Radiation Damage Studies for Solid State Sensors Subject to MRaD Doses [T506 12-2015 Follow-on] Bruce Schumm UC Santa Cruz December 29 2015

The Issue: ILC BeamCal Radiation Exposure Covers between 5 and 40 miliradians Radiation doses up to 100 MRad per year Radiation initiated by electromagnetic particles (most extant studies for hadron –induced) EM particles do little damage; might damage be come from small hadronic component of shower? 2 2

Radiation Damage in Electromagnetic Showers Folk wisdom: Radiation damage proportional to non-ionizing component of energy loss in material (“NIEL” model) BeamCal sensors will be embedded in tungsten radiator Energy loss dominated by electromagnetic component but non-ionizing contribution may be dominated by hadronic processes

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 4 4

Daughter Board Assembly Pitch adapter, bonds Sensor 1 inch 5 5

Actual Setup In ESA Beamline 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

Proposed split radiator configuration 5mm Tungsten “pre” 13mm Tungsten “post” Separated by 1m Fluence (particles per cm2) 1.0 2.0 3.0 7 Radius (cm) 7

Rastering Need uniform illumination over 0.25x0.75 cm region (active area of SCIPP’s charge collection measurement apparatus). Raster in 0.05cm steps over 1x1 cm, assuming fluence profile on prior slide (see next slide for result) Exposure rate: 100 MRad at 0.75 nA and 15 GeV  ~ 6 Hours

Charge Collection Apparatus Sensors DAQ FPGA with Ethernet Sensor + FE ASIC Recently upgraded for multiple samples P-type and N-type sensors Float-zone and Magnetic Czochralski bulk Will maintain 0-5o C during irradiation Continue studies begin in 2013 9 9

Summer 2013: Initial Si Diode Sensor Doses “P” = p-type “N” = n-type “F” = float zone “C” = Czochralski 10 10

Other Notable Exposures GaAs pad sensors via Georgy Shelkov, JINR Dubna Irradiated with 5.7 and 21.0 Mrad doses of electromagnetically-induced showers Also, PF pad sensor irradiated to ~300 MRad 11 11

NC charge collection after 200 Mrad ~15% charge loss at 300 ns shaping Dose of 220 Mrad Incidental annealing ~15% charge loss at 300 ns shaping 12 12

PF Current after 300 Mrad Exposure At 600 V, about 75 A (0.05 W) per cm2 (sensor area ~ 0.025 cm2) 13 13

PF Charge Collection after 300 Mrad At 600 V, about 30% charge collection loss 14 14

GaAs Charge Collection: 5.7 Mrad Exposure 15-20% charge loss at 300 ns shaping Seems to worsen with annealing Sensor detached at 30o annealing step GaAs Dose of 5.7 Mrad 15 15

GaAs Dark Current (-100 C) O(100 nA/cm2) after 6 MRad irradiation Not observed to improve with annealing 16 16

GaAs I-V after 21 Mrad Exposure (-10 C) At 600 V, about 0.7 A (0.0005 W) per cm2 GaAs IV GaAs Dose of 21 Mrad Post-anneal Pre-anneal 17 17

Including 1 HR room-temperature annealing GaAs Charge Collection after 21 Mrad Exposure and Room Temperature Annealing GaAs Dose of 21 Mrad Including 1 HR room-temperature annealing Pre-irradiation Post-irradiation, pre-anneal Post-irradiation, RT anneal 18 18

GOALS FOR THIS RUN Continue exploration of promising Si Diode sensors 300 Mrad exposures for NF, PC, NC type sensors Put PF back in for another 300 Mrad

But: Are electrons the entire picture? G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993) NIEL e- Energy 2x10-2 0.5 MeV 5x10-2 2 MeV 1x10-1 10 MeV 2x10-1 200 MeV Damage coefficients less for p-type for Ee- < ~1GeV (two groups); note critical energy in W is ~10 MeV But: Are electrons the entire picture? 20 20

BACKUP

Incorporate hadronic processes by placing sensor at maximum of tungsten-induced shower Up to 10W beam absorption; operate at about freezing to avoid annealing 22 22

Summer 2015: SiC and Further Si Exposure SiC sensor array provided by Bohumir Zatko, Slovak Institute of Science Irradiated to ~100 Mrad dose Also, PF pad sensor irradiated to ~300 MRad 23 23