Project Title: MRI Consortium: Developments for a Novel Pixel Tracking
Layer for the ATLAS Detector
Annual Project Report for first year.
Date September 2, 2011
We are making excellent progress on the development of the novel pixel
layer. In particular we are ahead of most of our milestones and the detector
layer is planned for installation during the 2013-2014 shutdown of the LHC
accelerator.
Progress reports for each institution follow below, some
highlights are as follows:
The first version of the frontend chip has worked extremely well and we will
be submitting the final chip for fabrication by the middle of September. The
prototype chip has been used in an extensive beam and radiation program to
qualify sensors that have been specially developed for the pixel detector
layer. These sensors are planar n-on-n silicon sensors which are 200
microns thick with slim, 200 micron, edges and 3-D silicon sensors which
are 230 microns thick with 200 micron edges. The frontend chip and 3-D
sensors are new to the field and have the potential for applications in other
experiments. At present both planar and 3-D sensors function well and it is
likely that both will be used in the final device, chosen for use in areas of the
detector where they offer maximum advantage and keep costs low. The
planar are best for tracks close to normal incidence while the 3-D should
allow better performance for inclined tracks because of a more predictable
field distribution within the silicon.
Important work expected during remainder of 2011: tests of the final
frontend chip, and production and tests of prototype staves which combine a
number of bump bonded sensors on a mechanical structure with readout
cables.
University of Iowa
Prototype of the electronic cards in the LVPP4 have been constructed by
The U. of Iowa technicians. The original schematics from Wuppertal were
modified according to the IBL needs, and constructed at the electronic
workshop at Iowa with some help from the engineers. Two opto-isolator
cards, an interboard card and a backpanel card were completed, brought to
CERN and preliminary load tests done. These proved satisfactory. A
complete test with the PVSS requires an independent test stand setup. This is
underway at CERN with Mallik and an Iowa postdoc. A Weiner power
supply and a partially full LVPP4 crate which requires a special transformer,
its associated cable, a strong front panel which supports the stress of the
connected cards and the heavy cable is being assembled. A test with Stave0
is planned for the beginning of October and LVPP4 is expected to
participate in the test.
University of Hawaii
Sherwood Parker has continued his work on novel 3-D pixel sensors. This
has included beam tests and advice on design and processing. This effort
has been very successful with the first demonstration of good production
yield of significant numbers of full size (2cmx2cm) sensors. These have
performed well in the beam test and the present plan is that about 25% of the
IBL detectors will be of this type. They will be arrayed to cover the large
rapidity region where they offer advantages because of the electric field
distribution in the case of highly inclined tracks.
SUNY Stony Brook
Stupak (grad student) implemented the initial geometry layout of IBL in
ATLAS simulation software and later participated in the IBL performance
task force, that showed vast improvement in the physics reach due to the
addition of the IBL to the current ATLAS pixel detector. This work
culminated in Technical Design Report, which was later approved by the
ATLAS collaboration and the LHCC. DeWilde (grad student) and
Tsybychev are co-authors of three NIM papers resulting from the 3D pixel
sensor test beam work that included measurements of charge collection,
tracking efficiency and charge sharing between pixel cells, as a function of
track incident angle, and were performed with and without a 1.6 T magnetic
field oriented as the ATLAS inner detector solenoid field. Those studies
have culminated in the recent ATLAS sensor technology review committee
recommendation to populate 25% of the modules with 3-D pixel sensors,
covering the forward region of the detector, where they expect to perform
better than planar sensors after irradiation.
Oklahoma State and University of Oklahoma
Oklahoma State and the University of Oklahoma work together on the Optobox part of the IBL. This includes three flavors of optobox. The lead for
Oklahoma is engineer Rusty Boyd. Oklahoma State has employed EE
student Steven Welch. A list of the major components of an optobox and the
current status of the components is as follows:
Major Components of an Optobox
 Optobox connector boards for B,D boards
 Optobox assembly
 Optoboards
 Optobox Motherboard
 Optobox Connector board assembly
Component Status
 B Optoboard – Prototype in Assembly
 D Optoboard – Design Phase
 B Connector Board – Prototype in Assembly
 D Connector Board – Prototype in Assembly
 Prototype Motherboard – Design Phase
 B Optobox Prototype – In Manufacturing
UC Santa Cruz
In this first year of the IBL MRI grant, we have continued our evaluation of
silicon sensors with regard to radiation hardness and charge collection
efficiency. The IBL collaboration has decided to proceed with planar n-on-n
sensors for the IBL staves but to continue fabrication of sufficient 3-D
sensors to possibly populate the outer 25% at the ends of each stave along
the beam direction. This latter option is due to the improved performance of
3-D sensors for steeply inclined tracks. The final decision on which
technology to use for the outer 25% will be made after modules are built but
before stave integration begins.
As a result of our R&D work on “slim-edge” technology and our initial tests
of its application to n-on-n devices, lead by Vitaliy Fadeyev, some of the non-n planar sensors will be fabricated on wafers with lattice structure 100
instead of the normal 111. This is to facilitate tests of the UCSC “slimedge” technology on these wafers. Further tests of these wafers are
continuing.
The electrical services are still in the design and early prototyping phase.
Our engineer Ned Spencer was asked to direct the grounding and shielding
aspects of the design given the success of his work on the now operating
ATLAS SCT detector. He has been working closely with our collaborators
at SLAC and CERN to assure effective shielding of the entire IBL structure
as well as proper routing of power, signal and ground connections. There
are still design issues with regard to how the services will fit in the available
space and how the integration of those services can be performed within the
space constraints. Another of our technical personnel, Sergei Kachiguine,
was enlisted to design a small interconnect printed circuit board to facilitate
these connections during integration. Sufficient quantities of material have
been purchased for prototype assemblies and that fabrication is proceeding.
As yet, no undergraduate students have contributed to testing but we expect
that to start once prototype assemblies are ready.
Ohio State University
The Ohio State group has fabricated the first prototype optical modules for
the IBL project. This prototype module is designed to communicate with
seven pixel modules instead of eight due to a historical reason. There are
multiple design improvements over the modules built for the current pixel
detector. Consequently the fabrication was considerably simpler and six
modules were successfully fabricated. Four modules were irradiated in
August with 24 GeV/c proton and the degradation in the optical power is
quite modest. The Ohio State group will design and fabricate the next
prototype which will communicate with eight pixel modules as in the final
IBL system. Two undergraduates are involved in the project. They both
participate in the building of the test circuit boards and data acquisition and
analysis of measurements.
Brandeis
During the last year we have established the basic design for the Long Guide
Tube. We have built a prototype that includes the tension rod, internal
RASNIKs (four overlapping 3-point straight line sensors) to monitor the
shape of the tube. We have also built the control system for operating the
LGT. We established the basic operating mode in which feedback from the
internal monitors translates into tube shape parameters and tension
adjustments. This prototype was built at Brandeis then disassembled,
shipped to CERN, and reassembled in building 180 to be used with the Inner
Detector mock-up being built there. Figure 1 is a picture of the LGT, with
control system, installed in a mock-up of the new beam pipe.
The next steps at CERN will be to exercise this prototype in the ID mock-up
and compare the performance to design calculations and further develop the
control program. At Brandeis we will build a beam pipe mock-up with the
same mechanical compliance loading as the actual beam pipe. In addition,
we will work with extruders to develop a pre-stressed aluminum guide tube
to reduce the dependence of the operation on the tension rods.
University of New Mexico
UNM led irradiations of the FE-I4 frontend chip and several candidate
sensor technologies in the LANSCE 800 MeV proton beam. The UNM
contribution included development, submission, and defense of the proposal
for beam time, preparation of the samples, electrical characterization of
some of the devices before and after the run, staffing of shifts and operations
at the beam, real-time monitoring, dosimetry, and facilitation of
communications and transport of devices between LANSCE and ATLAS
collaborators.
During this year we also assessed operation of the HVPP4 Current Monitor
system in the baseline pixel detector to understand design modifications
required for current monitoring in the IBL. At this time it appears that the
primary modification will be to the interrogation of the ELMB status.
Current Monitor work is ongoing.
UC Berkeley
During the first year of the MRI UC Berkeley carried out testing and
characterization of the FE-I4A integrated circuit. First wafers were received
in October 2010. In parallel, one wafer was diced to load single chip test
boards and another 2 wafers were tested on a probe station. Frank Jensen
obtained his UCB undergraduate degree and then worked full time on both
of these activities until April 2011. He is now starting graduate school at the
University of Colorado. The testing included irradiation at the Los Alamos
LANSCE facility in Dec. 2010. Two current USB undergraduate students,
Devlin Mallory and Ming-Yu Hu joined the testing effort part time in early
2011. Based partly on these test results, a design update of the FE-I4 chip
began in February 2011, with a planned submission date of early September
2011. This submission is expected to lead to the production chip for the IBL,
called FE-I4B.
University of Washington
Prototypes of the support tube have been fabricated and are being tested. A
mockup of the detector package has been made allowing tests of the
mechanical items as a unit. The removal of the beam pipe and then insertion
of the IBL is a very delicate process since the space available is extremely
tight. Both Lubatti and two engineers have been at CERN for extended
periods of time in order to have available a first prototype in August, which
is fabricated in 5 sections and assembled and bonded at CERN. In addition,
Washington has been been asked to co-bond a conducting skin to the outer
surface to provide an EM shield. This adds several layers of complications
because it will require a kapton with cooper mesh design that can be cobonded on each piece of the IST and then develop a way of making contacts
from one section to the other after the IST is assembled. This will require
some R&D which involves making short sections of the male-female ends
with some thin conducting sheets to test our procedures and develop a
scheme for electrically connecting from one section to the other.