High Rate Photon Irradiation Test with an 8-Plane TRT Sector Prototype

1. High Rate Photon Irradiation Test with an 8-Plane TRT Sector Prototype J. Valls For the ATLAS-TRT Collaboration

2. Outline • Goals • FE Electronics • Experimental Setup • CERN X5-GIF • Weizmann Institute Irradiation Facility • Results • Occupancies and Rates • Occupancy Cross-talk • Hit Detection Efficiencies • Summary

3. Transition Radiation Tracker

4. Goals • Characterize and study the performance of near to final TRT FE electronics • Demonstrate basic operation of the detector at high counting rates • Two high rate irradiation tests planned • CERN X5 GIF 137Cs (662 keV photons), 0.5 MHz • Weizmann Istitute Irradiation Facility 60Co (1.1 and 1.3 MeV photons), 0.5-20 MHz

5. ASDBLR and DTMROC ASDBLR Amplifier Shaper Discriminator with Baseline Restoration DTMROC Digital Time Measurement and ReadOut Controller

6. Web Boards • Interface between signal from straws and FE electronics • Hold the HV decoupling capacitors, HV isolation resistors, and input protection circuit of FE chips Arc-shaped PC boards HV traces and petals Signal circuit

7. TRT Endcap Sector Prototype 12 DTMROC (24 ASDBLR) = 192 channels 8 planes x 24 straws = 192 straws Web boards

8. FE Characterization • Calibration of individual DTMROC threshold DACs relationship between DAC counts and voltages • Calibration of individual ASDBLR channels relationship between input signal amplitude and discriminator thresholds

9. DTMROC Calibrations V/DAC (low1) V/DAC (low0) V = f(DAC) V/DAC (high0) V/DAC (high1) ~5.3 mV/DAC

10. ASDBLR Calibrations • Measure S-curves for different input signals to extract gain and discriminator offsets • Threshold scans for a given input signal are characterized by S-curves

11. ASDBLR Calibrations Low Threshold High Threshold Gain Gain Offset Offset ~ 0.86 ± 0.09 mV/eV (gain) 122 ± 30 mV (offset) ~ 0.07 ± 0.01 mV/eV (gain) 99 ± 27 mV (offset)

12. Occ = f (DAC) Before calibration Occ = f (eV) After calibration ASDBLR Calibrations Vinp = 0.5 mV (~ 230 eV)

13. ASDBLR Threshold Spread Offset Threshold Spread w.r.t. Nominal Threshold (chip average) Nominal Threshold = 200 eV 12 ASDs shown All 192 channels  50 eV  50 eV

14. X5- GIF Facility Irradiator Radioactive 137Cs photon source (662 keV) X5 GIF Facility Test area with an adjustable high background flux of photons, simulating high rate background conditions Maximum Photon Flux ~ 107/s/cm2 Hit Probability per Photon (0.2 mm Al converter) ~ 0.5 - 1 % Charged Particle Rate 5x104 electrons/s/cm2 (LHC ~ 106 particles/s/cm2)

15. 60Co 60Co 1.1 MeV 1.3 MeV Sector Prototype 9.4 MHz Gamma Source 2.7 MHz 15.0 MHz 19.0 MHz 4.7 MHz 1.0 MHz Gamma Source Shielded (5 cm Lead) 0.5 MHz Weizmann Irradiation Area

16. Weizmann Irradiation Facility

17. Flex board WEB 1 WEB 2 Special web flap configuration with analog control Photon Source Straws sharing different web flaps (3 flaps per web) DTMROC (2 ASDBLRs) 16 straws ASDBLR (HV Group) Flex PCB

18. Occupancy Definitions • Straw Occupancy • Ratio of events with at least one hit over total number of events • Rates calculated from occupancies • Hits • LT hits: at least one low threshold bit set • LE hits: at least one leading edge • HT hits: at least one high threshold bit set (for either 1 or 3 beam crosses)

19. Occupancies (%) 3 BC Rates (MHz) Noise Rate Noise Occupancy 169  221 kHz 1.3  1.7 % 250 eV 250 eV LE LT Noise Occupancies and Rates X5 GIF 1.0  1.1 % (3 BC) 130  143 kHz(3 BC) (200 eV)

20. Rates

21. HT LE LT Energy Spectrum Shapes Low Threshold Occupancies High Threshold Occupancies • Harder energy spectrum at low rates • Softer at high rates 1.0 MHz • Low threshold occupancies higher at low thresholds for low rates • Flat at high rates 15.0 MHz

22. 60Co Gamma Source 15.0 MHz 19.0 MHz Irradiation Area 60Co 9.4 MHz 4.7 MHz 2.7 MHz Gamma Source Shielded (5 cm Lead) High Rates (softer energy spectrum) 1.0 MHz Low Rates (harder energy spectrum) 0.5 MHz

23. Test-Beam Energy Spectrums 20 GeV electrons 20 GeV pions

24. Energy Spectrum Shapes 0.5 MHz 1.0 MHz Low Threshold 250 eV 2.7 MHz 4.7 MHz

25. Energy Spectrum Shapes 0.5 MHz 1.0 MHz Low Threshold 300 eV 2.7 MHz 4.7 MHz

26. Cross-Talk • Conductive coupling in the straws which share the same decoupling capacitor • Parasitic capacitive coupling at the end of the straws Ccoupl Cblock Riso Signal return HV + filter • Internal channel-to-channel cross-talk of the analog ASDBLR chip • Cross-talk through connecting traces on the flex-rigid boards and web board

27. High Threshold Hit Required on a Trigger Straw Straws sharing the same HV group Straws sharing the same web flap Occupancy Cross-Talk

28. ASDBLR HVgroup Web flap Away straws Occupancy Cross-Talk 5 keV 7 keV 2.7–2.1 increase 3.1–2.9 increase 11 keV 4.0–2.9 increase Background Rate 0.5 MHz

29. Occupancy Cross-Talk 5 keV 3 keV 2.0–1.8 increase Background Rate 1.0 MHz 2.0–1.4 increase 9 keV 2.4–1.3 increase 11 keV 2.6–1.3 increase

30. Occupancy Cross-Talk 3 keV 5 keV 1.3–1.2 increase Background Rate 2.7 MHz 1.4 increase 9 keV 11 keV 1.6–1.1 increase 1.6–1.1 increase

31. Occupancy Cross-Talk 400 eV 250 eV 0.5 MHz 170-200% (250 eV) 140-190% (400 eV) 250 eV 400 eV 2.7 MHz 30-60% (250 eV) 20-50% (400 eV)

32. ASDBLR HVgroup Web flap HT Occupancy Cross-Talk No Cross-Talk in High Threshold Occupancies

33. Use calibrated internal test pulse signals 15 DAC  600 eV (50% Occ) 21 DAC  1 keV (50% Occ) Test pulse signals adjusted in time to arrive always at the same position (middle BC) Hit efficiency (per channel): fraction of events with a LE hit in a selected time window over total number of events 3 bins Hit Detection Efficiencies No Irradiation

34. No Irradiation 1.0 MHz 0.5 MHz 9.4 MHz 2.7 MHz 4.7 MHz 19.0 MHz 15.0 MHz Time Over Threshold Low Threshold 250 eV

35. 1.0 MHz 0.5 MHz 2.7 MHz 9.4 MHz 4.7 MHz 19.0 MHz Time Over Threshold Low Threshold 600 eV

36. Time Distribution of LEs 15.0 MHz 1.0 MHz 4.7 MHz 19.0 MHz 2.7 MHz 9.4 MHz Low Threshold = 250 eV Loss of width from undershoot and pile-up

37. 250 eV 300 eV 400 eV 1000 eV Time Occupancies • Time occupancies are defined as the ratio between time occupied by LE’s in 3 BC’s over total time Low Threshold 15.0 MHz 1.0 MHz

38. 250 eV 300 eV 400 eV 600 eV Hit Detection Efficiencies Low Threshold Test Pulse 600 eV Test Pulse 1000 eV

39. Hit Detection Efficiencies Lab Measurements 18.6 ns, 2.8 keV 37.2 ns, 3.9 keV 55.8 ns, 3.9 keV Input Test Pulse 600 eV Test Beam These Measurements

40. Hit Detection Efficiencies Test-Beam Drift-Time “2.5 ” Efficiency Input Test Pulse 1000 eV

41. Hit Efficiencies (Summary)

42. Noise ocupancies (250 eV, middle BC) 0.5% 170 kHz Occupancies under irradiation (250 eV, middle BC) 3.6% 1.4 MHz (data)  0.5 MHz (monitor straw) 13.0%  5.2 MHz (data)  4.7 MHz (monitor straw) 26.3%  10.5 MHz (data)  15.0 MHz (monitor straw) Summary (part 1/3) • Background energy shapes similar to those from past electron test-beams for most of the data. Harder energy spectrums for data taken at low rates (0.5-1.0 MHz)

43. Summary (2/3) • Hit detection efficiencies • Up to 5 MHz  > 90% • Rapid decrease for > 5 MHz • Occupancy cross-talk • Confirm results from previous X5 GIF test • Low threshold occupancies (250 eV) 0.5 MHz  170% - 200% for 5 - 11 keV signals 1.0 MHz  100% - 160% for 5 - 11 keV signals 2.7 MHz  30% - 60% for 5 - 11 keV signals • High threshold occupancies slightly affected (<10%)

44. Thanks….. Weizmann Institute Of Science • George Mikenberg • Meir Shoa • Staff irradiation unit • Gideon Ben Moshe • Shaul Ovadya