1. Progress on ILC Forward Calorimetry by the FCAL Collaboration
AWLC17, SLAC
June 26-30, 2017
Bruce Schumm
UC Santa Cruz Institute
for Particle Physics
Representing the FCAL Collaboration 1

2. FCAL detector purposes in future e+e- linear accelerators
Yan Benhammou
FCAL detector purposes in future e+e- linear accelerators
LumiCal :
Precise integrated luminosity measurements (Bhabha events)
Extend calorimetric coverage to small polar angles. Important for physics analysis
LHCal :
Extend the hadronic calorimeter coverage
BeamCal :
Measure instant luminosity
tagging of high energy electrons to suppress backgrounds to potential BSM process
shielding of the accelerator components from the beam-induced background
providing supplementary beam diagnostics information extracted from the pattern of incoherent-pair energy depositions

3. ILC Layout
BeamCal +Z
LHCal
LumiCal
CLIC Layout

4. FCAL detector designs in future e+e- linear accelerators
Yan Benhammou
FCAL detector designs in future e+e- linear accelerators
LumiCal :
Electromagnetic sampling calorimeter
layers of 3.5 mm thick tungsten plates with 1 mm gap for silicon sensors (30 for ILC, 40 for CLIC)
LHCal :
Sampling Calorimeter
29 layers of 16mm thickness. Absorber : tungsten or iron
BeamCal:
Sampling calorimeter based on tungsten plates (30layers for ILC, 40 layers for CLIC)
Due to large dose (100 Mrad/yr of EM particles), rad hard sensors sought

5. LumiCal sensor Yan Benhammou channels: 1 - 64
4 sectors: L2 L1 R1 R2
channels:
Outer active radius R = mm
3 x 100 μm guard rings
Silicon senor, 320 mm thickness
DC coupled with read-out electronics
p+ implants in n-type bulk
64 radial pads, pitch 1.8 mm
4 azimuthal sectors in one tile, each 7.5 degrees
12 tiles makes full azimuthal coverage
40 modules were produced by Hamamatsu
Inner active radius R = 80.0 mm

6. LumiCal test at CERN in 2014 Yan Benhammou Energy fraction
4 LumiCal modules equipped with dedicated electronics (32 channels) glued on a 2.5 mm PCB
3.5 mm between tungsten plates (fill-factor of ½)
Tested in test beam at PS with 5 GeV e-/m
Energy fraction
Extracted Moliere radius :
24.0 ± 0.6 (stat.) ± 1.5 (syst.) mm

7. Sasha Borysov 7 7

8. Sasha Borysov 8 8

9. Sasha Borysov 9 9

10. 10
Sasha Borysov 10

11. Sasha Borysov 11 11

12. Sasha Borysov 12 12

13. Alternative BeamCal Designs
Makes use of industrial Sapphire?
Inexpensive
Radiation tolerant (?)
But small signal (short mean free path)
Baseline Design
Standard sampling configuration
GaAs sensor planes
2013 DESY Beam Test (beam parallel to sensors)
Goal is to construct and test prototype in 2018 13
Sergej Schuwalow 13

14. Electronics 14 14

15. LumiCal readout in 2014 Yan Benhammou Signal to noise ratio ~19
Development of an ASIC for the 2014 test beam
Charge amplifier shaper with different gain (MIP/electron)
8 front end channels
Development of an 8 channel 10 bit ADC
Signal to noise ratio ~19
Cross Talk < 1%

16. New readout : FLAME Yan Benhammou
FLAME: project of 16-channel readout ASIC in CMOS 130nm, front- end&ADC in each channel, fast serialization and data transmission, all functionalities in a single ASIC
FLAME prototype :
Prototype 8-channel FE+ADC ASIC
Prototype serializer ASIC
First tests are encouraging : FE ok, ADC ok, basic functionality of serializer are ok

17. BeamCal readout Yan Benhammou
Firstly, BeamCal is hit by beam halo (muons)
MIP deposition, low noise electronics
Clean environment
Good for calibration
~25ns later, BeamCal is hit by collision scattering
Large deposit energy
Physics readout
Dual slope integrator for calibration signal
Integrate baseline (negative gain)
Calibration halo signal is deposited and held
Switch to physics mode, process and digitize Vop
Then integrate calibration signal and digitize Voc

18. Radiation Damage Studies18 18

19. SLAC End-Station Test Beam (ESTB)
2 X0 pre-radiator; introduces a little divergence in shower
SLAC End-Station Test Beam (ESTB)
Sensor sample
Not shown: 4 X0 “post radiator” and 8 X0 “backstop”

20. Gallium Arsenide Sensor provided by Georgy Shelkov, JINR
Sn-doped Liquid-Encapsulated Czochralski fabrication
300 m thick 20 20

21. GaAs Charge Collection for 21 Mrad
Significant charge collection loss; leakage current low at -10oC but rises somewhat with temperature
21 Mrad Exposure
GaAs Sensor 21 21

22. Industrial Sapphire Sensor provided by Sergej Schuwalow
Fabricated by Crystal GmbH, Berlin
Layered Al-Pt-Au contact structure
Current low (< 10 nA) after irradiation 22 22

23. Sapphire Charge Collection for 300 Mrad
Low pre-irradiation charge-collection and
significant charge loss after irradiation; leakage current remains low.
Sensors via Sergej Schuwalow, DESY Zeuthen
500 m thick Al2O3
300 Mrad Exposure 23 23

24. Silicon Carbide Sensor provided by Bohumir Zatko, Bratislava
Schottky-barrier contacts mounted on 4H-SiC structure
Epitaxial (active) layer thickness 70 m 24 24

25. SiC Charge Collection for 77 Mrad
4H SiC Sensor
98C anneal
77 Mrad Exposure
Charge collection mostly above 50%; leakage current low 25 25

26. Silicon Diode Sensors Both n-type and p-type bulk sensors for
Float-zone crystal
Magnetic Czochralski crystal
Most notable variation is between n-type and p-type
Both develop significant leakage current, but p-type seems to maintain better charge collection (somewhat expected based on pure-EM irradiation studies from the 90s) 26 26

27. P Type Charge Collection after 270 Mrad
@600 V, ~20% charge collection loss (60C annealing)
270 Mrad Exposure
PF Si Diode Sensor 27 27

28. P Type I vs. Temperature; 270 Mrad
Current doubling for every 7oC expected for Si Diode
Qualitatively similar for all SI Diode sensors tested
Note: If damage is localized in BeamCal, may not lead to unmanageable power draw even after irradiation; this is under study (see FLUKA study below)
PF Si Diode Sensor
270 Mrad Exposure 28 28

29. P Type Charge Collection for 570 Mrad
Currents roughly x2 that for 270 Mrad
570 Mrad Exposure
PF Si Diode Sensor 29 29

30. N Type Charge Collection after 300 Mrad
@600 V, ~40% charge collection loss (58C annealing)
300 Mrad Exposure
NF Si Diode Sensor 30 30

31. N-Type LumiCal Prototype Fragment
After annealing, charge collection at 600V likely well above 50% after 300 Mrad exposure
Sensor via Sasha Borisov, Tel Aviv
300 Mrad Exposure
“LumiCal” N-Type Diode Sensor 31 31

32. BeamCal Neutrons from FLUKA32 32

33. BeamCal Simulation in FLUKA (Ben Smithers, SCIPP)
BeamCal absorbs about 10 TeV per crossing, resulting in electromagnetic doses as high as 100 Mrad/year
Associated neutrons can damage sensors and generate backgrounds in the central detector
GEANT not adequate for simulation of neutron field  implement FLUKA simulation
Design parameters from detailed baseline description (DBD)
Primaries sourced from single Guinea Pig simulation of e+- pairs associated with one bunch crossing
Proceeding into the simulations of the Beamcal, I would like to note that the geometric parameters of the beamcal were acquired from the ILC detailed baseline description. Additionally, we sourced our primaries from a Guinea Pig simulation of a bunch crossing.
After running the FLUKA simulations, I produced several cutouts of the resulting fluences of electrons and positrons, and neutrons, at various layers in the BeamCal. It gives a good idea of what is going on inside the BeamCal. I also used the raw data to find the layers of highest fluence. Layer 8 saw the highest electron positron fluence and 12 saw the highest neutron fluence.

34. Layer 2 Detector - Fluence
E+&E-
Neutrons

35. Layer 4 Detector - Fluence
E+&E-
Neutrons

36. Layer 6 Detector - Fluence
E+&E-
Neutrons

37. Layer 8 Detector - Fluence
E+&E-
Neutrons

38. Layer 10 Detector - Fluence
E+&E-
Neutrons

39. Layer 12 Detector - Fluence
Neutrons

40. Layer 14 Detector - Fluence
Neutrons

41. Layer 16 Detector - Fluence
Neutrons

42. Neutron Flux and BeamCal Sensor Radiation Damage
SLAC Experiment T506: prototype sensor
placed at shower max of electromagnetic
shower induced by tungsten  shower has
significant hadronic component
T506 exposures in the Mrad range
used to project effects of radiation damage
after multiple years of ILC running
Recent discovery: FLUKA simulations suggest
that damaging (non-ionizing) component of neutron
energy deposition, per Mrad (i.e., per MeV of dEdX
from e+-), is much higher in the BeamCal than at the T506 exposure point
If damage is dominated by neutron flux (?), will have important implications for BeamCal sensor choice, given varying degrees and types (charge loss, leakage current) of radiation damage observed in T506, which would thus represent a much shorter ILC running period
 Continuing to explore
SLAC e- beam
Sensor prototype 42 42

43. Summary
Need to do precision calorimetry in high-dose, high speed environment is driving a lot of R&D and design work
Work reasonably advanced, even at systems level
Significant use of test beams for prototype evaluation and radiation damage studies
Picture continuing to clarify (LHCal perhaps a bit behind) 43 43

44. Backup 44 44