Radiation damage to MPPCs by irradiation with protons

1. Radiation damage to MPPCs by irradiation with protons Toru Matsumura National Defense Academy in Japan for the KEK detector technology project June 29, 2007 (Kobe University) International Workshop on new photon-detectors (PD07)

2. Introduction • Multi-pixel Geiger-mode APD • a useful photon sensor for HEP, space science experiments and medical applications. For practical use of the sensor... radiation hardnessis one of important properties A program for radiation hardness tests of MPPCs @ KEK detector technology project • g-ray • Protons (main part of this talk) • Neutrons (short summary) • Carbons

3. Proton irradiation

4. Experiment for radiation hardness of MPPCs with a proton beam To investigate any changes on basic performance of the MPPCs due to radiation damage with protons. leakage current, gain, noise rate, etc. Purpose beam time 2007/4/22 8:00 - 2007/4/23 10:00 Collaborators: • NDAT.Matsumura, T.Shinkawa • Nara-WK.Miyabayashi • Osaka S.Shimizu, K.Horie • KyotoT.Tsunemi, A.Okamura, T.Hiraiwa • TitechM.Kuze, T.Matsubara • RCNP M.Yosoi, T.Sawada

5. MPPC samples • Two MPPC (400 pixels) samples • S10362-11-050C (ceramic package), Sample #20 • S10362-11-050C (ceramic package), Sample #21 (delivered in Feb. 2007) hole (to avoid radio-activation) 20×25 mm2 blue LED (for gain monitoring) MPPC

6. Beam conditions • AVF cyclotron @ RCNP, Osaka Univ. • Beam line ： W-hall H-course • Energy： proton 53.3 MeV • Beam size： 8 mm (H) × 6 mm (V) (flat distribution) • Large enough to cover the active area of the MPPCs (1 mm x 1 mm) • Uniformity of the beam intensity in the region of 4x4 mm2: < ~5% beam profile ~8 mm ~6 mm Experimental area ZnS sheet @ the exit port

7. Experimental setup Cu collimator 3.5 mmf 10mmt black sheet scintillator beam stopper (Pb) proton beam 53.3 MeV MPPC substrate beam pipe vacuum window (Al 0.1mm) 198 mm 80 mm • Beam intensity ... monitored with two plastic scintillates

8. Examples of radiation tolerances for HEP and space science ATLAS inner detector ... 3×1014 hadrons/cm2/10 year = ~ 104 hadrons/mm2/s General satellites ... ~ 10 Gy/year Irradiation item Total: 2.8×108protons/mm2 (= 42 Gy) • Sample #20 (higher-flux irradiation) • Beam flux 2.3×105 protons/mm2/s(130 Gy/h) • Irradiation time 10 minutes × 2 times = 20 minutes • Sample #21 (lower-flux irradiation) • Beam flux 3.0×104 protons/mm2/s(16 Gy/h) • Irradiation time 10 minutes× 3 times = 30 minutes Total: 5.4×107protons/mm2 (= 8.0 Gy)

9. Variation of the leakage current(higher flux irradiation) Sample #20 2.3×105 protons/mm2/s (130 Gy/h) 28.0±0.1℃ irradiation (10 min.) recovery measurement (2 h) leakage current (mA) recovery irradiation (10 min.) time (h) • The leakage current lineally increases with irradiated doses. • Annealing effects are seen. But the radiation damage is not completely • recovered within a few hour.

10. Variation of the leakage current(lower flux irradiation) Sample #21 3.0×104 protons/mm2/s (16Gy/h) irradiation(10 min.) irradiation(10 min.) irradiation(10 min.) recovery leakage current (mA) recovery measurement (1.4 h) measurement (1.3 h) recovery 27.4~27.8℃ 27.2~27.4℃ 27.0~27.2℃ time (h) • Similar tendency was observed as the higher-flux irradiation • except for increasing rates of the leakage current.

11. Sample #20(130Gy/h) Sample #21( 16Gy/h) Dose-rate dependence leakage current after 1 hour (mA) A smooth curve connected with the 3 points for the Sample #20 accumulated dose (Gy) • Increasing rate of the leakage current is almost same in the both fluxes. • 　　　　　→ No dose-rate dependence

12. MPPC The effect on radiation damage of MPPCs due to proton irradiation is at the same level as SiPM's. Sample #20(130Gy/h) Sample #21( 16Gy/h) Comparison with SiPMs M.Danilov arXiv:0704.3514v1 A test of radiation hardness of SiPMs has been reported. • 200 MeV protons (ITEP synchrotron) SiPM

13. I-V curves Sample #21 3.0×104 protons/mm2/s (16Gy/h) Sample #20 2.3×105 protons/mm2/s (130 Gy/h) 5.5 Gy leakage current (mA) leakage current (mA) 42 Gy 21 Gy 8.0 Gy 2.8 Gy V0 = 68.3 V V0 = 68.6 V 0 Gy 0 Gy bias voltage (-V) bias voltage (-V) • I-V curves become steeper as the irradiated dose increases.

14. Sample #20 (130 Gy/h) Sample #21 (16Gy/h) 0 Gy 0 Gy 21 Gy 2.8 Gy 42 Gy 5.5 Gy 8.0 Gy ADC distributions @ operating voltage noise rate 270 kHz noise rate 270 kHz 6.9 MHz >10 MHz >10 MHz >10 MHz gate width : 55 ns Noise-rate measurements were limited due to scaler performance >10 MHz • Photon-counting capability is lost due to baseline shifts and • noise pile-up after 21 Gy irradiation.

15. Sample #21 16 Gy/h Gain (106) 0 Gy (27.6℃) 2.8 Gy (27.4℃) 5.5 Gy (27.2℃) 8.0 Gy (27.0℃) operating voltage Vop = 69.58V bias voltage (-V) Gain curve For higher bias voltages, the gain measurement was difficult due to noise pile-up and baseline shift. No significant gain drop is found up to 8.0 Gy irradiation at the operating voltage (less than 5%).

16. Neutron irradiation

17. Neutron source MPPC holder • Fast neutron source reactor (YAYOI) • Continuum energy distribution 0.1 ~ 1 MeV (dominant component) Irradiated samples • MPPC S10362-11-100CK (100 pixels) • MPPC S10362-11-050CK (400 pixels) Radiation dose 8.3×104 ~ 3.3×105 neutrons/mm2, 1×108neutrons/mm2, 1×109neutrons/mm2, 1×1010neutrons/mm2 Collaborators: • Nara-W Univ.K.Miyabayashi, T.Hirai • Tokyo Univ. of scienceS. Tsunoda • KEK I. Nakamura, T. Nakadaira • Univ. of TokyoI. Saitoh, T. Nakagawa

18. I-V curves (preliminary) MPPC S10362-11-100CK (100 pixels) 8.3×104 neutrons/mm2 3.3×105 neutrons/mm2 1.0×108neutrons/mm2 Before irrad. After irrad. Before irrad. After irrad. Before irrad. After irrad. No significant change < 3.3×105 neutrons/mm2 I-V drastically change. Signal pulse is still there, but continuous pulse height. (No photon-counting capability) 108 ~ 109 neutrons/mm2 > 1.0×1010 neutrons/mm2 No signal

19. Comparison the damage among different radiation sources

20. proton irradiation 25℃ S10362-11-050C (400 pixels) 27 ℃ leakage current (mA) 60Co g-ray irradiation leakage current after 1 hour (mA) 25 ℃ T2K-11-100C (100 pixels) T.Matsubara (talk on this WS) irradiated dose (Gy) Damage effect ... 1~2 orders larger than g-ray irradiation

21. proton irradiation neutron irradiation S10362-11-050C (400 pixels) 2.3×105 protons/mm2/s (130 Gy/h) S10362-11-100CK (100 pixels) 4.2×105 neutrons/mm2/s 2.8×108 protons/mm2 1×108 neutrons/mm2 1.4×108 protons/mm2 leakage current (mA) leakage current (mA) V0 = 68.6 V before irradiation before irradiation bias voltage (-V) Ileak @ (Vop, 1.4x108 p/mm2) = 6.7 mA Ileak @ (Vop, 1.0x108 n/mm2) = 8.5 mA Damage effect ... almost same level

22. Summary • Tests of radiation damage of MPPCs were performed with proton and neutron sources. • Proton irradiation • Two samples of the MPPCs were irradiated with 53.3 MeV protons obtained at RCNP. Accumulated doses were 42 Gy and 8.0 Gy, respectively. Results: • Leakage current was linearly increased with the radiation dose independent of dose rates. The effect on radiation damage of MPPCs is at the same level as SiPMs. • Annealing effects are seen. But the damage is not completely recovered. • Photon-counting capability is lost due to baseline shifts and noise pile-up after 21 Gy irradiation. • No significant gain drop up to 8.0 Gy irradiation at the operating voltage.

23. Summary (cont.) • Neutron irradiation • Two type of MPPCs (100 pixels and 400 pixels) were irradiated with fast neutrons generated by the YAYOI reactor. Results: • No significant change was observed (< 3.3×105 n/mm2). • I-V curves drastically changed. Signal pulse was still there, butshowed continuous pulse height ( 108 ~109 n/mm2). • No signal observed ( > 1010 n/mm2). • Comparison the radiation damage among different radiation sources • 1~2 orders difference between protons and g-rays • same level for both protons and neutron irradiation.

24. Backup slides

25. Radiation damage • Two types of radiation damage • Bulk damage due to Non Ionizing Energy Loss (NIEL) • Surface damage due to Ionizing Energy Loss (IEL)(accumulation of positive in the oxide (SiO2) and the Si/SiO2 interface) M.Moll, PIXEL 2005 international workshop Neutrons ... Bulk damage is dominant Protons ... Bulk damage might be dominant ?? g-ray ... Surface damage would be dominant, but after ~1 hour annealing, bulk damage is dominant ??

26. Damage function Assumption: damage scales linearly with the amount of Non Ionizing Energy Loss (NIEL hypothesis) G.Lindstrom et al. NIM A426(1999)1-15 protons 53.3 MeV reactor neutrons expectation from the function protons / g-ray ~ 100 protons / neutrons ~ 2~10 60Co g-ray

27. Energy distribution of neutrons

28. MC simulation of a recoil-Si atom track with a primary energy of 50 keV

29. Co60 result ... T.Matsubara

30. -69.7 V -69.7 V -70.1 V -70.1 V -70.5 V -70.5 V ADC distributions (Sample #21) before irradiation after 2.8 Gy irradiation

31. 3.3×106 neutrons/mm2 I-V curves (preliminary) MPPC S10362-11-050CK (400 pixels) 8.3×106 neutrons/mm2 1.0×108 neutrons/mm2

32. ADC distributions after the 2.8 Gy irradiation 27.4℃ -69.5 V -69.7 V -69.9 V -70.1 V -70.3 V -70.5 V

33. sample #21, ADC distributions after 5.5 Gy irrad. 27.2℃ -69.5 V -69.7 V -69.9 V -70.1 V -70.3 V -70.5 V

34. ADC distributions after the 8.0 Gy irradiation -69.5 V -69.7 V -69.9 V -70.1 V -70.3 V -70.5 V

35. I-V curves (C12 6+ beam irradiation) 50C_1 Ｖ０＝70.59 Current (uA) 50C_2 Ｖ０＝69.55 100C_1 Ｖ０＝69.59 100C_1 Ｖ０＝69.48 50C not irradiated Ｖ０＝69.9 50C not irradiated Ｖ０＝69.57 • Note: • 50C • HPK S10362-11-100C(100 pixel) • 100C • HPK S10362-11-50C(400 pixel) Bias voltage(V) Temperature ：21±0.2 ℃ After 1.2 * 1010 (Carbon ion/mm2) irradiation Measurement were done on 2 month later of irradiation

36. Fit results 5 gaussian functions Vbias=-69.7V 2.8 Gy 5.5 Gy 8.0 Gy ADC (channel)

37. Absorption dose • stopping power of a 53.3 MeV proton in Si 9.381 MeV・cm2/g = 1.503x10-9 J・cm2/kg • absorption dose due to a proton in 1mm2 area 1.503x10-7 J/kg • absorption dose rate with 2x105/s proton beams 1.503x10-7 J/kg ・ 2.000x105 /s = 0.0301 J/kg/s = 108.2 Gy/h (=10.8 krad/h)