Intensive Study on CsI Crystal Readout by Hamamatsu MPPC

This study presents detailed analysis of a 3x3x18 cm³ CsI crystal readout using a Hamamatsu large area MPPC. Various tests were conducted on the MPPC and electronics setup, including laser pulsing and signal reduction. The results show improved time resolution and slewing correction, enhancing the overall performance of the system.

• CsI Crystal
• Hamamatsu MPPC
• Electronics Test
• Time Resolution
• Laser Pulsing

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1. Intensive study on a 3x3x18 cm3 CsI crystal readout by an Hamamatsu large area MPPC Ivano Sarra on behalf of the Frascati Group Mu2e Italian Meeting 12 February 2015 (happy birthday Ivano)

2. Test MPPC and Electronics (~50 ps FWHM/2.35 resolution) We pulsed the MPPC with a Hamamatsu blue laser (3x3 mm2 each) The readout is the sum of 16 UV-SPL MPPC Array SPL MPPC: Preamplifier: very low input impedance 200 MHz BW 2 V dynamic Gain 8 one single HV Sum of the 16 MPPC 2

3. Test MPPC, the Electronics and the FADC Analog Signals have been acquired with a 1 GHz / 10 bits Flash ADC by CAEN It has 1 Vpp dynamic range and 10 bits We decided to reduce the MPPC signal of a factor 0.4 to use all the dynamic range of the preamplifier (Gain = 8 3) 3

4. MPPC with LASER: peak fit technique 8884 / 12 8884 / 12 1.617e+04 / 43 1.617e+04 / 43 2c Prob p0 p1 p1 2c Prob p0 2c 2c Prob Prob / ndf / ndf 0 0 / ndf / ndf 0 0 0.001942 97.33 0.002394 3.321 0.002394 3.321 0.001942 97.33 1.151 1.151 Norm Norm 4189 4189 0.008672 180.5 0.008672 180.5 m m 0.002104 0.5444 0.4975 546.5 0.4975 546.5 0.002104 0.5444 p2 p3 p3 p2 0.009209 12.94 0.009209 12.94 s s 800 500 700 600 400 500 300 400 200 300 200 100 100 0 0 - 100 4 0 100 200 300 400 500 80 85 90 95 100 105 110

5. Time resolution Peak Time(MPPC) Peak Time(laser trigger) N. Entries / 100 ps 1400 Entries Entries 9639 9639 1200 18.8 18.8 Constant Constant 1454 1454 1000 Mean Mean 83.1 83.1 0.0 0.0 800 Sigma Sigma 0.2574 0.2574 0.0022 0.0022 600 400 200 0 81 82 83 84 85 86 5 Time [ns]

6. Slewing Correction Time [ns] 88 Entries Mean Mean y RMS RMS y p0 p1 Entries Mean Mean y RMS RMS y p0 p1 p2 p2 9639 986.9 83.1 125.6 0.2638 82.48 0.000788 1.416e 1.416e 9639 986.9 83.1 125.6 0.2638 82.48 0.000788 86 84 82 - - - - 06 06 80 78 76 600 800 1000 1200 1400 1600 Adc counts [pC] 6

7. Time resolution after slewing Peak Time(MPPC) Peak Time(laser trigger) ~ 75 ps of resolution N. Entries / 100 ps 500 Entries Entries 9639 9639 Constant Constant 492.7 492.7 6.4 6.4 400 - - Mean Mean 0.002662 0.002662 0.000833 0.000833 300 Sigma Sigma 0.07682 0.07682 0.00066 0.00066 200 100 7 0 0.6 - 0.4 - 0.2 - 0 0.2 0.4 0.6 0.8 1 Time [ns]

8. Time resolution: Vbias scan 120 Time resolution [ps] 100 66.7 V 66.1 V 66.4 V 67 V 80 60 40 20 0 8 400 500 600 700 800 900 1000 Adc counts [pC]

9. We will perform rate studies TO BE COMPLETED 9

10. Test CsI, MPPC and Electronics with Na22 source We started using a Na22 source(2 back to back @ 0.511 MeV) Trigger given by a finger 3mm above the source and the CsI crystal. Source placed in the middle of the CsI crystal (30x30x180 mm2) Crystal wrapped with Teflon (3 round ~ 75 um thickness) Still used a factor 0.4 of reduction Gain Amplifier ~ 3 10

11. No optical grease Rhodorsil Paste 7 Entries / 1pC Entries / 1pC 300 300 Entries Entries 4457 4457 Entries Entries 4014 4014 250 6.0 6.0 Constant Constant 304.9 304.9 6.4 6.4 Constant Constant 317.4 317.4 250 Mean Mean 9.802 9.802 0.099 0.099 Mean Mean 6.944 6.944 0.087 0.087 200 200 Sigma Sigma 5.26 5.26 0.07 0.07 Sigma Sigma 4.645 4.645 0.059 0.059 150 150 100 100 50 50 0 0 10 - - 10 - - 5 0 5 10 15 20 25 30 35 40 5 0 5 10 15 20 25 30 35 40 Adc counts [pC] Adc counts [pC] ~ 22 p.e./MeV ~ 31 p.e./MeV 11

12. Noise term Entries / 1pC ENE: ~ 270 keV no grease ~ 190 keV with grease 400 Entries Entries 3901 3901 8.8 8.8 Constant Constant 408.4 408.4 300 Mean Mean 0.3774 0.3774 0.0625 0.0625 Sigma Sigma 3.704 3.704 0.056 0.056 200 100 0 10 - - 5 0 5 10 15 20 25 30 ADC counts [pC] 12

13. Test CsI, MPPC and Electronics with Cosmic rays Trigger given by the coincidence of two scintillator fingers one above and the other below the CsI crystal. Fingers readout by SiPm 4x4 mm2 of SensL Crystal wrapped with Teflon (3 round ~ 75 um) Still used a factor 0.4 of reduction Gain Amplifier ~ 3 MPPC CsI crystal Top View 15 1x1 cm2

14. Imagine from the scope 16

15. Fit Technique 1) We fit the shape with a pol7 function 2) We set a threshold value (i.e. 40 mV) 3) We extract the inverse value of the pol7 function at the threshold setted 442.9 / 12 442.9 / 12 2c Prob Prob 2c / ndf / ndf 0 0 1.462 1.462 Constant Constant 487.3 487.3 0.009892 87.04 0.009892 87.04 Mean Mean 0.009667 2.825 0.009667 2.825 Sigma Sigma 385.4 / 12 385.4 / 12 2c 2c Prob Prob / ndf / ndf 0 0 1.496 490.7 1.496 490.7 Constant Constant 0.009561 74.51 0.009561 74.51 Mean Mean 0.009259 2.68 0.009259 2.68 Sigma Sigma 160 500 500 2c 2c / ndf / ndf 87.5 / 68 87.5 / 68 Prob Prob 0.05582 0.05582 140 mV 1.417e+04 1.417e+04 p0 p0 2.23e+05 2.23e+05 400 400 p1 p1 - - 946.8 946.8 1.426e+04 1.426e+04 120 26.86 26.86 p2 p2 385.2 385.2 p3 p3 - - 0.4196 0.4196 5.711 5.711 100 0.003896 0.003896 p4 p4 0.05028 0.05028 300 300 p5 p5 - - 2.152e 2.152e 05 - 05 - 0.0002633 0.0002633 - - 6.546e 07 6.546e 07 08 - 08 - p6 p6 7.6e 7.6e 80 p7 p7 - - - - 8.461e 10 8.461e 10 11 - 11 - 9.336e 9.336e 200 200 60 40 100 100 20 0 0 0 Finger top Finger bottom CsI + MPPC 17 60 65 70 75 80 85 90 75 80 85 90 95 100 50 100 150 200 250 300 ns

16. No optical grease Rhodorsil Paste 7 100 N. Entries / 20 pC N. Entries / 20 pC N. Entries / 1 p N. Entries / 1 p 60 5 90 4 Entries Entries 887 887 Entries Entries 1125 1125 Entries 887 Entries 887 Entries 1125 Entries 1125 343.1 343.1 80 3.5 Mean Mean c c 2 2 / ndf / ndf 86.03 / 66 86.03 / 66 80 RMS RMS Mean 4.74 Mean 4.74 167.8 167.8 Mean 4.768 Mean 4.768 4 70 3 Prob Prob 0.04951 0.04951 c c 2 2 / ndf / ndf 5.877 / 7 5.877 / 7 RMS 5.77 RMS 5.77 RMS 7.981 RMS 7.981 0.5542 0.5542 Prob Prob 60 Constant Constant 461.5 461.5 25.6 25.6 2.5 Constant Constant 538.1 538.1 38.4 38.4 3 MPV MPV 440.7 440.7 2.8 2.8 50 298.6 298.6 2.6 2.6 MPV MPV 2 Sigma Sigma Sigma Sigma 22.11 22.11 1.85 1.85 36.22 36.22 1.68 1.68 40 40 2 1.5 30 1 20 20 1 0.5 10 0 0 0 0 30 - 20 - 10 - 30 - 20 - 10 - 400 0 10 20 30 0 200 600 0 10 800 1000 20 30 0 500 1000 1500 2000 Charge [pC] Charge [pC] Charge [pC] Charge [pC] 18 ~ 22 MeV ~ 23 MeV

17. Cosmic with Monte Carlo Giani has produced a MC using a setup similar to the real one: - He selected events in 1 cm2 area above and below the crystal; - Photo statistic and noise still not included. Without experimental effects With Experimental effects 200 Entries / 0.5 MeV Entries Mean RMS / ndf c Prob Constant MPV Entries Mean RMS / ndf c Prob Constant MPV Sigma Sigma 10000 23.89 7.211 40.1 / 55 0.9343 17.6 991.7 19.7 2.341 2.341 10000 23.89 7.211 40.1 / 55 0.9343 17.6 991.7 19.7 180 160 2 2 140 120 0.1 0.1 100 0.071 0.071 80 60 40 20 19 0 0 10 20 30 40 50 60 70 Deposited Energy [MeV]

18. No optical grease Trigger time resolution N. Entries / 200 ps N. Entries / 200 ps 140 Entries Entries 391 391 391 391 Entries Entries 35 Constant Constant 146.4 146.4 9.5 9.5 2.15 2.15 32.25 32.25 Constant Constant 120 30 - - Mean Mean 6.35 6.35 0.01 0.01 - - 2.218 2.218 0.053 0.053 Mean Mean Sigma Sigma 100 0.2086 0.2086 0.0087 0.0087 0.0451 0.0451 Sigma Sigma 0.9288 0.9288 25 80 20 MPPC and Fingers Half-sum Time Difference ~ 930 ps Finger0 and Fingers Half-sum Time Difference ~ 210 ps 60 15 40 10 20 5 0 0 10 - - - - - - - - 5 0 5 10 15 8 7 6 5 4 3 20 Time [ns] Time [ns]

19. No optical grease Slewing Correction p0/sqrt(x)+p1 15 20 390 390 Entries Entries Entries Entries 391 391 10 ns 315.8 315.8 Mean Mean y Mean y Mean 15 Mean 7.347 Mean 7.347 - - 2.178 2.178 5 Mean y Mean y - - 12.69 12.69 53.47 0.9425 0.04 0.04 53.47 0.9425 RMS RMS RMS y RMS y 10 RMS 3.426 RMS 3.426 0 p0 p0 223.9 223.9 0.6 0.6 RMS y 0.4053 RMS y 0.4053 p1 p1 5 - - 15.24 15.24 - 5 0 - 10 - 5 - 15 - 10 200 300 400 500 0 5 10 15 20 21 pC

20. No optical grease Rhodorsil Paste 7 90 N. Entries / 200 ps N. Entries / 200 ps 60 80 Entries Entries 391 391 Entries Entries 461 461 c c 2 2 / ndf / ndf 16.64 / 11 16.64 / 11 2c 2c / ndf / ndf 12.62 / 9 12.62 / 9 50 70 Prob Prob 0.1191 0.1191 Prob Prob 0.1806 0.1806 60 3.79 3.79 40 Constant Constant 56.56 56.56 4.55 4.55 Constant Constant 78.64 78.64 50 Mean Mean 0.4004 0.4004 0.0289 0.0289 - - Mean Mean 0.02506 0.02506 0.02225 0.02225 30 Sigma Sigma 0.5173 0.5173 0.0228 0.0228 40 Sigma Sigma 0.4523 0.4523 0.0159 0.0159 30 20 20 10 10 0 0 - - - - 4 2 0 2 4 6 8 4 2 0 2 4 6 8 10 Time [ns] Time [ns] MPPC and Fingers Half-sum Time Difference ~ 450 ps ~ 420 ps after trigger correction MPPC and Fingers Half-sum Time Difference ~ 520 ps ~ 500 ps after trigger correction 22

21. Stability of the system Temperature of the clean room 22.5 0.5 C 1 event ~ 5-6 minutes 4 days of run HV = 67V (Vop) with a stability of <10 mV Adc Count [pC] 350 300 Entries Mean Mean y RMS RMS y / ndf c Prob p0 p1 p1 Entries Mean Mean y RMS RMS y / ndf c Prob p0 642 642 250 442.4 334.9 254.6 82.04 82.04 442.4 334.9 254.6 200 150 2 2 23.91 / 22 0.352 333.6 0.012322 0.012322 23.91 / 22 0.352 333.6 100 6.3 6.3 - - 0.006347 0.006347 23 50 0 0 100 200 300 400 500 600 700 800 900 Event Number

22. Summary We have tested the performances of a CsI crystal readout by the new UV extended MPPCs from Hamamatsu: 1) The preamplifier and HV stage gave satisfactory results in term of stability, noise and time resolution; 2) The measures with and without optical grease gave encouraging results. 3) The number of photoelectrons per MeV and the timing resolution measured, as response to the MIP, meet the goals of the experiment; 10 monolithic MPPCs will be delivered in the beginning of March The final electronics will be ready for the end of February The test beam at BTF is scheduled from the 6 up to the 12 of April to test a matrix of 9 CsI crystals (3x3x18 cm3 each). 24

23. TANK YOU FOR THE ATTENTION 25