1. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Development of High Performance Avalanche Photodiodes and Dedicated Analog Systems for HXI/SGD Detectors onboard the Astro-H mission T.Saito, M.Yoshino, H.Mizoma, T.Nakamori, J.Kataoka (Waseda U.), M.Ohno, K.Goto, Y.Hanabata, H.Takahashi, Y.Fukazawa (Hiroshima U.), M.Sasano, S.Torii, H.Uchiyama, K.Nakazawa, K.Makishima (U.Tokyo), S.Watanabe, M.Kokubun, T.Takahashi, K. Mori (ISAS/JAXA), H.Tajima (Nagoya U.) and Astro-H HXI/SGD team

2. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Outline 2 1.Introduction 2.Development of APD 3.Development of analog systems 4.Summary -CSA for Astro-H -Analog amplifier -Whole system performance BGO APD CSA ADC Analog amplifier Digital filter

3. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Astro-H Instruments Astro-H is the 6 th satellite of Japanese X-ray observatory series HXI/SGD detectors employ BGO active shields 3 to be launched in 2014 with the H-IIA rocket wide band observation : 0.3 – 600 keV(four instruments) we are developing readout sensor (APD) and dedicated analog system for BGO active shields.

4. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 BGO Active Shield 4 BGO APD reduce backgrounds by anti-coincidence technique The main detector is surrounded by BGO scintillators Avalanche Photodiodes (APD) readout generating active veto signals to reject cosmic-ray particles and gamma-ray backgrounds BGO HXI Main camera depth Electric field Gain photon

5. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 5 BGO APD CSA ADC Analog amplifier Digital filter

6. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 － Thermal test (silicone or epoxy resin for APD window) － Radiation tolerance test ( 60 Co, the total dose : 10krad) － pre-FM APD acceptance test (evaluate 20 pre-FM APD) APD for Astro-H 6 Development of pre-Flight Model (pre-FM) APD Screening test EM shield － Window material : silicone resin － Active area : 10 x 10 mm 2 － Capacitance : ～ 400 pF (gain : 50, inc. dedicated cables) － Dark current : < 0.4 nA (gain : 50 @ － 15 deg) Flight Model APD screening test ( ～ Apr, 2012)

7. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Elapsed time [hour] Temperature [deg] 1h dwell 20 deg/h 1 cycle (10h) Thermal test 7 silicone or epoxy resin for APD window severe temperature environment just after the launch thermal cycle test silicone epoxy The number of the Cycle Relative light intensity [%] 14% Down 50% Down APD and BGO come unglued? couple each APD with BGO using a space grade silicone adhesive We selected the silicone resin for the APD window Comparison of pulse heights

8. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Radiation tolerance test 8 The number of APD Difference between V b [V] Difference between V b before and after irradiation Breakdown voltage V b did not substantially decrease 60 Co irradiation (total dose : 10 krad, ～ 1krad/year) Although I d increase 6 times, test pulse width increase only 3 keV! Breakdown voltage V b decrease? Deteriorate I d and noise performance? Total dose [krad] Dark current [nA] Test pulse width [keV] (FWHM) 00.310.6 101.913.2 Performance before and after irradiation Because capacitive noise is dominant @ － 15deg Test pulse width evaluated by BGO (1x1x1 cm 3 ) + pre-FM APD

9. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Different changes pre-FM APD acceptance test 9 Establish how to screen FM APD dark current I d and operation voltage V r at gain 50 evaluate 20 pre-FM APDs at three temperatures around – 15 degree Temperature [deg] Dark current I d [nA] Temperature [deg] Operation voltage V r (gain : 50) [V] Bad (>0.4 nA) high V r We will do FM APD screening test in a similar way

10. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 APD Dark current 10 Constitution of APD dark current I d I d = I ds + M * I db I ds : surface current I db : bulk current Leakage path of surface current Bulk current p n π n Temperature Current IdId I ds M * I db source ① Ratio between I ds and I db is possibly different ② At in-orbit temperature I db is dominant because of avalanche gain ③ If APD has higher I db, this APD show different I d changes

11. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 11 BGO APD CSA ADC Analog amplifier Digital filter

12. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 CSA for Astro-H 12 APD capacitance including cables is ～ 400 pF. Capacitive noise is dominant @ － 15deg. DIP type hybrid IC CAN type hybrid IC CSA-Hybrid IC evaluation circuit Charge sensitive amplifier (CSA) specialized for Astro-H (FM type) Astro-H CSA need good noise performance

13. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Performance of CSA 13 shaper Test pulse CSA Detector capacitance 0 〜 1000 pF APD + cables capacitance 2000 eV 9.8 eV/pF 400 pF (APD + cables) testpulse width : 6 keV (FWHM, Si 60keV) 8x8x4 cm 3 BGO testpulse width : 21.7 keV (FWHM) Noise performance Convert into active shield performance Detector capacitance [pF] Testpulse width[eV (FWHM, Si 60keV)] Evaluation of CSA assuming APD capacitance ～ 400 pF good capacitive gradient : 9.8 eV/pF

14. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 14 BGO APD CSA ADC Analog amplifier Digital filter single-stage differential and integrating circuit

15. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 15 Analog amplifier Optimize the best “integrating time constants” Testpulse width[keV (FWHM, BGO 662keV)] Integration time constant [us] \ count ADC channel [ch] Testpulse 137 Cs “the expended time of output veto signal to the main detector” < 5  s peaking time adjusted by differential filter (τ > 1.3  s) Without differential filter employ integrating time constants 1.0 – 1.2  s

16. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 16 BGO APD CSA ADC Digital filter Analog amplifier

17. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Whole system performance 17 Performance of active shield system circuit digital filter : Ohno, M. et al. (2011) HSTD-8 Testpulse width[keV (FWHM, BGO 662keV)] Integrating time constant [us] Filled marker using analog & digital filter better than ready-made analog shaper (ORTEC570 & CP4417) Ready-made shaper using integrating time constants 1.0 – 1.2  s better 1.0  s (only analog) 1.1  s (only analog) 1.2  s (only analog) 1.0  s (analog & digital) 1.1  s (analog & digital) 1.2  s (analog & digital) CP4417(1.0  s) ORTEC570(1.0  s) Analog & digital filter

18. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Summary 18 APD Thermal test employ silicone resin for APD window Radiation tolerance test passed ( 60 Co 10 krad) pre-FM APD acceptance test establish how to screen FM APD CSA good capacitive gradient : 9.8 eV/pF 400 pF (APD + cables) testpulth width : 6 keV (FWHM, Si 60keV) Analog amplifier employ integrating time constants 1.0 – 1.2  s Whole system performance achieve a good noise performance (better than ready-made analog shaper) Future works large pulse response test (proton, Fe), end-to-end test

19. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 19 Backup slides

20. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 : time constant Analog noise 20 total noise of analog circuit Capacitive noise Dark current noise : surface current : bulk current : gain of APD: capacitance of APD

21. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Dark current(-20 ～ +25 deg) 21 Dark current [nA] Temperature [deg]

22. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 CSA Performance inc. Ref. 22 shaper Test pulse CSA Detector capacitance 0 〜 1000 pF APD + cables capacitance 2000 eV 9.8 eV/pF 400 pF (APD + cables) testpulse width : 6 keV (FWHM, Si 60keV) 8x8x4 cm 3 BGO testpulse width : 21.7 keV (FWHM) Noise performance Convert into active shield performance Detector capacitance [pF] Testpulse width[eV (FWHM, Si 60keV)] Evaluation of CSA assuming APD capacitance ～ 400 pF － : Astro-H CSA － : Reference

23. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 23 APMU analog BBM board Analog amp. board APMU analog BBM board

24. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 24 時定数 [us] R1[kΩ]R2[kΩ]R3[kΩ]C1[pF]Gain(R2 / R1)offset[V] 1.05.11021001.960.9 1.15.61121001.960.9 1.25.11021201.960.9 1.325.61121201.960.9 1.55.11021501.960.9 1.65.61121501.960.9 1.85.11021801.960.9 1.985.61121801.960.9 R1 R2 R3 C1C1 5V Parameter No using differential filter

25. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 25 ＊ testpulse width (3xFWHM, BGO 662keV) typeB 8×8×4 Without differential filter

26. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 twin-T filter 26 twin-T filter for the better analog filter performance equivalent nine-stage integrating circuit twin-T filter must use a differential filter for peaking time < 5  s C noise performance is shown in the next slide C R 4 R 3 R 4 5 C 2 1

27. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 Performance inc. twin-T 27 Performance of active shield system circuit digital filter : Ohno, M. et al. HSTD-8 Testpulse width[keV (FWHM, BGO 662keV)] Integrating time constant [us] Filled marker using digital filter better than commercial analog shaper(ORTEC570 & CP4417) Commercial shaper Twin-T using integrating time constants 1.0 – 1.2  s better

28. HSTD-8, Academia Sinica, Taipei Taiwan, 8 th December, 2011 APD window 28 APD Window + BGO APD & BGO adhered by DC93-500