ESTB TEST BEAM PROPOSAL
Submit proposal (2-5 pages) to: Carsten Hast hast@slac.stanford.edu
Date: September 20 2012
Title: Electromagnetic Shower Damage to Silicon Diode Sensors
Principal Investigator: Bruce A. Schumm
Institution:
UC Santa Cruz
Email: baschumm@ucsc.edu
Telephone: 831-459-3034
Members: Vitaliy Fadeyev, Tae Sung Kim, Tom Markiewicz, Forest MartinezMcKinney, Takashi Maruyama, Khilesh Mistry, Bruce Schumm
Description of Physics Goals:
In the current conception of the ILC detector concepts, the Beamline Calorimeter (BeamCal) is
to be the lowest-angle component of instrumentation that intercepts scattered beam particles.
Reaching angles as small as 5 mrad from the ILC beamline, the BeamCal is expected to absorb
large doses of EM radiation – radiation induced by the showers of photons and electrons arising
from the interactions between the intense fields of the colliding beams, and their subsequent
scatters. Doses are expected to reach ~100 MRad per year at shower max in the BeamCal.
Radiation tolerance of silicon sensors to large doses of irradiation has been well studied for the
case of incident hadrons [1]. Collected charge remains at a quite adequate level of 16,000 e- even
after a 50 MRad exposure. P-type bulk silicon was found to be more radiation-tolerant than ntype bulk silicon, due to the absence of type inversion and the collection of an electron-based
signal [2, 3]. There were also early indications of p-type preference from the work done with
electron damage to solar cells [4-6].
To date, studies conducted to assess radiation damage inflicted by incident electromagnetic
particles have been performed with intense beams or sources of pure electromagnetic radiation.
On the other hand it is possible that radiation damage in the core of electromagnetic showers
may be predominantly due to the hadronic component of the shower, which arises from
photoproduction and spallation effects due to excitation of nuclear resonances.
The goal of this study, then, is to explore the tolerance to electromagnetically-induced radiation
of various sensor types (n-type vs. p-type bulk, standard float-zone vs. Czochralski process),
both with and without the inclusion of the hadronic component of electromagnetic showers. We
propose to explore the radiation tolerance of mainstream silicon sensor technologies in realistic
shower spectra and composition. We propose to do this for four different sensor technologies:
both n- and p-type float zone and magnetic Czochralski bulk sensors.
We expect the study to consume approximately 100 hours of dedicated beam time, assuming 1
nA of beam at an average energy of 10 GeV.
Detailed Description of Experimental Apparatus:
15mm
Sample
6mm
W
~1m
W
W
Dry N2
Peltier
Rastoring
Stage
Control
hardware
Fig 2: Rough layout of the target. No fast data-acquisition is required. If needed, the stage holding the
target will be rastered in 0.5 mm steps. The containments will maintain a slow flow of dry nitrogen at a
slight overpressure. A chiller with a capacity of 500W at 0o C will be required to cool the sample and
target. The temperature of the sample will be monitored and relayed to the control room.
We will assess radiation damage by measuring the charge-collection efficiency with an
apparatus on the UCSC campus that we are currently upgrading to run with many
separate samples. To achieve a uniform exposure over the region of illumination of this
apparatus, we will need to raster the beam in 1mm steps over a range of approximately
10x15 mm.
DAQ: There is no need to accumulate data during irradiation. We will monitor several
thermocouples via a USB connection to a PC that will be located by the apparatus and
accessed by remote logon.
Sample Cooling and Nitrogen Environment: To avoid annealing, which modifies the
effects of radiation damage, we will want to run the samples at approximately -10o C. We
intend to do this with Peltier cooling devices in thermal contact with the samples. To
avoid condensation on the samples, we will need to enclose them in a dry nitrogen
environment. The Peltier coolers, and most of the beam, will sink their heat into the
target, which will be liquid-cooled to approximately between 0 and 10 degrees C. We
will require a chiller capable of cooling ~500W at 0 degrees C.
Dosimetry and Dose Reporting: We will need to know the (current)x(energy) product
of the beam to with 5-10%. We will need to have an ongoing report of this integrated
over time. Our exposure durations will be expressed in terms of an amount of chance in
this integral. For example, for the standard split-radiator configuration, 100 MRad
corresponds to 2.3 x 105 nA-Gev-seconds.
Dumping the Beam: Since we propose to place our sensor at shower max, and follow it
with a “backstop” absorber, we are effectively creating a beam dump that surrounds the
sample. We will request that the delivered beam power be restricted to a maximum of
100 W.
Sample Cooling and Nitrogen Environment: To avoid annealing, which modifies the
effects of radiation damage, we will want to run the samples at approximately -10o C. We
intend to do this with Peltier cooling devices in thermal contact with the samples. To
avoid condensation on the samples, we will need to enclose them in a dry nitrogen
environment. The Peltier coolers, and most of the beam, will sink their heat into the
target, which will be liquid-cooled to approximately between 0 and 10 degrees C. We
will require a chiller capable of cooling ~500W at 0 degrees C.
Rastering: We will need to move the beam around the samples in ½-mm steps over a
range of approximately 10x15 mm. We can do this either by moving the beam across the
sample (preferred) or moving the sample about via actuators.
Alignment: In order to ensure that we are measuring the irradiated portion of the sensor
when we assess the charge collection efficiency at SCIPP, we will need to know the
position of the centroid of the End Station A beam to within 1 mm.
Activation: We will need to know if activation of the samples during the run will place
constraints on our moving them around SLAC and taking them off site for measurement.
Summary of Requests for Support
Following is a summary of requests for infrastructure support from the lab. It would be
good to know which of these are easily met.
 Platform (table) with 1 m^2 surface or greater; adjustable height to allow crude
position of the apparatus (e.g. shims under the legs)








Beam rastering over a region of roughly 2cm x 1cm, in 0.5mm steps
A readout of the accumulating value of (beam energy)*(beam current)*(time)
A chiller capable of providing ~500W of cooling at a coolant temperature of 0 C
Dry nitrogen and fittings to run the gas into our environmental box; minimal flow
rate (or perhaps just small overpressue)
One HV line (both polarities) to bias the sample
½ shift of technician to help us set this all up when the time comes.
Total set-up time should be 1 shift.
We would like the maximum beam available, up to 100W total beam power.
Preferred Beam Parameters:
Beam Parameters
Value
Particle Type
Electrons or positrons
Energy (2-13 GeV)
Highest available
Rep Rate (1-5 Hz nominal, bursts up to 120
Hz)
As much as possible
Charge per pulse or number of electrons/pulse
As much as possible
Energy Spread
NA
Bunch Length r.m.s.
NA
Beam Spot size, x-y, emittance
Few mm max
Comments
100 W Maximum
Let us know if
greater than 1mm
Logistics
Space Requirements (include sketch):
We require a platform of roughly 1 m2 (see sketch above). About ½ meter upstream of
this we will need to place a small pre-radiator several inches in radius and about 6mm
thick.
Special Requirements (cooling water, gasses, electricity, magnets, detectors, etc):
As mentioned above, we will need in addition




Beam rastering over a region of roughly 2cm x 1cm, in 0.5mm steps
A readout of the accumulating value of (beam energy)*(beam current)*(time)
A chiller capable of providing ~500W of cooling at a coolant temperature of 0 C
Dry nitrogen and fittings to run the gas into our environmental box; minimal flow
rate (or perhaps just small overpressue)




One HV line (both polarities) to bias the sample
½ shift of technician to help us set this all up when the time comes.
Total set-up time should be 1 shift.
We would like the maximum beam available, up to 100W total beam power.
Estimated installation time:
We believe we will require
 ½ shift of technician to help us set this all up when the time comes.
 Total set-up time should be 1 shift.
Duration of Test and Shift Utilization:
Run
Samples
Exposure
(GRAD)
Exposure Time
per Sample
Total Shifts of
Exposure
Radiator
Placement
1
A,B,C,D
0.003
12 min
¼ shift
F,N
2
A,B,C,D
0.01
40 min
¾ shift
F,N
3
A,B,C,D
0.03
2 hr
1 shift
F.N
4
A,B,C,D
0.10
6.5 hr
3 shifts
F,N
5
TBD
0.10
35 hr
4-5 shifts
F,F
6
TBD
0.10
35 hr
4-5shifts
F,F
Table 1: Proposed run plan, assuming an average delivery of 1 nA at 10 GeV. Samples A and B are the nand p-bulk float zone sensors; samples C and D are the n- and p-bulk Czochralski sensors. Radiator
placements are either “far” (F) or “near” (N) to the sample, and refer to the position of the pre- and postradiator, respectively. The samples to be run in the F,F configuration will explore radiation damage
without the hadronic component, and will be chosen based on the results of the F,N studies. The total
proposed running time is approximately 100 hours.
Desired Calendar dates:
One week to 10 days anytime in February 2012.
Any other aspect of Importance:
See above for specific requirements and requests.
References
[1] G. Kramberger et al., “Comparison of pad detectors produced on different
silicon materials after irradiation with neutrons, protons and pions”, NIM A
612, p. 288 (2010).
[2] G. Casse et al., “First results on charge collection efficiency of
heavily irradiated microstrip sensors fabricated on oxygenated p-type
silicon”, NIM A 518, p.340 (2004).
[3] G. Casse, “Radiation hardness of p-type silicon detectors”, NIM A 612, p.
464 (2010).
[4] J.R. Carter and R.G. Downing, “Charged Particle Radiation Damage in
Semiconductors: Effect of Low Energy Protons and High Energy Electrons on
Silicon”, Interim Technical Final Report, TRW Apce Technology Laboratories,
May 1965.
[5] T. Noguchi and M. Uesugi, “Electron Energy Dependence of Relative Damage
Coefficients of Silicon Solar Cells for Space Use”, Technical Design of the
International PVSEC-5, Kyoto, Japan (1990).
[6] Geoffrey P. Summers et al., “Damage Correlations in Semiconductors
Exposed to Gamma, Electron, and Proton Radiations”, IEEE Transactions on
Nuclear Science 40, p1372 (1993).