The T506 Experiment: Electromagnetically-Induced Radiation Damage to Solid-

State Sensors

Test Facilities Users WorkshopSLAC, September 17 2014

Bruce SchummSanta Cruz Institute for Particle Physics

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T-506 Motivation I: The ILC BeamCal

ILC Detector

BeamCal: accepts electrons (positrons) scattered between

5 and 50 MRad

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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…)

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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”) resonancesResonance at 10-20 MeV (~Ecritical)

• PhotoproductionThreshold seems to be about 200 MeV

• Nuclear Compton scatteringThreshold at about 10 MeV; resonance at 340 MeV

These are largely isotropic; must have most of hadronic component develop near sample

2 X0 pre-radiator; introduces a little

divergence in shower

Not shown: 4 X0 and 8 X0 radiators

just before and after sensor

Sensor sample

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Detector Fluence Distribution (per incident e-)

Radius (cm)

Flu

ence

(p

arti

cles

per

cm

2)

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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Dose Rates (Including 1 cm2 Rastering)Mean fluence per

incident e-

Maximum dose rate (10.6 GeV; 10 Hz; 150pC per pulse; end of 2013):

28 Mrad per hour

Confirmed with RADFET to within 10%

Approximate dose rate: 1.7 Mrad per GeV-nA-Hour

LCLS and ESAUse pulsed magnets in the beam switchyard to send beam in ESA.

Mauro Pivi SLAC, ESTB 2011 Workshop, Page 9

ESTB parameters

0.25 nC

Parameters ESA

Energy 15 GeV

Repetition Rate 5 Hz

Charge per pulse 0.35 nC

Energy spread, E/E 0.02%

Bunch length rms 100 m

Emittance rms (xy) (4, 1) 10-6 m-rad

Spot size at waist (x,y < 10 m

Drift Space available for experimental apparatus

60 m

Transverse space available for experimental apparatus

5 x 5 m

3..5-10.5 (for now)

Up to 10 Hz!

≤ 0.15 nC

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T506 Doses for Si Diode Sensors

“P” = p-type “N” = n-type“F” = float zone “C” = Czochralski

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Sensor +FE ASIC

DAQ FPGA with Ethernet

Charge Collection Apparatus at SCIPP

(UCSC Campus)

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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 user

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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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Channel-over-threshold profile

Efficiency vs. threshold

Median Collected Charge

Charge Collection Measurement2.3 MeV e- through sensor into scintillator