Results & Updates from SLAC ESTB T-506 Irradiation Study: ECFA Linear Collider Workshop

1. Update from the SLAC ESTB T-506 Irradiation Study ECFA Linear Collider Workshop Palacio de la Magdalena Santander, Cantabria, Spain May 30 – June 5, 2016 Bruce Schumm UC Santa Cruz Institute for Particle Physics

2. Main Points and Updates Reprise: Results from 270 Mrad exposure of p-type float-zone sensor, GaAs Extended results on 4H-SiC, including annealing and high-bias studies New results on 300 Mrad exposure of n-type float-zone sensor

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. Recent T506 Exposures 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. December 2015 Exposure and Summary December 2015: Long, high-rate exposures of all four Si diode types (5 24hr days of ~20 Mrad/hr) Red indicates results available; others await evaluation Operated at 12-15 GeV at close to 1 nA 13

14. Charge Collection Measurement For pad sensors use single-channel readout Daughter-board Low-noise amplifier circuit (~300 electrons) 14

15. Charge Collection Apparatus • Readout: 300 ns 2.3 MeV e- through sensor into scintillator Sensor + FE ASIC DAQ FPGA with Ethernet 15

16. 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 16

17. Results 17

18. GaAs • 5.7 Mrad results • 21 Mrad results have been updated with further annealing studies 18

19. GaAs Dark Current (-100 C) 5.7 Mrad Exposure • O(100 nA/cm2) after 6 MRad irradiation • Not observed to improve with annealing 19

20. 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 20

21. 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 21

22. GaAs Charge Collection (21 Mrad Exposure) 21 Mrad Exposure Collected Charge (fC) Vbias (V) Charge Collection v. Bias and Annealing Temp 22

23. GaAs Charge Collection (21 Mrad Exposure) 21 Mrad Exposure Vbias = 600 V Slice at VB=600 vs. function annealing temp 23

24. 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 24

25. SiC Results Bohumir Zatko, Slovak Institute of Science 4H-SiC crystal geometry Irradiated to 80 Mrad 25

26. SiC Dark Current Before/After Annealing 80 Mrad Exposure 26

27. SiC CC Before/After Annealing 80 Mrad Exposure 27

28. P-Type Float-Zone Sensor • Reminder of results for 270 Mrad irradiation (about 3 years exposure) 28

29. PF Charge Collection after 270 Mrad @600 V, ~20% charge collection loss (60C annealing) 29

30. PF I-V after 270 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) 30

31. NF Charge Collection after 300 Mrad @600 V, ~55% charge collection loss (32C annealing) 31

32. Sensor area = 0.1 cm2 Temperature  -15 C 32

33. 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 33

34. 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 34

35. BACKUP 35

36. 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?

37. 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

38. 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 38

39. 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

40. Charge Collection Measurement For strip sensors use multichannel readout Median Collected Charge Channel-over-threshold profile Efficiency vs. threshold 40

41. 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 41

42. Results: NF Sensor to 90 Mrad, Plus Annealing Study Dose of 90 Mrad Limited beneficial annealing to 90oC (reverse annealing above 100oC?) 42

43. Results: NC sensors Dose of 220 Mrad Incidental annealing ~15% charge loss at 300 ns shaping 43

44. Results: PF sensors Doses of 5 and 20 Mrad No annealing 44

45. Results: PC sensors Dose of 20 Mrad No annealing 45

46. 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? 46

47. Results: NF sensor for low dose Doses of 5 and 20 Mrad No annealing 47