The T506 Experiment:
Electromagnetically-Induced
Radiation Damage to Solid-State
Sensors
Test Facilities Users Workshop
SLAC, September 17 2014
Bruce Schumm
Santa Cruz Institute for Particle Physics
T-506 Motivation I: The ILC BeamCal
ILC Detector
BeamCal: accepts electrons
(positrons) scattered
between 5 and 50 MRad
2
T-506 Motivation II
BeamCal maximum dose ~100 MRad/yr
Beam Calorimeter is a sizable: ~2 m2 of sensors.
A number of ongoing studies with novel sensoers:
GaAs, CVD diamond
Are these sensors radiation-hard?
Might mainstream Si sensors be of use? (some
reasons for optimism…)
3
Departure from NIEL (non-ionizing energy-loss) scaling
observed for electron irradiation
NIEL
e- Energy
2x10-2 0.5 MeV
5x10-2 2 MeV
1x10-1 10 MeV
2x10-1 200 MeV
G.P. Summers et al., IEEE Trans
Nucl Sci 40, 1372 (1993)
Also: for ~50 MRad illumination of 900 MeV electrons, little
loss of charge collection seen for wide variety of sensors
(S. Dittongo et al., NIM A 530, 110 (2004)
But what about the hadronic component of EM shower?
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Hadronic Processes in EM Showers
There seem to be three main processes for generating
hadrons in EM showers (all induced by photons):
• Nuclear (“giant dipole”) resonances
Resonance at 10-20 MeV (~Ecritical)
• Photoproduction
Threshold seems to be about 200 MeV
• Nuclear Compton scattering
Threshold at about 10 MeV;  resonance at 340
MeV
 These are largely isotropic; must have most of
hadronic component develop near sample
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2 X0 pre-radiator;
introduces a little
divergence in
shower
Sensor sample
Not shown: 4 X0
and 8 X0 radiators
just before and after
sensor
Fluence (particles per cm2)
Detector Fluence Distribution (per incident e-)
For later charge
collection
measurement, must
have ~1cm2 uniformly
illuminated area
Raster sensor
across beam
1.0
2.0
3.0
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Radius (cm)
Dose Rates (Including 1 cm2 Rastering)
Mean fluence per
incident e-
Confirmed
with RADFET
to within 10%
Approximate dose rate: 1.7 Mrad per GeV-nA-Hour
Maximum dose rate (10.6 GeV; 10 Hz; 150
pC per pulse; end of 2013):
28 Mrad per hour
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LCLS and ESA
Use pulsed magnets in the beam switchyard to send
beam in ESA.
Mauro Pivi SLAC, ESTB 2011 Workshop, Page 9
ESTB parameters
Parameters
ESA
Energy
3..5-10.5 (for now)
Repetition Rate
Up to 10 Hz!
Charge per pulse
≤ 0.15 nC
0.25 nC
15 GeV
5 Hz
0.35 nC
Energy spread, sE /E
0.02%
Bunch length rms
100 mm
Emittance rms (gex,gey)
(4, 1) 10-6 m-rad
Spot size at waist (sx,y)
< 10 mm
Drift Space available for experimental
apparatus
Transverse space available for experimental
apparatus
60 m
5x5m
T506 Doses for Si Diode Sensors
“P” = p-type
“F” = float zone
“N” = n-type
“C” = Czochralski
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Charge Collection
Apparatus at SCIPP
(UCSC Campus)
Sensor +
FE ASIC
DAQ FPGA
with Ethernet
12
Results: NC sensors
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Results: NF sensors high dose
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Other T506 Exposures
• Two bulk GaAs sensors
–
–
–
5 Mrad
20 Mrad
Charge-collection evaluation underway
• LCLS Upgrade attachment samples
• T506 apparatus/infrastructure can be
made available upon request
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T506 Plans for 2015
• Exposures must be at least 100
Mrad to be of use
• Low-energy/low-current running
probably not of use
• Second kicker-magnet probably solves
everything (T506 could make use of
frequent high-energy running which is
best for it anyway!)
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T506 Wish List for 2015
•
“NC” sensor to 500 Mrad
•
“NF” sensor to 250+ Mrad
•
“PF”, “PC” sensors to 100 Mrad
•
GaAs sensor to 100 Mrad
5 GeV, 0.75 nA  ~200 Hrs (20-25 shifts)
13 GeV, 1 nA  ~50 Hrs (5-7 shifts)
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Summary and Conclusions
• The 2014 re-configuration of the T506 target
has made it trustworthy and easy to use
• Running to date has shown promise for
performance of “everyday” Si Diode sensors at
ILC BeamCal dose rates
• With second kicker magnet, ESTB is up to the
task of exploring full BeamCal dose rates
• T506 target also used for other exposures,
including GaAs and LCLS upgrade samples
• T506 apparatus can be made available for
controlled irradiation studies for any interested
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user
BACKUP
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Results: NF sensors low dose
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Results: PC sensors
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Results: PF sensors
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Charge Collection Measurement
2.3 MeV e- through sensor into scintillator
Median
Collected
Charge
Channel-overthreshold profile
Efficiency vs.
threshold
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