1. BeamCal-Related SiD Work at SCIPP
LCWS 2016
Aiina Center & MALIOS
Morioka, Iwate, Japan
December 5-9, 2016
Bruce Schumm
UC Santa Cruz Institute for Particle Physics 1

2. Main Points and Updates
Radiation damage studies (T506)
Power dissipation simulation
Beam Collision Parameters
Degenerate SUSY

3. Mauro Pivi SLAC, ESTB 2011 Workshop, Page 3
LCLS and ESA
Use pulsed magnets in the beam switchyard to send beam in ESA.
Mauro Pivi SLAC, ESTB 2011 Workshop, Page 3 3

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

5. Both irradiated to 300 Mrad
Summer 2016: LumiCal Sensors and Industrial Sapphire
LumiCal sensor fragment via Sahsa Borisov, Tel Aviv
Industrial sapphire sensor courtesy of Sergej Schuwalow, DESY Zeuthen
Both irradiated to 300 Mrad 5 5

6. Other Recent Exposures and Summary
December 2015, Summer 2016 offered high-rate exposures: 10 24hr days of ~20 Mrad/hr
Sensor Type
Notable Exposures (Mrad)
GaAs
20, 100
SiC 80
Si PF
270, 570
Si NF
300
Si PC
600
Si NC
290
Red indicates results available; others await evaluation
Operated at GeV at close to 1 nA 6 6

7. Si Diode Results P-Type Float Zone (PF) to 270 Mrad
N-Type Float Zone (NF) to 300 Mrad
Just by way of reminder (reported at Santander in June) 7 7

8. PF Charge Collection after 270 Mrad
@600 V, ~20% charge collection loss (60C annealing) 8 8

9. PF I-V after 270 Mrad Exposure (-10 C)
At 600 V, about 80 A (0.05 W) per cm2 (sensor area ~ cm2)
Not much improvement with annealing
270 Mrad Exposure 9 9

10. NF Leakage Current 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 10 10

11. NF Charge Collection after 300 Mrad
@600 V, ~55% charge collection loss (32C annealing) 11 11

12. New Results 12 12

13. LumiCal Sensor (N-Type)
Fragment cleaved from broken sensor provided by Tel Aviv
After treatment (heat, UV light) were able to bias center strip to ~150V
After 300 Mrad irradiation, could bias to > 300 V 13 13

14. N-Type LumiCal Prototype Fragment
Typical (~20 A/cm2) post-irradiation currents
300 Mrad Exposure 14 14

15. N-Type LumiCal Prototype Fragment Sensor via Sasha Borisov, Tel Aviv
Significant charge loss; annealing studies continue
300 Mrad Exposure
Sensor via Sasha Borisov, Tel Aviv 15 15

16. Industrial Sapphire Sensor provided by Sergej Schuwalow
Short collection length for mobile carriers  intrinsically small signals
Current low (< 10 nA) after irradiation 16 16

17. Industrial Sapphire Charge Collection
Low pre-irradiation charge-collection and significant charge loss after irradiation
Sensors via Sergej Schuwalow, DESY Zeuthen
500 m thick Al2O3
300 Mrad Exposure 17 17

18. Industrial Sapphire High-Bias Annealing Trends
Annealing does not seem to significantly restore charge collection
500 m thick Al2O3
300 Mrad Exposure
Sensors via Sergej Schuwalow, DESY Zeuthen 18 18

19. Summary and Outlook
For all tested technologies, so far only p-type Si seems to maintain good charge collection as dose  1 Grad (might have been expected…)
LumiCal sensors might work (charge collection and currents typicalfor n-type), but not optimal
Currents do develop, but preliminary estimates have suggested overall power draw remains quite tolerable; these estimates are being refined (FLUKA simulation)
A number of highly-irradiated Si Diode samples (300, 600 Mrad) await characterization, as does a 100 Mrad GaAs exposure (but poor performance was observed for 20 Mrad for GaAs)

20. Power Draw of the Beam Calorimeter as a function of Temperature & Radiation Dosage
Reminder of studies already presented
Caveat
Discussion of refined studies underway
(Original studies done by Luc D’Hauthille,
UCSC undergraduate)

21. Assumptions
Power modeled as a function of radiation and temperature based on T506 results (see above)
Power drawn scales linearly with radiation dosage
A 3rd degree polynomial was fit to this I vs. T data, for a Bias Voltage = 600V

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

23. P(R,T) = (R/270MRads)*(600V)*I(T)
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.

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

25. Total Power Draw (3 Years of Running with Si Diode Sensors
Operating Temperature (0C)
Total Power Draw (W)
Maximum for 1mm2 Pixel (mW) 15 56 23 7 25 10 11
4.6 -7
4.5
1.9

26. In T506, beam uniformly illuminates a ~1 cm2 area
Caveat
In T506, beam uniformly illuminates a ~1 cm2 area
At ILC, pair background is spread across ~15cm radius BeamCal face
Most neutrons are produced near shower max, but emanate isotropically 26 26

27. Actual irradiation distribution is spread across face of BeamCal (albeit fairly peaked at origin)27 27

28. Away from shower max, direct irradiation may be small, but the peripheral neutron flux must be considered ! 28 28

29. Will assume that damage is entirely due to neutron flux
Refinement
FLUKA-based model of BeamCal under development (Benjamin Smithers, UCSC undergraduate, with help from Anne Schuetz)
Will assume that damage is entirely due to neutron flux
T506 results will provide calibration factor for damage vs. neutron fluence 29 29

30. Using the BeamCal to Obtain Information about Collision Parameters (Earliest results from new MDI initiative) 30 30 30

31. Contributors Goal Luc D’Hauthuille, UCSC Undergraduate (thesis)
Anne Schuetz, DESY Graduate Student
Christopher Milke, UCSC Undergraduate
With input from Glen White, Jan Strube, B.S.
Goal
Idea is to explore the sensitivity of various beamstrahlung observables, as reconstructed in the BeamCal, to variations in IP beam parameters. The sensitivity will be explored with various different BeamCal geometries.

32. Of these, we believe the following can be reconstructed in the BeamCal:
Total energy and its r, 1/r moment
Mean depth of shower
Thrust axis and value Mean x and y positions
Left-right, top-bottom, and diagonal asymmetries

33. IP Parameter Scenarios
Thanks to Anne Schuetz and Glenn White
Relative to nominal:
Increase beam envelop at origin (via -function), for electron and positron beam independently, by 10%, 20%, and 30%
Move waist of electron and positron beam (independently) back by 100m, 200 m, 300 m.
Introduce correlations between X,Z and X,Y and X’,Y
Details at

34. Example: Total Deposited Energy e+ and e- beam envelope scan
Average of 8 Beam Crossings
e+ and e- beam envelope scan

35. Going Forward…
100 beam crossings of statistics available (above plots used only 8)
Need to finish coding observables
Need to simulate the new correlation trajectories from Anne and Glen
And then, the actual point of the study: take
trajectories for which the results are interesting,
and study how the sensitivity depends upon
BeamCal geometry (nature of the cutout)

36. Degenerate SUSY Just an outline – more of our work is focusing here
Complete transition to new framework (almost done)
Need to find a way to reduce two-photon background cross section by 102 before generation (data storage limitations)
Hadronic system event variables, including thrust and perhaps also razor variables
Develop fast MC for BeamCal reconstruction
Develop “prediction algorithm” to reject two-photon events for which neither the electron nor positron strike the BeamCal
Explore interference of Bhabha events with two-photon background rejection
And again, the actual point of the study is to use all this to explore the reach in mass splitting (stau - 10) as a function of BeamCal geometry, presence of anti-DID, and hermeticity…

37. BackUp
BackUp…
Bruce Schumm

38. GaAs
21 Mrad Exposure 38 38

39. 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 39 39

40. GaAs Charge Collection (21 Mrad Exposure)
Collected Charge (fC)
Vbias (V)
Charge Collection v. Bias and Annealing Temp 40 40

41. 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 41 41

42. Compare to Direct Electron Radiation Results (no EM Shower)
A bit better performance than direct result
kGy
Pre-anneal
Post-anneal at room temp
Georgy Shelkov, JINR
1000 kGy = 100 Mrad 42 42

43. SiC Results Bohumir Zatko, Slovak Institute of Science
4H-SiC crystal geometry
Irradiated to 80 Mrad 43 43

44. SiC Dark Current Before/After Annealing
80 Mrad Exposure 44 44

45. SiC Charge Collection after 80 Mrad
@600 V, ~25% charge collection loss (60C annealing)
80 Mrad Exposure 45 45

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

47. 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

48. 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)

49. IV Curves at various Temperatures

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

51. P(R,T) = (R/270MRads)*(600V)*I(T)
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.

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

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

54. Total Power Draw (3 Years of Running with Si Diode Sensors
Operating Temperature (0C)
Total Power Draw (W)
Maximum for 1mm2 Pixel (mW) 15 56 23 7 25 10 11
4.6 -7
4.5
1.9

55. Summary
GaAs after 20 Mrad exposure retains low current. Charge loss severe but recovers with annealing. Need to try higher annealing temp and then larger exposure.
4H-SiC after 80 Mrad exposure 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. 55 55

56. BACKUP 56 56

57. 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 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 57 57

58. SiC CC Before/After Annealing
80 Mrad Exposure 58 58

59. Confirmed with RADFET to within 10%
Dose Rates (Including 1 cm2 Rastering)
Mean fluence (cm-2) per incident e-
Confirmed with RADFET to within 10%
Maximum dose rate (e.g GeV; 10 Hz; 150 pC per pulse):
20 Mrad per hour 59 59

60. Summer 2013: Initial Si Doses
“P” = p-type “N” = n-type
“F” = float zone “C” = Czochralski 60 60

61. 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

62. Charge Collection Measurement
For strip sensors use multichannel readout
Median Collected Charge
Channel-over-threshold profile
Efficiency vs. threshold 62 62

63. GaAs I-V after 21 Mrad Exposure (-10 C)
At 600 V, about 0.7 A ( W) per cm2
GaAs IV
GaAs
Dose of 21 Mrad
Post-anneal
Pre-anneal 63 63

64. Results: NF Sensor to 90 Mrad, Plus Annealing Study
Dose of 90 Mrad
Limited beneficial annealing to 90oC (reverse annealing above 100oC?) 64 64

65. ~15% charge loss at 300 ns shaping
Results: NC sensors
Dose of 220 Mrad
Incidental annealing
~15% charge loss at 300 ns shaping 65 65

66. Results: PF sensors
Doses of 5 and 20 Mrad
No annealing 66 66

67. Results: PC sensors
Dose of 20 Mrad
No annealing 67 67

68. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993)
Departure from NIEL (non-ionizing energy-loss) scaling observed for electron irradiation
NIEL e- Energy
2x MeV
5x MeV
1x MeV
2x 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? 68 68

69. Results: NF sensor for low dose
Doses of 5 and 20 Mrad
No annealing 69 69