, M Rebak
Collaborators :A Freund (ESRF)
Work over the past few years has continued in pursuit of using diamond in critically sensitive areas
in this powerful third generation radiation source. Diamond is usually compared with silicon and
germanium in its application as a monochromator for synchrotron radiation. Some of the physical
constants for which diamond is greatly superior to the other two are
 the linear absorption coefficient (and consequently the absorption length) for, say, 8 keV X-rays
diamond is enormously transparent for these wavelengths
 the Debye temperature for diamond is very high, and consequently the thermal vibration
amplitude is very low indeed
 the thermal expansion coefficient is very low
 the heat conductivity is very high
 the Darwin band width is small
The usually accepted figure of merit in such applications for diamond is some 600 times superior to
silicon, and 2000 times better than germanium. With the deployment of especially-grown diamond
with very small mosaic spread, tests have been carried out on the use of diamond as a high heat load
monochromator. Rocking curves confirmed the high quality of the diamond materials selected. In heat
load tests the rocking curve width remained constant over a wide range of beam intensities, quite
unlike silicon. The highest intensity, namely 3.5 kW / mm2, tested is to put it mildly most impressive,
since it corresponds to an energy density that exceeds that at the surface of the Sun !
Diamond proves to be radiation hard in this application also with very little evidence of damage over
prolonged periods of beam exposure. A second research thrust has been in an attempt to bend
diamond to provide saggital focusing of the monochromatised x-ray beam. A crystal bender was
especially designed, a diamond of high quality was configured to dimensions 10 mm x 5 mm x 67
micrometer with the large face the {111} orientation. This diamond was successfully and repeatedly
bent to a radius of curvature of 0.9 meter, giving a demagnification (focusing) factor of 20 times !
This field has proved to be a fruitful one and will be continued. Two invited papers were presented at
the recent SPIE conference in San Diego (July 1998).
Coherent, correlated phenomena resulting from the Incidence of High Energy Leptons and
Photons on Oriented Crystals
Staff :
SH Connell, JPF Sellschop.
Students :
ZZ Vilakazi
Collaborators :K Kirsebom (ISA-Århus), R. Medenwaldt (ISA-Århus), U. Mikkelsen (ISA-Århus), SP
Møller (ISA-Århus), E Uggerhøj (ISA-Århus), T Worm (ISA-Århus), S Ballestrero
(INFN-Florence), P Sona (INFN-Florence), K Elsener (CERN), YuV Kononets (RRC
Khurtarchov Institute), A Apyan (Yerevan Physics Institute), RO Avakian (Yerevan
Physics Institute), AE Avetisian (Yerevan Physics Institute), KA Ispiyran (Yerevan
Physics Institute), C Biino (INFN-Turin)
The Research programme is founded predominantly in fundamental Physics, embracing both the local
and the overseas capacity in a ordinated way. The scope of the research addresses all phenomena
associated with lepton-photon processes resulting from the incidence of ultra-relativistic particles on
highly-ordered crystalline materials. Scattering in a well aligned crystal geometry is extended to
investigate coherent and correlated versions of the basic theory of electromagnetic processes viz.
quantum electrodynamics (QED) at higher energies. QED is a highly developed field theory and has
been investigated experimentally to very stringent detail. In recent years it has become technically
41
possible to investigate QED processes in very strong crystalline electromagnetic fields. In short, new
phenomena and physics do arise, opening up a plethora of new concepts to be explored therein inter
alia Strong Field QED. This programme is undertaken at the CERN-SPS in the multi-national NA43
collaboration. The results show either very strong enhancements or losses in the cross-sections, as
well as changes in the shape of the cross-sections. This in turn leads to new phenomena, which
deepen an understanding of fundamental theories, as well as allowing new theoretical tests and new
applications. The NA43 experiment has essentially completed its brief. The investigations which were
carried out throughout the period that covered most of the period reported herein are: Establishing and
studying the occurrence of a very new effect, the production of linearly polarised, partially
monochromatic ultra-hard single photons by electron aligned incidence on crystals of very specific
relative orientation to the beam. Studying coherent enhancements in both pair-production and
brehmsstrahlung at ultra-relativistic energies. Realising and studying for the time in the laboratory
under well characterised conditions the occurrence of super-critical fields and their effect on energy
loss mechanisms. Studying channeling in bent crystals for super-relativistic particles. Most of these
new phenomena have lead to remarkable new devices which have already found application in other
High Energy Physics experiments, or are in a proposal stage which may lead to new HEP capabilities.
Of special mention : One new proposal is intended to lead to the use of the ultra-high energy
(polarised) photons produced as described above as a tool to study the gluon contribution to nucleon
spin. Another proposal would like to extract parasitic beam from the LHC accelerator for fixed target
experiments using bent diamonds.
Apart from the good physics delivered by the CERN programme, there has also been significant
technology transfer. The Physics Analysis Workstation (PAW) package was ported to a graphical
Linux-PC environment by S Ballestrero during a working visit of his to the SRCNS. This was the
time the entire CERN Libraries became available on PC in a graphical environment. Previously, only
mainframes or mini-computers could access the physics capability of this software. The port was
welcomed by the international (HEP) group and the CERNLIB's on Linux-PC's became officially
supported by the CERN Computer Group from then mn. S Ballestrero also developed a Data
Acquisition System (DAQ) that front-ends PAW to small lab detector systems. This gave the SRCNS
(and any other small lab) essentially the same data capture power as the large CERN experiments for
an incredibly reduced price. This innovation has been released via a WW page, and other labs are
now sharing in it. This development has allowed us to run the CERN Monte Carlo package GEANT
(which simulates many physics processes from keV to TeV interaction energies) and to contribute
effectively to the analysis of data taken at CERN in our own local environment, by having a local
PAW capability. It also enabled us to take the lead internationally in certain of our Physics
Experiments based locally at our microprobe. Part of this programme is discussed in a separate
section.
The Physics foothold at CERN will be extended when the ex-PhD student ZZ Vilakazi takes up a Post
Doc position on four CERN-HEP experiments later this year. An initiative to synergise our efforts
with the local theoreticians and other interested groups in other Universities in the country is in
progress.
42
Alkali Halide Materials and Super-Ionic Conductors
Staff :
DJ Comins, SH Connell, TE Derry, JPF Sellschop.
Students :
CG Fischer, RWN Nilen
Collaborators :
EJ Sendezera (U Zululand), AT Davidson (U Zululand)
The use of positrons as a microscopic probe for the investigation of defects in crystal and amorphous
systems, allows a study of the kinetics of creation and annealing out of defects. In particular, for the
Super-Ionic materials, an enhanced conductivity mechanism occurs which is not yet fully understood,
and is an issue of great current importance. An experiment using Positron Spectroscopy is being
developed as it is believed it can provide information on the role of vacancies in this phenomenon.
Non-Stochastic Ion-Implantation - Industrial Collaborative R&D
Staff :
SH Connell, JPF Sellschop.
Collaborators :
W Wesch (Jena), Leonard C. Feldman (Nashville)
The aim is to develop and study non-stochastic systems for maskless implantation of dopants for
situations of small feature size (<500 nm) and a large degree of integration (1x109 devices per chip).
The possibility of dopant implantation via shape pre-programmed raster scanning with highly focused
ion beams has already been postulated. We are exploring a non-stochastic method for maskless
implantation to improve device integrity.
The COLLECT Data Acquisition System
Staff :
SH Connell
Students :
BP Doyle, IZ Machi, RD Maclear
Collaborators :
S. Ballestrero (INFN-Florence)
COLLECT is a powerful multi-parameter data acquisition (DAQ) system, running on a Linux PC. It
was developed in order to serve the ever more complex data sets that are being taken at the SRCNS.
COLLECT front-ends to the Physics Analysis Workstation (PAW/PAW++), a powerful data
manipulation/visualisation tool, developed at CERN. The PAW system can be used as an online
presenter as well as for offline replay of the data. COLLECT therefore delivers the computing power
in DAQ previously known only on powerful computers at major high energy physics facilities to a PC
and CAMAC based system affordable by a small lab. COLLECT can be easily configured to any
desired experiment. Work is being done on a GUI version with a more easily configured CAMAC
event cycle and data n-tuple. This project was jointly funded by The University of the Witwatersrand
and The University of Durban Westville in South Africa. The system was published via the web, and
has been attracted much interest. For example, we recently received a request for it from CALTECH.
It has laid the foundation for a new generation of experiments at Schonland. For example, it enabled
the event reconstruction that allowed us to do micro-scanned imaging of trace hydrogen distributions
in diamond (discussed above). This capability attracted a director of an American Lab to do a 6 month
sabbatical at Schonland, which in turn led to additional foreign funding of the project by nearly R100
000.00. This is one of the technology transfers enabled by the CERN research programme (discussed
above).
43
The Schonland EN-Tandem Accelerator Control System
Staff :
AH Andeweg, JUM Beer, SH Connell, K Coone, E Rood JPF Sellschop, E SiderasHaddad.
Students :
RD Maclear
Collaborators :
P Aggerholm (Aarhus), M Hogan (NAC), F Weehuizen (NAC)
Currently the 6MV EN-Tandem of the Accelerator Laboratory at the Schonland Research Centre for
Nuclear sciences is being upgraded for control via a Graphical User Interface (GUI) computer system.
The system is based on distributed network control via an OS/2 network messaging system. Control
of the electronic equipment is done over a RS-232/RS-485 link to digital and analogue control
modules. The benefits of a computer controlled accelerator include: better quality ion beam; faster
set-up time; decreased operator reliance; increased accessibility to outside users; introduction of
intelligent control algorithms; automation of routine procedures; and upgrade of all power supplies.
The control program has the properties of using a high degree of commercially manufactured
software; is highly modular; based on object oriented programming code; is network based using
distributed intelligence; is highly customisable; exploits the messaging, prioritising, queuing and
resource sharing of the OS/2 operating system; and can be sequentially phased in with no major
equipment down-time. All the current power supplies will be replaced with modern, stable power
supplies. Control of the power supplies will be done using harsh environment capable
ADAM/NUDAM modules on a RS-485 drop-down network. The modules are extremely stable and
highly modular with only 3 types of modules needed to control all power supplies (analogue output,
analogue input and digital input/output). Voltage ramping of power supplies is built into the modules
and no extra code is needed for this. The modules connect directly to the RS-232 port of a PC and no
complicated interfaces or drivers are needed. The network messaging system, or Variable Table, is
used to broadcast instructions to the various power supplies. The table contains reference and actual
values for every control object in the network. The GUI console program updates the variable table
when a user wishes to change the value of a power supply. Notification queues notify clients (control
applications running on equipment-local computers) when a value in the table and changed, and the
required action is taken by the clients. Clients update the variable table when a value is read from a
power supply, and the GUI displays these values to the user. A relational SQL database is used for
storing all the information about the control system. The database is accessed by the variable table,
clients and user console at startup to retrieve this information. Based on this information, various
power supplies can be controlled in a predefined manner. The database also defines how the user
interface behaves and appears to the user. Expanding or modifying the system to include more control
objects or differently configured control objects is simply a matter of editing the database, not the
software.
Most of the systems software concepts have been developed at the National Accelerator Centre. Its
implementation at Schonland has been modified to further distribute intelligence in control
operations, display a higher reliance on cheaper modular commercial components and a greater
reliance on the GUI for the User interface. The design and implementation of the client programs, the
console program, the installation of the NAC-developed Variable Table, and the installation of the
commercial database and networking software has been part of the MSc and PhD program of the
student. The control electronics, cabling and cabinetry were developed by the technical staff.
44
Generic client control applications for the objects controlling Analogue input, output and digital
input/output have been written for these basic types of operations on power supplies modules. These
generic objects are resource file customised via the database to create a control application for any
given power supply, with no further programming (only editing of the accelerator database). The
server application accessed by these clients for communication with all the control modules belonging
to a single node via the COM port of a PC has been written. Instructions are passed to the server via a
prioritised queue, and extracted to the modules according to their priority in the queue. A Mark I user
interface has been written for testing the control of power supplies via the multiple-clients-server
system. All control electronics and new / modified stabilised power-supply implementations for the
hardware component of the control of the Duoplasmatron, the gas ion source of the accelerator
facility, have been completed. The Full Duoplasmatron electronics is therefore mounted into a single
rack and equipped with dummy loads, and connected to the node computer. This system has been
fully tested on the complete Duoplasmatron electronics rack using a standalone node computer. All
conceivable faults have been simulated, and the exception handling and error recovery have
functioned as planned. The speed of the system under load conforms to design specifications. We are
therefore ready to install the control node and electronics. Following a test and evaluation period
under running conditions, we will proceed sequentially to implement the entire 6-node control
system. Subsequent control nodes will be replications of this control node, customised by extending
the accelerator database. In preparation for this, the network-wide variable table communication
program has also been installed and is running over the OS/2 sub-network using NetBIOS. Networkaware database access has been established and implemented into the clients. The new control
console cabinetry has been designed and constructed and is currently being equipped with the
hardwired segment of the control-system (fast-safety systems, analogue feedback systems etc). We
expect to be operating with the control node later this year. We are investigating industrial interest in
this control system.
Heavy-ion Nuclear Reaction Mechanisms
Staff :
SH Connell, JPF Sellschop.
Students :
TG Stevens
Collaborators :V Allori (Milano), C Birattari (Milano), M Bonardi (Milano), M Cavinato (Milano), F
Cerutti (Milano), A Di Filippo (Milano), E Fabrici (Milano), E Gadioli (Milano), E
Gadioli Erba (Milano), SV Fortsch (NAC), JJ Lawrie (NAC), SJ Mills (NAC), FM
Nortier (NAC), I Schroeder (NAC), GF Steyn (NAC), AA Cowley (Stellenbosch).
Since January of 1993 this collaboration has been involved in a comprehensive study aimed at a better
understanding of the important mechanisms of heavy ion reactions and de-excitation in processes
initiated by projectile energies between the coulomb barrier and the fission threshold. A starting point
has been the concepts derived from the study of light particle induced reactions. These have been
extended with modification, as well as with the introduction of new concepts, to heavy ion induced
reactions. Experimentally we have studied the interaction of 16O and 12C, incident on the medium
mass, mono-isotopic 103Rh. We have adopted and developed the powerful activation technique to
obtain the comprehensive data set necessary to rigorously test the theoretical interpretation of these
reactions as developed by a group at the University of Milan. More than thirty reactions representing
excitation functions, angular distributions and residue recoil energy distributions over the entire
energy discussed above have been accumulated. In addition, this data set is accurate in absolute terms
to 20%. The uniform theoretical framework that has been gradually developed, is now capable of
describing the data to a remarkable degree. The processes of excitation described by a mean-field
approach, is considered separately to that of de-excitation where a time stepped Monte Carlo analysis
45
based on the Boltzman Master Equations is used. The matching of the theory to the data did not
proceed via adjustment of free parameters, but rather via careful selection of the major reaction and
de-excitation mechanisms. Finally we could conclude that the major reaction mechanisms include
only complete fusion, partial fusion of alpha like components, and proton and neutron transfer. The
de-excitation requires pre-equilibrium emission to be considered over the whole energy range as well
as ultimately statistical emission from the equilibrated nucleus. The mean field energy evolution
could be established.
The latest and most striking results of these experiments and the subsequent theoretical interpretation
demanding our current attention in the next beam-times, is the investigation of a novel de-excitation
mechanism revealed by our research. This relates to the fast re-emission of alpha-like fragments, after
very few nuclear interactions. This process has been found to be distinct from break-up and also preequilibrium emission. Following the incomplete fusion of an  particle or two loosely bound ,s in
the form of a 8Be, the re-emission of a fusing  particle with a large fraction of its initial energy, is
very important. In fact the probability of this phenomenon is even greater than that observed in 
particle induced reactions since these incomplete fusion processes occur in a low density, peripheral
region of the target nucleus. Consequently, as these incomplete fusion processes become more
important with increasing projectile energy, we find with increasing 12C energy an increasingly high
number of low energy equilibrated nuclei with mass and charge close to that of the target. Their
further decay via evaporation leads to the dominant formation of near target nuclei.
Following the success of these earlier measurements, subsequent experiments have been proposed to
and enthusiastically received by the Physics Advisory Comittee (PAC) of the National Accelerator
Centre. These proposals included the measurement of  particles emitted in the interaction of 12C
with 93Nb (PR27a) and the spectra of projectile fragments emitted in the interaction of 12C and 16O
with 93Nb (Pr32a). Each of these measurements were successfully completed and this data is currently
in the process of being analysed and compared to the theoretical interpretation. In addition to these
measurements, we have proposed setting up a new new Recoil Particle Spectrometer (RPS) facility
using silicon microstrip detectors, in order to measure 8Be inclusive spectra in the bombardment of a
93Nb target with 12C beams, detecting the unbound 8Be as two breakup  particles in coincidence.
This facility is currently in an advanced stage of preparation and we expect to begin testing in
September of 1998 followed by measurements in the early part of 1999. The work has led to many
publications and conference presentations.
Inter-disciplinary Research, Industrial Collaborations, Service Analysis using the Ion MicroBeam Facility
Staff :
AH Andeweg, JUM Beer, SH Connell, K Coone, RJ Hart, E Rood JPF Sellschop, E
Sideras-Haddad.
Students :
BP Doyle, CG Fischer, IZ Machi, RD Maclear, DB Rebuli, TG Stevens, ZZ Vilakazi
Collaborators :P Aggerholm (Aarhus) K Bharuth-Ram (UDW), JE Butler (NRL-Washington),
E Sendezera (University of Zululand), MHB Breese (SPM Unit, Oxford) G Bench
(Lawrence Livermore National Laboratory), A Antolak and D Morse (Sandia National
Laboratory).
The 6MV Tandem accelerator and the 2.5MV single ended POTCH accelerator provide the beams
which are used by the Micro-Scanning Ion Beam Analysis Facility (Figure 1). These beams can be
focused to micron or in some cases to submicron dimensions, and rastered over the sample, where
46
“fingerprint” radiation from some kind of physics phenomena is excited, labelling the elements in the
sample. The analysis is also a (trace level) quantitative microscopy. The computer acquisition system
can correlate the beam scan position and the amount of “fingerprint” radiation with pixel colour levels
in a visual image. The current quantitative microscopies available at the facility are :
-PIXE
Proton Induced X-ray Emission : Quantitative analysis and mapping of heavy
elements (Z  13) with as low as 1 ppm sensitivity. The probed volume is from surface to about 30
m. The microscopy is based on the fluorescence of atomic X-rays by the interaction of the beam
of protons or heavier projectiles on the sample.
-STIM
Scanned Transmission Ion Beam Microscopy : Quantitative 3-Dimensional
mapping of the sample density using Computed Tomographic Reconstruction. This microscopy is
based on the energy loss of beam traversing thin samples ( < 50 m)
-RBS
Rutherford Back Scattering : Quantitative analysis and mapping of elements heavier
than the matrix. Depth dependence from surface to 10 m is resolved and measurements on a
microscanning mode enable 3-D imaging. This microscopy is based on simple kinematics models
and makes use of reliable software analysis packages.
-NRA
Nuclear Reaction Analysis : Quantitative analysis and mapping of some elements
(B, F, N, O etc) down to few tens ppm levels. This microscopy is based on nuclear reactions
between the beam and selected elements in the sample.
-ERDA
Elastic Recoil Detection Analysis : 3-D quantitative analysis and mapping of very
light elements. This microscopy is based on simple kinematics and is particularly suitable for
hydrogen analyses. Current detection limits are around 100 ppm.
-Channeling in conjunction with PIXE, ERDA, NRA and RBS: This microscopy enables lattice
locations of elements to be determined, suppression of matrix element signals and evaluation of
lattice integrity. This microscopy exploits the crystalline structure of the matrix.
-SecEM
Secondary Electron Microscopy : Mapping of surface morphology. This microscopy
is based on collection and analysis of secondary electrons ejected out of the sample by the beam.
The nuclear microprobe facility is currently used in research applications which cover the fields of
geosciences, metallurgy, earth sciences, environmental studies, paleoclimatic research, biology and
biomedicine. In addition there are projects in the field of nuclear-solid state research and particularly
in studies of diamond physics. New analytical methodology has been established, which is based on
ion-solid interactions and is applied in impurity studies in diamond as well as hydrogen and oxygen
diffusion.
47
Development of Accelerator Mass Spectrometry for Ultra-trace and dating studies in
Interdisciplinary Research
Staff :
AH Andeweg, JUM Beer, SH Connell, K Coone, RJ Hart, E Rood JPF Sellschop, E
Sideras-Haddad.
Collaborators :P Aggerholm (Aarhus), T. Brown (Lawrence Livermore National Laboratory), J
Southon (Lawrence Livermore National Laboratory), S Freeman (Lawrence Livermore
National Laboratory), J Butler (Naval Research Laboratory), S Sie (CSIRO,
Australia)
Modern AMS is a new state-of-the-art technology for ultra-trace and dating studies in
interdisciplinary sciences. It is highly fundable as well as very marketable. Its target User group find
it easier to comprehend than other nuclear science based interdisciplinary technologies. In addition
the potential User group also contains large industrial concerns. Development of the WITS-Northern
Accelerator Facility to the level of AMS capability is one of the key features of a long term plan to
stabilise the funding and upgrade the performance of the Tandem Accelerator. AMS is an
exceptionally efficient use of beam-time, and is accommodated very well along with other research
programmes on the same facility. Besides providing excellent new interdisciplinary research
opportunities, it is expected that the project will benefit all the research based at the accelerator, as it
will provide the funding to upgrade the facility and acquire further staff.
While conventional mass spectrometry techniques, such as SIMS, ICP-MS and SRIMP, and decay
counting are efficient for determining isotopic ratios as low as 10-9 in microgram to nanogram
samples, they cannot detect efficiently long-lived isotopes (mean lives from tens to million of years),
especially with isotopic ratios as low as 10-9 to 10-15. An additional problem in ultrasensitive mass
spectrometry measurements is that the rare isotope signal is very small as compared to those of
interfering atoms and molecules with very similar masses, which are impossible to be filtered out. It
is in this ultra sensitive regime with long lived radioisotopes that Accelerator Mass Spectroscopy or
briefly AMS, came to play a very important role with some unpredictable revolutionary applications,
especially in the field of biomedicine. The extracted ions, in the form of a negative beam, are
accelerated to high kinetic energies by a positive electric field of some million volts in a nuclear
electrostatic accelerator. In the centre of the accelerator, a cell containing a small volume of gas or a
thin carbon foil is located. The accelerated incoming ions undergo collisions, losing one or more
electrons and become positive ions exhibiting a range of charge states. In this way, all molecular
species dissociate and cannot interfere with the isotope of interest any more. However, atomic
isobaric interference still remain. To completely resolve these, the isotopes have their mass, energy,
velocity and charge determined by standard nuclear physics instrumentation techniques. This is
possible because of the high energy of the ion-beam. The result is an AMS instrument with a
sensitivity typically six orders of magnitude greater than that of conventional mass spectrometry
techniques.
The User base is being canvassed. Applications to external funding sources are in progress. Support
from National and International institutes is currently being negotiated. A pilot project is being
supported using outside funds. The initial design for the system is also in progress. At this stage the
response from potential users and funders, as well as the support from various national and
international institutions is very encouraging. The Vice president of the CSIR has fully supported the
planned development and has taken a leadership role in promoting it as well as forming a
development partnership whereby CSIR sample preparation facilities and recognised expertise will
form part of the final joint facility. The international community has also been extremely enthusiastic,
and more than three tons of very sophisticated equipment has been donated by various foreign AMS
48
laboratories. The combined value of this equipment, some of which has already arrived, is over $500
000.00. The CSIR have funded the shipment costs. The progress in computerisation of the current
facility is proceeding very well, and has already been discussed. The market survey and business plan
generation components are also currently underway.









A brief mention of topics to be addressed follows :
Research in Global and Regional Climate Change
Characterisation of atmospheric pollution in terms of anthropogenic activities
Characterisation of Regional Groundwater Systems
Anthropology, History and Preservation Technology
AMS in Biomedical Dosimetry
Applications of AMS in Geosciences and Isotope Geology
Ultra-Trace Elemental Analysis
Isotope-Geochronometry and Tracers
These topics have been given more detailed profile elsewhere.
Projects in (Nuclear) Geology
Staff :
RJ Hart
Students :
Collaborators :SH Connell (WITS), E SIderas-Haddad (WITS), JPF Sellschop (WITS), M Tredoux, M
de Wit (UCT), R. Hargraves and M. Cloete (Council for Geoscience) DG Pearson
(Dept of Terrestrial Magnetism, Carnegie Institution of Washington), M Cloete and M
Drury (Utrecht), D Moser (Royal Ontario Museum), E Eida (Norwegian Geological
Survey), M. Rebak (de Beers)
Sulphide Inclusions in Diamond
Proton-induced X-ray emission (micro-PIXE) and instrumental neutron activation analysis (INAA)
methods are used to obtain information about the platinum-group elements (PGE; Pt, Pd, Rh, Ru, Os,
and Ir), and sometimes Au and Re also, in microscopic sulphide inclusions from diamonds. Samples
of known paragenesis have to be selected. The research project is long term aimed at mantle PGE
chemistry as well as the genesis mechanisms of diamond.
A study of the magnetic anomaly near the centre of the Vredefort structure
Ongoing research on the Vredefort structure has been conducted by our group for many years.
Current active areas are the following :a) Transmission Electron Microscope work on the orientation of magnetic minerals in relation to
shock deformation features in quartz.
b) Atomic magnetic force analyses on magnetic thin sections in order to determine the source of
high remanence in the rocks from the Vredefort basement.
Regional geology - Investigation of the Morokweng structure
The Morokweng structure, located in the North West province of South Africa, stands out clearly on
the regional aeromagnetic map of southern Africa as a ~70 km diameter circular feature made up of
concentric magnetic anomalies. The region is almost entirely covered by post-Cretaceous Kalahari
beds, and interpretation of the subsurface stratigraphy beneath the Kalahari sands relies on the scant
outcrop, chips from geohydrological boreholes and geophysical data. The rocks beneath the Kalahari
49
cover consist largely of Archaean granites and rocks of the Kraaipan Group, composed of banded
ironstones, meta-volcanics and minor ultramafics. Away from the structure to the south and west the
crystalline basement rocks are overlain by gently dipping Proterozoic sediments. The circular
structure was initially interpreted as an igneous intrusion. However, the superficial similarity of the
aeromagnetic signature to other known impact sites and the identification of planar deformation
features (PDFs) and other shock deformation phenomena found in surface pebbles and in rocks
recovered from boreholes. has led to the reinterpretation of the feature as an impact structure.
This study includes the following.
a) Proton probe analyses of Platinum rich phases recovered from boreholes.
b) U-Pb analyses of zircons recovered from a postulated impact melt.
c) Ar-Ar analysis of biotites recovered from a postulated impact melt sheet
Origin of the quartz norite
The quartz norite is an unusual lithology in the context of regional geology of the western Kaapvaal
craton. It is more basic than the underlying basement granites, yet it contains more quartz than typical
mafic and ultramafic rocks of the Kraaipan group. Although the mineralogy and textures of the quartz
norite superficially resemble those of plutonic rocks such as silica-rich norites or rocks of charnocitic
affinity, they have concentrations of some siderophile and chalcophile elements more characteristic of
mafic or even ultramafic rocks such as basalts or peridotites. Similarly, the Ni-rich phases (e.g.
liebenburgite and the Ni-oxides) hosted by the quartz norite are exceptionally rare. The origin of the
quartz norite is uncertain however, the shape of the body (the absence of any discernible roots) the
chilled basal margin and the evidence for shock metamorphism in the basement, has led to the
conclusion that these rocks represent an impact melt sheet. Both the clear, undeformed, prismatic
zircons, and the primary biotites exhibit the morphology of minerals that crystallised from a magma.
These minerals provide indistinguishable ages using two different dating systems and we interpret
this circa 145 Ma age as the time of crystallisation of an impact melt. In view of recent speculation
that meteorite impacts could cause flood basalts and major rifting events, the late Jurassic age for the
Morokweng impact is very interesting, because this period is generally considered to be a time of
accelerated global geological activity. This is especially true in the southern hemisphere, where this
time period coincides with the break-up of the Gondwana super continent. In the context of the
dramatic geological activity at the time, it is interesting to note that the Jurassic–Cretaceous (J–K)
extinction event is listed by Raup and Sepkoski (1986) as one of the eight major episodes. The exact
nature of this extinction and its absolute age are both still a matter of keen debate:
International collaborative study on Cretaceous -Tertiary (K-T) boundary samples recovered
from the ocean floor
The objective is to analyse samples from Leg 165 from a trans-Atlantic traverse, as well as K/T
sections on land in Mexico and Belize will be analysed for ultra-low level Ir concentrations.
This is a new international collaboration on the nature of the ocean floor deposits of the CretaceousTertiary (K/T) boundary. The purpose of this project is too analyse ocean floor deposits associated
with the K/T boundary for Ir, thought to be indicative of an impact event. The section comes from a
deposit about 1500 km from the Chicxulub crater, the proposed impact site for the K-T extinction
event. The section has a well developed tectite layer, in which we found shocked quartz. There are
limestones of varying descriptions either side.
50
Accelerator Facility Equipment Inventory
1
6 MV EN-Tandem Van de Graaff accelerator with 8 beamlines
a)
Neutron activation + remote measurement facility
b)
Neutron radiography line
c)
Quantitative analytical Heavy-Ion Microprobe
d)
Nuclear-Solid State Physics TDPAD facility
e)
High Energy Heavy-Ion Implantation Facility
f)
PIXE analysis of Environmental Aerosols
g)
Pure Nuclear Physics Experiments
h)
Oxygen and Nitrogen analysis
2.
2.5 MV Van de Graaff accelerator
a)
Dual injector to the Ion-Microprobe (high resolution analytical microscopy)
3.
Off-line counting systems
a)
gamma spectroscopy
b)
positron spectroscopy
4.
Nuclear data processing instrumentation
a)
+/- 500 pulse processing modules
5.
Computerised Data Acquisition
a)
CAMAC based Physics Analysis Workstation (PAW ex CERN)
b)
OMDAQ dedicated to Microprobe projects
c)
The GeniePC Spectroscopy Suite for singles measurements
6. Tandem Peer-to-Peer LAN (Unix, OS/2, W95 lab services cluster)
a)
WWW server
b)
FTP, Program and file Server
c)
CDROM burner
d)
DAQ workstations
e)
Analysis workstations
7
Neutron Activation Analysis Facility
a)
sample preparation
b)
automated sample changer
c)
gamma spectroscopy
d)
on-line Analysis System
Accelerator Facility Status Report
1.
6 MV EN-Tandem Van de Graaff accelerator with 8 beamlines
Excellent performance with all beams. In particular, the accelerator has operated near its
design voltage with heavy-ion beams at high charge states and currents with impressive
stability, reliability and requiring very little operator intervention. This is attributed to :
a)
the husbanding of the new tubes, belt and column resistors installed a few years ago
b)
the new management culture with a unified technical vision and upgrading during
repairs and developments
c)
better vacuum practice as allowed by increased running cost allocations
d)
new skills (eg sabbatical of P Aggerholm (Denmark) and acquisition of E Rood)
The beam-lines and target stations currently in use are in good working order, and
some have received major development as part of the implementation of new projects.
51
2.
3.
4.
5.
6.
7.
2.5 MV Van de Graaff accelerator
Installation as dual injector to the Ion-Microprobe for high resolution analytical microscopy is
complete. There has been both H and He beams into the chamber of impressive brightness and
stability. However operation continues to be unreliable. The HV platform electronics, vacuum
and gas supply equipment have now all been overhauled or replaced. Recent air tests are now
delivering reliable operation, and tests under pressure are in progress. The EN-Tandem has
had to carry all the Ion-Microprobe projects during this period, and this has been very
strenuous. However, we have every expectation that the “Potch” machine will soon be
operational. It is supposed to have a legendary reliability and require very low overheads in its
operation. It is intended to be deployed for the routine proton-Microprobe work at very high
spatial resolutions and rapid turn-around times.
Off-line counting systems
These are state-of the art systems and in good operating order and regularly used.
Accreditation by the CNS for IGP purposes is in progress.
Nuclear data processing instrumentation
These are state-of the art systems and in good operating order and regularly used.
Computerised Data Acquisition
These are state-of-the-art systems and in good operating order and regularly used. The
COLLECT DAQ system is an innovation, discussed above.
Tandem Peer-to-Peer LAN (Unix, OS/2, W95 lab services cluster)
Most of the facilities still represent high-end computers, due to the upgrade following the theft
of 11 computers from the laboratory in early 1996. In some cases finances for further upgrades
have been applied for.
Neutron Activation Analysis Facility
As part of the restructuring of the Schonland, the NAA facility was recently relocated to the
old Neutrino Surface Station Laboratory. This has resulted in a cleaner and redesigned
installation, in a very low background environment. The DAQ software server is currently
being upgraded. This system is in continual use.
52
Post Acceleration Stripper
6 MV EN Tandem Accelerator
Analysing Magnet
Analyser slits
Object
Slits
Switcher Magnet
90 degree
bending magnet
Object Slits
Quadrupole
doublet
Analyser
slits
Cooled
protection
slits
Optical / CCD
Object slits
RBS Detector
2.5 MV
Van de Graaff
Accelerator
Backscattered
beam
RBS
6.8 m
Ion Beam
Focussing
Microbeam
quadrupole
1-10 m
magnets
ERDA Detector
Forward
scattered
light ions
Transmitted H.I.
beam
Nuclear reaction
products
X Rays
Pneumatic
valve
Collimator slits
Secondary
electron
emission (SEM)
PIXE Detector
Microprobe
end station
NRA Detector
SEM Detector
Schematic representation of the Accelerator Laboratory, showing mainly the Ion-Microprobe Facility.
The inset is a schematic diagram of the focused ion-beam exciting radiation from a sample, leading to
various (trace) quantitative microscopies. The other 7 available beamlines are shown schematically
and truncated.
53
Usage of the Accelerator Laboratory (1997-1998 2-year average)
Project
Group
Proposers
Percentage
Many projects under the
programme:
Particle-Solid Interactions
SH Connell, BP Doyle, IZ Machi, RD
Maclear JPF Selschop E Sideras-Haddad all
WITS-Physics
25%
ERDA for H in Diamond
JE Butler NRL-Washington
Many projects under the
programme:
Environmental Aerosols
PIXE analysis of time
dependent aerosol streaker
samples
Many projects using the IonMicroprobe
HJ Annegarn, SJ Piketh, S Meter, P
Formenti
20%
WITS-Physics, WITS Climatology
Council for Geosciences
D De Bruyn
Atomic Energy Corporation
M Andreoli
20%
BOART hard materials
SA Inst of Med. Res.
S Luyckx : WITS-Metallurgy
Anglo American Res Labs
S Lee
Inst Mineralogie - Hannover
C Smith
Development, Calibration
A Wittenberg
SH Connell, E Sideras-Haddad
Neutron Radiagraphy
Applied Neutron Physics
JIW Watterson WITS-Physics
5%
Neutron Activation
Applied Neutron Physics
JIW Watterson WITS-Physics
5%
Many projects under the
programme:
Lattice effects in II damage
propagation
CG Fischer WITS-Physics
5%
High Energy Heavy-Ion
Implantation
HEHI in Semi-conductors
S Goodman : UPretoria-Physics
HEHI in Alkali Halides
A Davidson : UZululand-Physics
HEHI in thin films
M Maaza : WITS-Physics
Thin Diamond production
JPF Sellschop : WITS-Physics
Scheduled maintenance
AH Andeweg, JUM Beer, E Rood
Unscheduled
10%
10%
54
SchonLAN Computer facilities
LAN Supervisor :
BP Doyle
LAN Assistant Supervisor : RD Maclear
Computer Representative : SH Connell
Electronics :
AH Andeweg, K Cooney
The computer facilities at the SRCNS can be divided into two major sections: the SchonLAN Novell
server and the workstations which connect to it, and the UNIX network. There are also a few off-line
PCs (mainly used for data acquisition).
The SchonLAN Novell Network
The SchonLAN network runs under Novell 4.11 and has about 75 users. The majority of people at the
SRCNS use this network for their printing, applications and e-mail needs. The server itself is a
Pentium 100 with 64MB RAM, 5GB of hard drive space, a DAT 2 tape drive and a CD-ROM (all
SCSI). The physical cabling system is 10MB 10 Base-T. This machine is also a file server for shared
data and certain applications (MS-Office, user ed applications etc.).
UNIX (LINUX) Network
Over the last few years there has been a rapid development of a UNIX network at the SRCNS. This
has mainly been due to the powerful data acquisition and manipulation software that has become
available. The network consists of 8 PCs running Linux. This network utilises the same cabling
system as the SchonLAN. This network hosts the WWW servers, FTP servers, amongst other
specialised servers for Unix environments.
55
Publications (1998-99)
1) DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm,
JE Butler, JPF Sellschop
Oxygen surface studies in ultra-thin diamonds using transmission channeled Rutherford
Forward Scattering
Nucl. Instr. & Meth. in Phys. Res. 158 (1999), 701-705
2) RJ Sweeney, VM Prozesky, KS Viljoen and SH Connell
The sensitive determination of H in diamond by infrared (FTIR) spectroscopy and
micro-elastic-recoil (m-ERDA) techniques
Nucl. Instr. & Meth. in Phys. Res. 158 (1999), 582-587
3) E Sideras-Haddad, SH Connell, JPF Sellschop, R Hart and M Tredoux
Anomalous Fe and Mn heterogeneity observed in microscopic inclusions in diamond
using nuclear microscopy
Nucl. Instr. & Meth. in Phys. Res. 158 (1999) 612-615
4) SJ Piketh, E Sideras-Haddad, K Holmgren, PD Tyson
Proton micro-probe analysis of a stalagmite from South Africa
Nucl. Instr. & Meth. in Phys. Res. 158 (1999) 606-611
5) RD Maclear, JE Butler, SH Connell, BP Doyle, IZ Machi, DB Rebuli, JPF Sellschop, E
Sideras-Haddad
The distribution of hydrogen in polycrystalline CVD diamond
Diamond and Related Materials 8 (1999) 1615-1619
6) DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF Sellschop
Oxygen on Diamond Surfaces
Diamond and Related Materials 8 (1999) 1620-1622
7) IZ Machi, JE Butler, SH Connell, BP Doyle, RD Maclear, JPF Sellschop, E Sideras-Haddad,
and D Rebuli
Diffusion Characteristics of Hydrogen in Diamond
Diamond and Related Materials 8 (1999) 1611-1614
8) CG Fischer, SH Connell, PG Coleman, W Anwand, G Brauer, F Malik, JPF Sellschop
A slow positron beam investigation of positron-defect interaction in single crystalline
synthetic type IB diamonds and a natural type IIB diamond
Applied Surface Science (1999)
9) IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear,
BP Doyle, JE Butler, R Scheuermann and A Seeger.
Muonium studies of p-type semi-conducting diamond under conditions of UV-visible
illumination
Hyp. Int. 120/121 (1999) 585-589
10) JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt,
P Murphy, RWN Nilen, and JPF Sellschop
56
Longitudinal Field - Muon Spin Relaxation (LF-mSR) measurements and evidence for a
new muonium defect site in type Ia diamond
Hyp. Int. 120/121 (1999) 579-583
11) M.G. Bossenger, S.H. Connell, E. Sideras-Haddad, H. Appel, B.P. Doyle, W. Verwoerd, K.
Bharuth-Ram, J.P.F. Sellschop, C.G. Fischer and V. Nolting
Site occupancy and molecular complex formation of 19F ions in fullerenes C60 and C70
studied by TDPAD
Hyp. Int. 120/121 (1999) 557-562
12) K Kirsebom, YuV Kononets, U Mikkelsen, SP Møller, KT Nielsen, E Uggerhøj, T Worm, K
Elsener, C Biino, S Ballestrero, P Sona, SH Connell, JPF Sellschop, ZZ Vilakazi.
Enhanced electromagnetic showers initiated by 20-180 GeV gamma-rays on aligned
thick germanium crystals.
Nucl Instr. & Meth. in Phys. Res. B (1999) 472-478
13) K Kirsebom, YuV Kononets, U Mikkelsen, SP Møller, E Uggerhøj, T Worm, K Elsener, C
Biino, S Ballestrero, P Sona, RO Avakian, K Ispirian, SP Taroian, SH Connell, JPF Sellschop
and ZZ Vilakazi.
Generation and detection of the polarisation of multi-GeV photons by use of two
diamond crystals
Phys. Lett B 135 (1998) 347-353
14) E Gadioli, M Cavinato, E Fabrici, E Gadioli Erba, C Birattari, I Mica, S Solia TG Stevens, SH
Connell, JPF Sellschop, GF Steyn, SV Förtsch, JJ Lawrie, FM Nortier and AA Cowley.
Alpha particle emission in the interaction of 400 Mev 12C with 59Co and 93Nb
Proceedings of the The Nucleus: New Physics for the New Millennium Faure, South Africa,
18 - 22 January 1999 by Plenum Publishing Corporation
15) E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, V Allori, G Bello, F Cerutti, A
di Filippo, TG Stevens, SH Connell, JPF Sellschop, FM Nortier, GF Steyn, C Marchetta
The Interaction of 12C and 16O with 103Rh
Heavy Ion Physics 7 (1998) 275 - 287
16) E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, V Allori, G Bello, F Cerutti, A
DI Filippo, S Vailati, TG Stevens, SH Connell, JPF Sellschop, FM Nortier, GF Steyn, C
Marchetta
Angular Distributions and Forward Recoil Range Distributions of Residues Created in
the Interaction of 12C and 16O with 103Rh
Nucl Phys A 641 (1998) 271
17) E Gadioli, M Cavinato, E Fabrici, E Gadioli Erba, C Birattari, TG Stevens, SH Connell, JPF
Sellschop, FM Nortier, GF Steyn
Thermalization of the Intermediate Nuclei in Fusion and Incomplete Fusion Reactions
Proceedings of the Predeal School on Structure and Stability of Nucleon and Nuclear Systems
1998 World Scientific
57
18) SH Connell, JPF Sellschop, JE Butler, RD Maclear, BP Doyle, IZ Machi
A study of the mobility and trapping of minor hydrogen concentrations in diamond in
three dimensions using quantitative ERDA microscopy
Diamond and Related Materials, 7 (1998) 1714 - 1718
19) RD Maclear, SH Connell, BP Doyle, IZ Machi, JE Butler, JPF Sellschop, SR Naidoo, E
Fritsch
Quantitative trace hydrogen distributions in natural and synthetic diamond using 3Dmicro-erda microscopy
Nucl Instr and Meth in Phys. Res B 136-8 (1998) 579 - 582
20) K Kirsebom, U Kononets, U Mikkelsen, SP Moller, E Uggerhoj, T Worm, C Biino K Elsener,
S Ballestrero, P Sona, SH Connell, JPF Sellschop, ZZ Vilakazi, A Apyan, RO Avakian, K
Ispirian.
Pair production by 5-150 GeV Photons in the strong crystalline fields of germanium,
tungsten and iridium
Nucl Instr. & Meth. in Phys. Res. B 135 (1998) 143-148
21) B.P. Doyle, J.K Dewhurst, J.E. Lowther and K. Bharuth-Ram
Lattice locations of indium implanted in diamond
Phys. Rev. B, 57 (1998) 4965-4967.
22) KL Bhatia, S Fabian, S Kalbitzer, Ch Klatt, W Kratschmer, R Stoll and JPF Sellschop
Optical effects in carbon-ion irradiated diamond.
Thin Solid Films 324 (1998) 11-18
23) JPF Sellschop
Production of diamond single crystals for synchrotron X-ray beamlines
Proc of SPIE 3448 (1998) 40 - 52 in Crystal and Multilayer Optics Editors: Albert T
Macrander, Andreas K Freund, Tetsuya Ishikawa, Dennis M Mills
24) AK Freund, JPF Sellschop, K Lieb, S Rony, C Schulze, L Schroeder, J Teyssier
Recent diamond single crystal X-ray optics developments at the European Synchrotron
Radiation Facility
Proceedings of SPIE 3448 (1998) 53 - 63 in Crystal and Multilayer Optics Editors: Albert T
Macrander, Andreas K Freund, Tetsuya Ishikawa, Dennis M Mills
25) JPF Sellschop, P Kienle
Method of making carbon with electrically active sites
Provisional patent, #98/2242, filed on 17 March 1998
26) JPF Sellschop
A method of altering the colour of a material
Provisional patent, #98/5495, filed on 24 June 1998
27) JPF Sellschop
Method of producing n-type doped carbon
Provisional patent, #98/8792, filed on 25 September 1998
58
28) JPF Sellschop
Isotope conversion
Provisional patent, #98/10414, field on 13 November 1998
29) JPF Sellschop
pn, junctions
Provisional patent, #98/10413, filed on 13 November 1998
30) M. A. G. Andreoli, L.D. Ashwal, R. J. Hart, and J. M. Huizenga.
Petrology and Geochemistry of nickel, iridium-rich quartz norite from the late Jurassic
Morokweng impact structure, South Africa.
Special publications of the Geological Society of America 339 (1999) 1-18.
31) Marian Tredoux, Rodger J. Hart, Richard W. Carlson, Steven R. Shirey
Ultramafic rocks at the centre the Vredefort structure: further evidence for the crust-onedge model.
Geology 27 (1999) 923-926
32) R. J. Hart, D Moser, M. A. G. Andreoli.
Archaen granulite facies rocks near the centre the Vredefort structure, South Africa:
Implications for the evolution of the Kaapvaal craton.
Geology 27 (1999) 1091-1094.
33) Marthinus Cloete, Rodger J Hart, Herbert K Schmid, Martyn Drury, Chris M. Demanet, K.
Vijaya Sankar.
Characterization of magnetite particles in shocked quartz by means of electron- and
magnetic force microscopy : Vredefort, South Africa
Contributions to Mineralogy and Petrology 137 (1999) 232-245
34) T Mauro, G Bench, E Sideras-Haddad, K Feingold, P Elias and C Cullander
Acute Barrier Pertubation Abolishes the Ca and K Gradients in Murine Epidermis:
Quantitative measurements Using PIXE.
The Journal of Investigative Dermatology, Vol. 111, No 6 (1998) 1198-1201
59
Conferences and Visits (1998)
International Conferences 1998
International Workshop on Radiation Physics with Relativistic Electrons, Tabarz, Germany 9
- 12 June 1998
JPF Sellschop (Invited)
The production of thin and thick diamond targets for energetic electron and synchrotron
radiation studies
1. ZZ Vilakazi, SH Connell, JPF Sellschop, U Mikkelsen, U Kononets, K Kirsebom, SP Moller, E
Uggerhoj, T Worm, K Elsener, S Ballestrero, P Sona, C Biino, R Moore, RO Avakian, K Ispirian,
A Apyan
Investigation of pair production and its dependence on correlated effects when multi-GeV
photons are incident on Ge crystal
International Conference on Hyperfine Interactions, Durban August (1998)
1
Doyle, E.J. Storbeck, U. Wahl, S.H. Connell and J.P.F. Sellschop
Study of indium-defect interactions in diamond using 2-D CEEC
2
Storbeck, U. Wahl, B.P. Doyle, S.H. Connell and J.P.F. Sellschop
A 2-D CEEC study of the second configuration observed for indium implanted into pure diamond
3
JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt,
RWN Nilen, and JPF Sellschop
Longitudinal Field - Muon Spin Relaxation (LF-mSR) measurements in type Ia diamond
4
IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear, BP
Doyl1, JE Butler, R Scheuermann, and A Seeger
Muonium studies of p-type semi-conducting diamond under conditions of UV-visible illumination
5
SH Connell, IZ Machi, CG Smallman, JPF Sellschop, K Bharuth-Ram, RWN Nilen, J Major, R
Scheuermann, and A Seeger
Possible observation of quantum diffusion of MuT in diamond
6
M.G. Bossenger, S.H. Connell, E. Sideras-Haddad, H. Appel, B.P. Doyle, W. Verwoerd, K.
Bharuth-Ram, J.P.F. Sellschop, C.G. Fischer and V. Nolting
Site occupancy and molecular complex formation of 19F ions in fullerenes C60 and C70 studied
by TDPAD
60
International Symposium on Optical Science, Engineering, and Instrumentation : SPIE's 43rd
Annual Meeting 1998
1
JPF Sellschop
Production of diamond single crystals for synchrotron X-ray beamlines
2
AK Freund, JPF Sellschop, K Lieb, S Rony, C Schulze, L Schroeder, J Teyssier
Recent diamond single crystal X-ray optics developments at the European Synchrotron Radiation
Facility
International Conference on Nuclear Microprobe techniques and Applications, Stellenbosch, 11
- 16 October 1998
1
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JE
Butler, JPF Sellschop
Oxygen surface studies in ultra-thin diamonds using transmission channeled Rutherford Forward
Scattering
2
SH Connell, BP Doyle, IZ Machi, RD Maclear, DB Rebuli, JPF Sellschop and E Sideras-Haddad
Hydrogen chemistry and dynamics in diamond studied using 3D-ERDA microscopy
3
E Sideras-Haddad, SH Connell, JPF Sellschop, R Hart and M Tredoux
Anomalous Fe and Mn heterogeneity observed in microscopic inclusions in diamond using
nuclear microscopy
4
SJ Piketh, E Sideras-Haddad, K Holmgren, PD Tyson
Proton micro-probe analysis of a stalagmite from South Africa
International Conference on New Diamond Science and technology, Pretoria, 31 August - 2nd
September 1998
1
RD Maclear, JE Butler, SH Connell, BP Doyle, IZ Machi, DB Rebuli, JPF Sellschop, E SiderasHaddad
The distribution of hydrogen in polycrystalline CVD diamond
2
DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF Sellschop
Oxygen On Diamond Surfaces
2
IZ Machi, JE Butler, SH Connell, BP Doyle, RD Maclear, JPF Sellschop, E. Sideras-Haddad, and
D. Rebuli
Diffusion Characteristics of Hydrogen in Diamond
61
Eighth International Workshop on Slow Positron Beam Techniques for Solids and Surface,
SLOPOS - 8, Cape Town, 6 - 12 September 1998
1
CG Fischer, SH Connell, PG Coleman, W Anwand, G Brauer, F Malik, JPF Sellschop
A slow positron beam investigation of positron-defect interaction in single crystalline synthetic
type IB diamonds and a natural type IIB diamond
2
CG Fischer, SH Connell, PG Coleman, F Malik, JPF Sellschop
A slow positron beam depth profiling of single crystalline natural type IIA, type IIB and synthetic
type IB diamonds
Abstract in Proceedings of 17th general meeting of the International mineralogical association.
Toronto, Canada, August 1998
1
Cloete M, Hart R, Schmid H, Demanet C, Sankar V, Mar? L and Drury M.
Crystallographic and magnetic orientations of magnetite particles in shocked quartz, Vredefort,
South Africa.
Symposium on Witwatersrand and Vredefort Metamorphism and Mineralization, Cape Town
February 1998
1
Rodger Hart, Marco Andreoli, Desmond Moser and Marian Tredoux.
Bushveld beneath the Vredefort structure: fact or fiction?
Impacts and the early Earth workshop, Cambridge, 1998
1
Iain McDonald , Rodger J. Hart , Marco A.G. Andreoli , and Marian Tredoux.
Platinum-Group Element Geochemistry Of The Quartz Norite Impact Melt From The Morokweng
Structure, Southern Africa: Clues To The Type Of Impactor.
The 62 nd Annual Meteoritical Society Meeting Johannesburg, 11th to 16th July 1999.
1
R.J. Hart and M. Cloete
Impact related magnetic rocks from the vredefort impact structure
Diamond Conference, London, England, July 1998
1.
B Doyle, R Maclear, JPF Sellschop, SH Connell, E Sideras-Haddad and JE Butler
Where is the hydrogen in CVD diamond?
2.
JM Baker, IZ Machi, SH Connell, K Bharuth-Ram , JE Butler, SFJ Cox, CG Fischer, T Jestadt,
RWN Nilen and JPF Sellschop
Longitudinal field muon spin relaxation (LF-SR) measurements in type IA diamond
3. E Sideras-Haddad, D Rebuli, SH Connell, JPF Sellschop, B Doyle and R Maclear
Oxygen on diamond
62
4. IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, R Maclear, BP
Doyle, JE Butler, R Sheuerman and A Seeger
Study of diamond and its defects using transverse field muon spin rotation (TF-SR)
5. CG Fischer, SH Connell and JPF Sellschop
Near surface to bulk characterisation of diamond by positron annihilation
6. JPF Sellschop, A Freund, W Greiner and M Rebak
On the bending of diamond
7. SH Connell, IZ Machi, CG Smallmann, JPF Sellschop, K Bharuth-Ram, RWN Nilen , J Major, R
Scheuerman and A Seeger
Quantum diffusion of the interstitial muonium (MuT) in diamonds with induced vacancies
8. E Storbeck, B Doyle, SH Connell, JPF Sellschop and U Wahl
Lattice location studies of In-111 in diamond using the Isolde facility at CERN
9. JM Baker, P Murphy, IZ Machi, SH Connell, K Bharuth-Ram, SFJ Cox, JE Butler, CG Fischer, T
Jestadt, RWN Nilen and JPF Sellschop
Muonium at a site of rhombic symmetry in type Ia diamond
Local Conferences
SAIP Conf, UCT, 8-10 July 1998
1. Maclear, S.H. Connell, M. Hogan, A.H. Andeweg, J.P.F. Sellschop and F. Weehuizen,
The Schonland Research Centre EN-Tandem Accelerator Control System,
South African Institute of Physics Conference, Cape Town, 8-10 July, 1998
2. Doyle, S.H. Connell, J.P.F. Sellschop and U. Wahl,
PAC study of indium-defect interactions in diamond
3. Doyle, E.J. Storbeck, U. Wahl, S.H. Connell and J.P.F. Sellschop,
Study of indium-defect interactions in diamond using 2-D CEEC
4. Storbeck, U. Wahl, B.P. Doyle, S.H. Connell and J.P.F. Sellschop.
A 2-D CEEC study of the second configuration observed for indium implanted into pure
diamond
5. Doyle, J.E. Butler, S.H. Connell, I.Z. Machi , R.D. Maclear, J.P.F. Sellschop and E. SiderasHaddad,
Diffusion Characteristics of Hydrogen in CVD Diamond
6. Sideras-Haddad, S.H. Connell, J.P.F. Sellschop, R. Hart and M.Tredoux,
Anomalous Fe and Mn zoning observed in microscopic inclusions in diamond using nuclear
microscopy
63
7. JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt,
RWN Nilen, and JPF Sellschop,
Longitudinal Field - Muon Spin Relaxation (LF-SR) measurements in type Ia diamond
8. IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear, BP
Doyle, JE Butler, R Scheuermann, and A Seeger,
Muonium studies of p-type semi-conducting diamond under conditions of UV-visible
illumination
9. R.D.Maclear, S.H. Connell, E. Sideras-Haddad, D.B. Rebuli, B.P. Doyle, I.Z. Machi, J.E. Butler,
P. Aggerholm and J.P.F. Sellschop,
Channeling studies of ultra-thin diamond films
10. E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, E Allori,V Ceruti, A Di Filippo, E
Galbiati, TG Stevens, SH Connell, JPF Sellschop, Sj Mills, FM Nortier, GF Steyn, C Marchetta
A comprehensive study of the interaction of 12C with 103Rh up to 33 MeV/nucleon
64
Visits of Staff and students to International Institutions
Conferences Attended and Institutions visited 1998
Date
Institution
Country
March (1 week)
INFN - Florence
Italy
ZZ Vilakazi
SH Connell
May (1week)
PSI-Zurich
Switzerland
IZ Machi
June (1 week)
Tabarz
Germany
ZZ Vilakazi
JPF Sellschop
June (1.5 months)
Uni-Bristol
England and
CG Fischer
Uni-East Anglia
Germany
Rossendorf
June/July (2 weeks)
ICTP Trieste
Italy
BP Doyle
Purpose
NA43 collaborators'
meeting
Expt Evaluation
Committee Meeting
International
Workshop Rad. Phys. with rel. eWorking visits on
ACAR and SlowPos
Spectroscopy
Electronic Structure
Calculations Workshop
and Hyperfine
Interactions conference
SPIE's 43rd Annual
Meeting 1998
July (1week)
JPF Sellschop
San Diego
USA
July (1week)
JPF Sellschop
London
UK
Diamond Conference
August (1week)
SH Connell, E SiderasHaddad + 2 students
August (1week)
SH Connell, E SiderasHaddad + 2 students
September (1week)
SH Connell, E SiderasHaddad + 2 students
September (1week)
1 student
Feb/March and
Sept/October
(5 Weeks)
SH Connell, JPF
Sellschop, E SiderasHaddad
July (1 week)
SH Connell, E SiderasHaddad
5 students
August (1 week)
Durban
RSA
Hyperfine Interactions
Conference
Pretoria
RSA
Stellenbosch
RSA
New Diamond Science
and Technology
Conference
Nuclear Microprobe
Conference
Cape Town
RSA
National
Accelerator
Centre, Faure
RSA
UCT, Cape Town
RSA
SA Inst of Physics
national conference
Toronto
Canada
17th general meeting
65
Slow Positrons
Conference
Working visits
RJ Hart
Sept (1 week)
RJ Hart
Cambridge
UK
66
of the International
mineralogical
association
Impacts and the early
Earth workshop
Visiting Scientists to WITS
Sabbatical Visits
1 Mr P Aggerholm
(Senior Technician : Institute for Physics and Astronomy, University of Aarhus, Denmark)
One year sabbatical, starting January 1998.
2 Prof EJ Sendezera
(Professor : Physics Department, University of Zululand)
(One year sabbattical starting August 1997)
Working Visits
1 Prof. E gadioli, Prof C C Birattari and student(s)
(INFN-Milano) Two working vists per year of three weeks each in February and September
Short Vists
1 Dr Marc Caffee
CAMS (Centre for Accelerator Mass Spectrometry) at Lawrence Livermore National Lab, USA.
Two days, January 1998
2 Dr. Soye Sie
Director of the HIAF (Heavy Ion Analytical Facility) at CSIRO, Sydney- Australi
Three days, September 1998
3 Dr. Mark Roberts
Facility manager of CAMS (Centre for Accelerator Mass Spectrometry) at Lawrence Livermore
National Lab, USA
Three days, September 1998
4 Prof HH Andersen
Phys Dept, Aarhus University and Editor of Nucl instr & Methods B
One day, October 1998
5 Dr Rokita
Polish Institute of Nuclear Sciences
One day, October 1998
6 Prof B Asman Phys Dept Uppsala university
One week, November 1998
Postgraduate Students
Students (graduated in 1998)
Name
Supervisor
R Nilen
SH Connell,
(MSc,PhDJPF
WITS)
Sellschop
Z Vilakazi
(PhD-WITS)
Jul 1994 -
SH Connell,
JPF
Sellschop
Jan
1994Sept
1998
Jul 1994
Sept
1998
Thesis title, progress and awards
Positron Spectroscopy in Diamond
Currently a Post Doc at the SRCNS under
JPF Sellschop
Won 3 best PhD oral presentation prizes at
the SAIP, 3rd best student oral at ICPA in
Kansas 1997
Radiation from Multi-Hundred GeV electrons
and positrons incident on Crystals
Currently a Post Doc at CERN and Lecturer
at UCT
67
Best PhD presetnation at SAIP-98 in Nuclear
and Particle physics section
Students not yet graduated by 1999
Name
Supervisos
Thesis Title
E Storbeck
Study of wide-band
MSc,PhD SH Connell, gap semi-conductors,
WITS)
JPF
specifically diamond,
Jan 1991 Sellschop
through emission
(PT)
electron channeling.
T Stevens
SH Connell, Nuclear reaction
(MSc, PhD JPF
mechanisms by
(WITS)
Sellschop
stacked foil
Jan 1993 techniques
(PT)
B Doyle
(MSc, PhDWITS)
1995 - (FT)
I. Z. Machi
(PhD - WITS)
1995 - (FT)
R.D. Maclear
(MSc, PhD WITS)
(FT)
C.G. Fischer
(MSc, PhD WITS)
(FT)
SH Connell, Impurity reactions in
JPF
diamond
Sellschop
AU Naran
(MSc - WITS)
Jun 99 D B Rebuli
(PhD - WITS)
July 1999 (FT)
B Flowers
PhD
E SiderasHadad
SH Connell
E SiderasHadad
SH Connell
Ion Beam Interactions
in Thin Diamond
Films
Accelerator Mass
Specrometry
RJ Hart
Impact structures
Status, progress and awards
Thesis submitted
Employed at SAMES for one
year, One year at the Rochester
Inst of Technology, now in
Information Technology.
Completed expt work, analysis
+ interptretation. Well
advanced with 1st draft of
Thesis. Employed at the AEC
MLIS program until its closure
(one year). Now in the IT
industry
Submitted. Now on a post-doc
at the ESRF
SH Connell, Hydrogen and
K. Bharuth Muonium in diamond
- Ram
SH Connell,
JPF
Sellschop
Submitted. Now on the staff of
UNISA Physics Dept
SH Connell,
DJ Britton
Excellent progress,
Experimental work complete.
Analysis + write-up in progress.
Has studied Financial Maths
concurrently with Physics.
Just begun
68
Excellent progress,
Experimental work almost
complete. Writing.
Just begun
HEALTH PHYSICS SERVICE
1st January 1998 to 31st December 1998
69
Introduction
The Health Physics Service was established by the University to ensure that all materials and
machines that produce radiation, are used and disposed of safely by both staff members and students
of the University. This is to safeguard both personnel and environment from the harmful effects the
uncontrolled use of radiation, may give rise to.
In this country various acts were enacted to control the use of radioactive material. In particular, the
Hazardous Substances Act sets out the regulations that deals with the acquiring, use, transport and
eventual disposal of radioactive materials and electronic products which produce radiation, be it
ionising or non-ionising radiation. The vested control lies with the Department of Health. The Council
for Nuclear Safety on the other hand, is the regulatory commission for the use of nuclear material.
The regulations for the use of such material are covered by the Nuclear energy Act.
Thus in addition to the statutory obligation, the Service has a general duty of care. This mandate
extends beyond the Main Campus to encompass the Medical School as well as part of the Chris Hani
Baragwanath Hospital.
On the University campuses the prominent sources of ionising radiation can be grouped into two. The
one group consists of machines that produce radiation and the other group consists of radioactive
material that emits radiation. The latter may in turn be divided into what are known as sealed or
unsealed sources of radiation.
Of the number of machines that produce ionising radiation, the University currently has in its
possession five accelerators, thirty-one X-ray machines, and seven electron microscopes on its
Campuses.
It has two hundred and eighty sealed sources, of that, two, because of its strength (radioactivity), are
housed in, what is generally referred to as, irradiation facilities that require major biological shielding
and safety interlocks. One of these is located at the Medical School and the other at the Schonland
Research Centre.
In addition to the above mentioned sources of radiation, the University has a number of researchers
who make use of the nuclear reactor facility that is situated at the Pelindaba site, for their neutron
activation studies. This usage often results in a wide range of neutron-activated radioisotopes being
produced in samples that are then brought onto the University campus for analysis.
Such varied activities currently engaged in by both our staff and student researchers, may subject
them to distinct risks of exposures to such different types of radiation as alpha, beta, gamma and
neutron radiation. This is especially true if adequate work procedures and precautions are not insisted
upon.
The Service has therefore the following set-ups as its function:
-
ensuring that the workplace and work procedures are designed to keep exposure to radiation as
low as possible;
-
obtaining all necessary approvals, authorisations and licences;
70
-
ensuring that doses estimated to have been received by staff and students comply with the relevant
dose limits;
-
ensuring that the doses estimated to have been received by members of the public from the
operation comply with the public dose limits;
-
developing a plan for dealing with incidents and accidents involving exposure to radiation;
-
providing consultation for staff and students who may be exposed to radiation in the course of
their work;
-
keeping records of radiation exposure resulting from the operation;
-
providing copies of dose records to staff and students on request;
-
developing and implementing a plan for monitoring exposure to radiation and for estimating doses
received by those exposed;
-
controlling the purchase and use of radiation producing materials and machines by staff and
students; and
-
ensuring that all radiation producing materials and machines are disposed of safely and in
accordance with local and international standards and recommendations.
In addition to the controlling functions mentioned above, the Service provides a personnel-monitoring
service, a decontamination service and a waste disposal service on a routine basis to the University
community. The Service runs an in-house service for the checking of radiation monitors used by the
various departments and as well offers on short term loan, health physics instrumentation to both staff
and post-graduate students involved with radiation work. Its advice to users of the Service on
instrumentation, materials and experimental procedures covers both technical and scientific aspects.
Also, of the two cobalt irradiation facilities it oversees, the Service maintains and runs the Schonlandbased facility.
Besides the “routine” aspects mentioned above, the Service undertakes a limited amount of research
and teaching. It is felt that such activities are necessary in order to maintain a service that is
professional to both staff and students of the University.
The teaching covers aspects of health physics and the research covers areas of radiation and health
physics.
Staff
The Service has the following staff complement:
Dr T.L. Nam
Director
Radiation Protection Officer / Responsible
Person (In terms of the Statues)
71
Prof. R.J. Keddy
Honorary Consultant
Acting Radiation Protection Officer / Alternate
Responsible Person (In terms of the Statues)
Mr. J. Geyer
Senior Technician
Mr. Geyer is currently the senior technician at the Service. He replaces Mr. Ramerafe who resigned
after being with the Service for just over two years.
Staff Training
To facilitate effective integration into the Service, Mr. Geyer has been allotted such tasks as the
setting up and testing of the recently acquired health-physics instrumentation. These are instruments
donated by the International Atomic Energy Agency (IAEA) to the University for the training of postgraduate students in radiation protection.
Radioactive Waste
The Health Physics Service continues to provide user departments with a waste disposal service. To
reduce costs, the Service currently makes use of departmental assistance for the loading of containers
onto transport-vehicle whenever possible. For the bulk collection of waste that are stored at
Schonland Research Centre and are awaiting bulk delivery to the Pelindaba disposal site of the
Atomic Energy Corporation(AEC), the Service has for the past year and a half, commissioned the
Service of the AEC for the task.
This policy has shown to be not only flexible and but cost effective. It has also alleviated the past
problem concerning the availability of manpower to assist in the loading and off loading of waste
drums. Furthermore, it has the added advantage of reducing the risk of accidents/incidents involving
the transport of radioactive material over longer distances.
As was reported previously, the Service continues to make use only of vehicles fitted with a tracker
system for the transport of radioactive material.
General
As in the previous year, it can again, be reported that no incident of friction involving staff members
or students and the Service has occurred over the past year. The Service has on the whole received
full co-operation from the University community in the pursuit of its functions.
Nuclear Non-proliferation Inspection
Two members of the International Atomic Energy Agency’s (IAEA) safeguards team together with a
member from the Atomic Energy Corporation conducted an inventory of depleted uranium on the
University campus. This forms part of their annual inventory-verification of nuclear material in the
country. I am pleased to report that in their submission, the inspectors expressed satisfaction over the
University’s control and use of such materials.
72
Teaching
As in previous years the Service continued to partake in formal courses offered by the Department of
Medical Physics and Department of Physics at Honours level on aspects of Radiation Protection to
students that chose Medical Physics as a topic.
Research
The research component of the Service centred on aspects of radiation physics. It is a collaborative
effort carried out jointly with members of the Department of Medical Physics and the Health Physics
Service. In the past year, the research effort of the group was directed mainly at the identification of
the parameters and the physical processes that are important for solid materials to perform effectively
as detectors of various types of radiation.
Non-University users of the Service
As in previous years the Service had during the course of the year received numerous queries from
school pupils and members of the general public on matters pertaining to radiation and the hazards
arising from its use. Where possible reference material were provided on request.
It can be reported that during the same period, a number of outside organisations also made use of the
Health Physics Service.
The Post-graduate Course Radiation Protection
More than three years ago the International Atomic Energy Agency (IAEA), and the South African
Council for Nuclear Safety approached the University through the Schonland Research Centre with
the view to establishing a post- graduate course in radiation protection. The main objective of the
IAEA is to establish regional training centres for the post graduate course at leading educational
institutions of selected member countries.
It was proposed that this University would serve as a training centre for the entire African region, that
the courses would be integrated into the curricula of the University and that the first training course
would begin in 1999.
The Agency would in turn undertake to assist by
(1) providing grants for capital equipment needed for training. This amounts to well over a million
rand over a two year period.
(2) providing consultants and lecturers to assist with establishing and conducting the course.
(3) providing grants and bursaries for foreign students.
Following this, the Schonland Centre and the Physics Department approached the Service to assist in
the development of this initiative.
In view of the following possible implications such a course will have:
(1) for the University in terms of income, if ran properly;
73
(2) for the Service in terms of equipment available;
(3) for the University in terms of possible increase in the number of masters and post-masters
students;
(4) for members of the Service in terms of professional contacts with both local and international
practitioners in the field of radiation protection;
(5) for the Service to both enhance and contribute the professional and academic expertise it has
accumulated over many years, it was felt that the Service should and would respond within its
manpower constraints, positively to the invitation.
The Service has to date provided the following input:
(1) As the proposed course is envisaged to form part of the new initiative by the Faculty of Science to
offer a Post-Graduate Diploma in the Sciences or as part of an MSc by course work and research
report from 1998 onwards, the Service made various suggestions for changes to the rules
involving the admission requirements to the course as well those which concern the awarding of
the diploma and degree, when they were being drawn up. It can be reported that many of the
recommendations, which took into account that most of the students targeted are young
professionals, now form part of the rules for the post-graduate diploma.
(2) The Service was directly and proactively involved in choice of capital equipment that will be used
not only for postgraduate training in radiation protection, but will be made available for research
and for routine monitoring by members of the Health Physics Service and other researchers of the
University.
(2) Based on the guidelines provided by the IAEA and within the constraints of the Faculty of
Sciences’ point system, the Service, with the assistance from a member for the Council for
Nuclear Safety that was seconded to the University, drafted a proposed structures for the syllabus
for the Post-graduate Diploma in Radiation Protection.
(3) (4) Over the past year, the Service has contributed significantly to the design and supervision of
building alterations and as well as in the design and the choice of furniture and fixtures that is
needed for the training centre.
One should perhaps also mention that both the nuclear industry and legislative bodies in the country
are of the opinion that organisations should use adequately trained and experienced radiation
protection specialists in radiation controlling functions. Plans are afoot to have such personnel
accredited by an accreditation board in the foreseeable future. This of course implies that there may
be opportunities for the University to offer appropriate training courses to potential users of
radioactive material and hence extend the use of the newly established training centre at the
Schonland.
Visitation
Not only did the Service played host to participants of the radio-isotope course offered by the
Witwatersrand Technikon on their annual visitation to the Schonland Research Centre during the
year, it also provided the Technikon with portable radiation monitoring equipment and radio-active
sources on loan, for the duration of the course.
74
As a preliminary exercise to the holding of a postgraduate course in radiation protection, workshops
for post-graduate students from Africa were arranged by the IAEA and held
at the University during the year. Members of the Service, when time permitted, participated actively
in the hosting of the students from the eight African countries, at the Schonland Centre.
Non-ionising Radiation
As in the previous year, a number of enquiries were received from concerned staff members and postgraduate students, of radiation levels around standard microwave ovens and microwave ovens that
were modified for research purposes.
Equipment
As in the past, a number of our staff and students made use of some of the equipment the Service has
at its disposal. The Service has a range of equipment that it makes available to the University
community on a short term loan basis.
Medical School-based Teletherapy Unit
Up until 1995 the Department of Surgery was the most frequent user of this facility. The number of
irradiations undertaken by the Department for 1995 was 584. The figures for the subsequent two
years namely, 1996 and 1997 were 7 and 6 respectively. For the same period ending in December
1998, usage again increased. The figure for the year, was 184. The Central Animal Services, on the
other hand had steadily increased its usage over the same period. Its number of irradiations increased
from 165 in 1995, to 265 in 1996 and 321 in 1997. For 1998 this stabilised to just over the 300 mark
at 309.
The total number of irradiations increased from 333 in 1997 to 628 for the same period last year. The
minor users of the facility in 1998 were the Departments of Medical Biochemistry and the South
African Blood Transfusion Services.
It should again be pointed out that the facility is at least thirty years old. Time and money need
therefore, to be allocated for routine maintenance. The Service shares the concern expressed by the
Central Animal Service and the Department of Surgery regarding the cost of maintaining the facility.
It is clear that an amount has to be set aside for both routine maintenance, and source replacement.
An area often not considered by users of relatively active radioactive sources is question of eventual
disposal of such source.
It should perhaps be stressed that a policy regarding the disposal of large radio-active sources that
have relatively long half-lives and that are no longer needed, needs to be in place to take into account
the non-trivial cost of such eventuality.
Schonland-based Irradiation Facility
The only users of the facility over the past year were researchers from the Schonland Research Centre
and the National Institute of Virology.
75
This under utilisation can be attributed to the activity of the present source which currently less than
one tenth of its original activity.
Acknowledgements
The Service acknowledges with appreciation Prof. R.J. Keddy’s continued involvement and
contribution to the Health Physics Service; both in his capacity as Chairman of the Users’ meeting
and as Honorary Consultant to the Service.
We wish also to record our sincere thanks to the Buying Office and all the departmental radiationsupervisors, for their assistance and contributions. It can be said that their input contributed much to
the smooth running of the Service.
TL Nam
October 1999
76