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Update from SLAC ESTB T-506 Irradiation Study at ECFA Linear Collider Workshop

This update provides the latest results and findings from the SLAC ESTB T-506 Irradiation Study presented at the ECFA Linear Collider Workshop. Topics covered include irradiation of sensors, extended annealing results, charge collection measurement, and assessment of radiation damage.

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Update from SLAC ESTB T-506 Irradiation Study at ECFA Linear Collider Workshop

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  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 Extended annealing results for GaAs Extended results on 4H-SiC, including annealing and high-bias studies New results on 300 Mrad exposure of n-type float-zone sensor Si dioe power-draw study based on p-type and n-type ~300 Mrad exposures

  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. Recent T506 Exposures 7

  8. 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 8

  9. 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 9

  10. 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 10

  11. Assessing the Radiation Damage 11

  12. Charge Collection Measurement For pad sensors use single-channel readout Daughter-board Low-noise amplifier circuit (~300 electrons) 12

  13. Charge Collection Apparatus • Readout: 300 ns 2.3 MeV e- through sensor into scintillator Sensor + FE ASIC DAQ FPGA with Ethernet 13

  14. 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 14

  15. Results 15

  16. GaAs 21 Mrad Exposure 16

  17. 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 17

  18. GaAs Charge Collection (21 Mrad Exposure) 21 Mrad Exposure Collected Charge (fC) Vbias (V) Charge Collection v. Bias and Annealing Temp 18

  19. GaAs Charge Collection (21 Mrad Exposure)  Try even higher annealing temperatures  Higher exposure in next T506 run 21 Mrad Exposure Vbias = 600 V Slice at VB=600 vs. function annealing temp 19

  20. 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 20

  21. SiC Results Bohumir Zatko, Slovak Institute of Science 4H-SiC crystal geometry Irradiated to 80 Mrad 21

  22. SiC Dark Current Before/After Annealing 80 Mrad Exposure 22

  23. SiC Charge Collection after 80 Mrad @600 V, ~25% charge collection loss (60C annealing) 80 Mrad Exposure 23

  24. Si Diode Results • P-Type Float Zone (PF) to 270 Mrad • N-Type Float Zone (NF) to 300 Mrad 24

  25. PF Charge Collection after 270 Mrad @600 V, ~20% charge collection loss (60C annealing) 25

  26. 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) 26

  27. NF Charge Collection after 300 Mrad After normalizing for sensor area, results are similar to those for the PF sensor. Sensor area = 0.1 cm2 Temperature  -15 C 27

  28. NF Charge Collection after 300 Mrad @600 V, ~55% charge collection loss (32C annealing) 28

  29. Luc d'Hauthuille Bruce Schumm University of California, Santa Cruz Power Draw of the Beam Calorimeter as a function of Temperature & Radiation Dosage

  30. Assumptions Power modeled as a function of radiation and temperature Power drawn scales linearly with radiation dosage Temperature dependent IV data was taken at SCIPP for a Si sensor exposed to 270 MRads of radiation after a 60˚C annealing process, by Cesar Gonzalez & Wyatt Crockett. A 3rd degree polynomial was fit to this I vs. T data, for a Bias Voltage = 600V

  31. Overview • The LCSIM framework was used to compute the energy deposited from 10 simulated background events (bunch crossings at 500 GeV collision energy) • Energy deposited was then extrapolated for 3 years of runtime, and converted to radiation dosage • Temperature was input and combined with radiation dosage to compute the power draw for each mm^2 pixel, at each layer, for 600V bias (charge-collection about 90% after 270 Mrad) • Power draw of these pixels was plotted on a heatmap for a range of temperatures (-7, 0,7, 15 ˚C)

  32. IV Curves at various Temperatures

  33. Polynomial Fit for Temperature Dependent Current (600 V)

  34. Model for Power Draw Using these assumptions, power drawn by a pixel is: P(R,T) = (R/270MRads)*(600V)*I(T) where R is radiation dosage, T is temperature, 600V is the Bias Voltage and I(T) is the current given by the fit.

  35. Layers 2 & 10 of BeamCal at T = 0˚C P_max = 4.59 mW (for a single mm2 pixel)

  36. Power Drawn(Watts) of BeamCal collapsed T = -7 ˚C T = 0 ˚C P_total = 4.467 W P_total = 11.01 W P_max = 1.86 mW P_max = 4.59 mW (for a single pixel) (for a single pixel)

  37. Total Power Draw (3 Years of Running with Si Diode Sensors

  38. Summary • GaAsafter 20 Mrad exposure retains low current. Charge loss severe but recovers with annealing. Need to try higher annealing temp and then larger exposure. • 4H-SiCafter 80 Mradexposure suffers ~25% CC loss; possible annealing gain at higher temperatures. Currents remain low.  Try higher temp and larger exposure also. • PF and NF silicon diodes shows significant CC after 3-year equivalent dose. Significant currents but overall power draw still low. Additional diode sensors (up to ~600 Mrad) await evaluation. • Sapphire sensors now characterized and mounted. Low-noise amplifier being commissioned. 38

  39. BACKUP 39

  40. 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 40

  41. SiC CC Before/After Annealing 80 Mrad Exposure 41

  42. 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 42

  43. Summer 2013: Initial Si Doses “P” = p-type “N” = n-type “F” = float zone “C” = Czochralski 43

  44. 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?

  45. 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

  46. 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 46

  47. 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

  48. Charge Collection Measurement For strip sensors use multichannel readout Median Collected Charge Channel-over-threshold profile Efficiency vs. threshold 48

  49. 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 49

  50. Results: NF Sensor to 90 Mrad, Plus Annealing Study Dose of 90 Mrad Limited beneficial annealing to 90oC (reverse annealing above 100oC?) 50

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