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Update from the SLAC ESTB T-506 Irradiation Study 28 th FCAL Collaboration Meeting

Update from the SLAC ESTB T-506 Irradiation Study 28 th FCAL Collaboration Meeting JINR, Dubna, Russia 21-22 March 2016 Bruce Schumm UCSC/SCIPP. Main Points and Updates. Reprise: Results from 270 Mrad exposure of p-type float-zone sensor New results on GaAs annealing (21 Mrad exposure)

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Update from the SLAC ESTB T-506 Irradiation Study 28 th FCAL Collaboration Meeting

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  1. Update from the SLAC ESTB T-506 Irradiation Study 28th FCAL Collaboration Meeting JINR, Dubna, Russia 21-22 March 2016 Bruce Schumm UCSC/SCIPP

  2. Main Points and Updates Reprise: Results from 270 Mrad exposure of p-type float-zone sensor New results on GaAs annealing (21 Mrad exposure) First results on 4H-SiC Outlook and plans (discussion…)

  3. Irradiating the Sensors 3

  4. LCLS and ESA Use pulsed magnets in the beam switchyard to send beam in ESA. Mauro Pivi SLAC, ESTB 2011 Workshop, Page 4

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

  6. 2 X0 pre-radiator; introduces a little divergence in shower Sensor sample Not shown: 4 X0 “post radiator” and 8 X0 “backstop”

  7. Dose Rates (Including 1 cm2 Rastering) Mean fluence (cm-2) per incident e- Confirmed with RADFET to within 10% Maximum dose rate (e.g. 10.6 GeV; 10 Hz; 150 pC per pulse): 20 Mrad per hour 7

  8. T506 Exposure History 8

  9. Summer 2013: Initial Si Doses “P” = p-type “N” = n-type “F” = float zone “C” = Czochralski 9

  10. Summer 2014: GaAs Doses GaAs pad sensors via Georgy Shelkov, JINR Dubna Irradiated with 5.7 and 21.0 Mrad doses of electromagnetically-induced showers Irradiation temperature 3oC; samples held and measured at -15oC 10

  11. 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 270 MRad 11

  12. Assessing the Radiation Damage 12

  13. Charge Collection Measurement For pad sensors use single-channel readout Daughter-board Low-noise amplifier circuit (~300 electrons) 13

  14. Charge Collection Apparatus • Readout: 300 ns 2.3 MeV e- through sensor into scintillator Sensor + FE ASIC DAQ FPGA with Ethernet 14

  15. Measurement time Pulse-height distribution for 150V bias Mean Pulse Shape Single-channel readout example for, e.g., N-type float-zone sensor Readout noise: ~300 electrons (plus system noise we are still addressing) Median pulse height vs. bias 15

  16. Results 16

  17. GaAs • 5.7 Mrad results • 21 Mrad results have been updated with further annealing studies 17

  18. GaAs Dark Current (-100 C) 5.7 Mrad Exposure • O(100 nA/cm2) after 6 MRad irradiation • Not observed to improve with annealing 18

  19. GaAs Charge Collection: 5.7 Mrad Exposure • 15-20% charge loss at 300 ns shaping • Seems to worsen with annealing • What about higher exposure? 5.7 Mrad Exposure GaAs Dose of 5.7 Mrad 19

  20. GaAs Dark Current (-100 C) for 21 Mrad 45C anneal Room temp anneal 21 Mrad Exposure Before annealing Dark current as a function of annealing temp 20

  21. GaAs Charge Collection (21 Mrad Exposure) 21 Mrad Exposure Collected Charge (fC) Vbias (V) Charge Collection v. Bias and Annealing Temp 21

  22. GaAs Charge Collection (21 Mrad Exposure) 21 Mrad Exposure Vbias = 600 V Slice at VB=600 vs. function annealing temp 22

  23. kGy Compare to Direct Electron Radiation Results (no EM Shower) A bit better performance than direct result Pre-anneal Post-anneal at room temp Georgy Shelkov, JINR 1000 kGy = 100 Mrad 23

  24. SiC Results Bohumir Zatko, Slovak Institute of Science 4H-SiC crystal geometry Irradiated to ~100 Mrad New results! 24

  25. SiC Dark Current Before/After Annealing 100 Mrad Exposure 25

  26. SiC CC Before/After Annealing 100 Mrad Exposure 26

  27. P-Type Float-Zone Sensor • Reminder of results for 270 Mrad irradiation (about 3 years exposure) 27

  28. NF Charge Collection after 300 Mrad @600 V, ~20% charge collection loss (60C annealing) 28

  29. NF I-V after 300 Mrad Exposure (-10 C) • At 600 V, about 80 A (0.05 W) per cm2 (sensor area ~ 0.025 cm2) • Input to example Si Diode power budget study (see next talk, Luc D’Hauthuille) 29

  30. Summary • GaAs charge collection (CC) suffers significant loss at 20 Mrad exposure. Currents low however. • Room-temp annealing worsens CC, but higher temperature yield some recovery • 4H-SiC explored for the first time. • At 100 Mrad, see ~50% CC loss; low currents • Room temperature annealing shows no significant recovery • “PF” silicon diode shows significant CC after 3-year equivalent dose • Annealing to 60C shows some improvement • Moderate (<100 A/cm2) current draw 30

  31. Looking Forward • Cointue GaAs, SiC annealing studies • 300 Mrad exposures of PC, NC, NF silicon diode sensors awaiting evaluation • PF sensor exposed to another 300 Mrad (total 550-600 Mrad); awaiting study • Low-noise amlipfier (<300 electrons) under development for exporation of Sapphire sensors; initial probe evaluation underway. • Ongoing offer for more beam time at SLAC, but large backlog of sensors to study at SCIPP 31

  32. BACKUP 32

  33. T-506 Motivation BeamCal maximum dose ~100 MRad/yr BeamCal is sizable: ~2 m2 of sensors. A number of ongoing studies with novel sensers: GaAs, Sapphire, SiC  Are these radiation tolerant?  Might mainstream Si sensors in fact be adequate?

  34. 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

  35. 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 35

  36. T-506 Idea Embed sample sensors in tungsten: “Pre-radiator” (followed by ~50 cm air gap) spreads shower a bit before photonic component is generated “Post-radiator” brings shower to maximum just before sensor “Backstop” absorbs remaining power immediately downstream of sensor • Realistic EM and hadronic doses in sensor, calibrated to EM dose

  37. Charge Collection Measurement For strip sensors use multichannel readout Median Collected Charge Channel-over-threshold profile Efficiency vs. threshold 37

  38. 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 38

  39. Results: NF Sensor to 90 Mrad, Plus Annealing Study Dose of 90 Mrad Limited beneficial annealing to 90oC (reverse annealing above 100oC?) 39

  40. Results: NC sensors Dose of 220 Mrad Incidental annealing ~15% charge loss at 300 ns shaping 40

  41. Results: PF sensors Doses of 5 and 20 Mrad No annealing 41

  42. Results: PC sensors Dose of 20 Mrad No annealing 42

  43. Departure from NIEL (non-ionizing energy-loss) scaling observed for electron irradiation NIELe- 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? 43

  44. Results: NF sensor for low dose Doses of 5 and 20 Mrad No annealing 44

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