1. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Hiroyuki Sekiya ICRR, University of Tokyo Special Thanks T. Abe F. Tokanai, & T. Sumiyoshi Hamamatsu Photonics Review of photo-sensor R&D for future water Cherenkov detectors NNN10 Dec 15 2010 1

2. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Contents/Disclaimer 2 Many activities aiming for larger/lower cost/mass-production Quick review of only below technologies ◦Super Bi-Alkali /Ultra Bi-Alkali ◦Hybrid Photo-Detector ◦Gas Photo-Multiplier ◦Micro-PMT

3. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Do we need R&D? R3600-05 (The 20 inch PMT) is excellent. It provided reliable detectors and actual results. To keep the production quality of R3600- 05, continues order to Hamamatsu is the best way. We had better order 100,000 R3600-05s as soon as possible in order to get next generation water Cherenkov detectors within several years. 3

4. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Why do we R&D? Because we want better photon sensors with lower price in short delivery date! The key motivation is COST. ◦Some strategies to reduce cost  Fewer detector with better QE  Larger photo-coverage with cheaper sensors  Simple structure for short time/mass production  etc. 4

5. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Pessimistic conclusion Largest sensors cannot be applied to commercial market. Hamamatsu knows… Novel prize does not help their sales. Hamamatsu knows… After all, R3600-05 did not bring so much benefits to Hamamatsu. If we develop new sensors with them, cost/area may not decrease. It’s completely up to them. However, actually, they are always willing to develop new sensors with us and they are excellent. 5

6. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Super Bi-Alkali/Ultra Bi-Alkali 6

7. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Quantum efficiency Definition: SBA/UBA ν: frequency of the photon R: reflection coefficient k: total absorption coefficient Pν: excitation probability to vacuum level L: average deviating distance of the excited e - Ps: extraction probability from the surface vacuum level work function Fermi level valence band band gap electron affinity γ:hνγ:hν Reflection loss Loss in the PC Excitation efficiency Extraction efficiency SBA : reduction of the losses UBA : enhancement of the efficiencies 7

8. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama 5’’ SBA PMT is available → So far, UBA is available only for metal package PMTs “transfer” technology is required. ◦PC is made separately from the tube and assembled Not cheaper at all. 8

9. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Hybrid Photo-Detector(HPD) Hybrid car ◦Ex) Engine + Motor Hybrid photo sensor ◦Ex) Photo tube + Semiconductor  Hybrid gain: Bombardment + Avalanche TOYOTA PRIUS Hamamatsu HPDAPD 13’’ HPD Photo tube (cathode) Engine motor 9

10. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama HPD -operation principle- PMT Dynode APD ×10 7 × 4500@20kV Total hybrid gain ×10 5 × 30 HPD 10

11. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Concern? APD high dark current? P.E. collection efficiency reaches more than 95% (PMT: 70%) 20kV too high voltage? No increase in dark current after 1000h operation at 4mA Radiation hard. 11

12. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Better than PMTs This implies HPD is not cheaper than PMT. We should not require everything to realize low cost?? 12

13. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama More Hybrid may reduce total cost HPD+Electronics(A/D)+HV 13

14. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Performance of the Hybrid HPD Analogue output 1 p.e. 2 p.e. 0 p.e. 1p.e. 2 p.e. 3 p.e.? Digital output 14

15. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama 8’’ and 13’’ HPDs available in 2012 Hamamatsu will release in 2012 15

16. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Gas Photo-Multiplier(GPM) A kind of Hybrid detectors Electron multiplication by gaseous avalanche. If combined with photocathode, very large flat-panel detectors can be realized with much lower cost/area. A weak point → Strategy of “Do not require everything” F. Sauli Michigan University, Ann Arbor - May 23, 2002 LARGE MWPC 16

17. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama GPM –operation principle- Photocathode + Micro Pattern Gas Detectors Combination of MPGDs Multi-stage amplification Gas avalanche Total gain ×10 5 REFLECTIVE PC TRANSMISSIVE PC High resolution imaging Possible High QE photocathode 17

18. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Large Area MPGDs Very active R&D and actually in use! 100cmx30cm@CERN Mesh Rui de Oliveira MPGD2009 Micromegas with readout Kapton-GEM foil 150cmx50cm for T2K? TPC 18

19. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Large Area MPGDs in Japan Very active R&D and actually in use! μ-PIC with readout LCP-GEM foil 30cmx30cm for NEWAGE (Dark Matter Search) 31cmx28cm@Kyoto 19

20. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama MPGD2011 will be held in Kobe Aug 29 – Sep 1 2011 2 nd International workshop on MPGD followed by RD51 collaboration meeting Followed by RD51 collaboration meeting (Non-EU hosts for the first time) International organizing committee: A.Cardini (INFN Cagliari), K.Desch (U.Bonn), Th Geralis (Demokritos Athens), I.Giomataris (CEA Saclay), T.Kawamoto (ICEPP Tokyo), A.Ochi (Kobe Univ), V.Polychronakos (BNL), A.Sharma (CERN), S.Uno (KEK), A.White (U.Texas Arlington), J.Wotschack (CERN), Z.Zhao (USTC China) Local organizing committee: J.Haba (KEK), H.Hamagaki (CNS), T.Kawamoto (ICEPP), A.Ochi (Kobe Univ.), H.Sekiya (ICRR), A.Sugiyama (Saga Univ.), A.Taketani (RIKEN), T.Tamagawa (RIKEN), T.Tanimori (Kyoto Univ.), S.Uno (KEK) 20

21. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Feedback Problems in photon detection Ion and photon feedbacks Limit the stable high gain operation Many activities to overcome the feedbacks. ◦Gating ◦Ion defocusing by MHSP/COBRA A.Breskin TIPP09@Tsukuba １ ５ ◦Blind reflection A. Breskin et al., T. Sumiyoshi et al., 21

22. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama 2GEMs+μPIC with CsI PC 10cm x 10cm Possibility without Hamamatsu So far, tested with UV sensitive CsI ◦Low Ion feedback achieved! 10cm Sekiya et al Anode current PC current Deuteron Lump Ion Back Flow = Ic/Ia < 10 -3 @ gas gain 10 5 54mm TRANSMISSIVE CsI PC on MgF2 window REFLECTIVE CsI PC on Au coated LCP-GEM 22

23. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Imaging With solid UV scintillators Can be applied to LAr/LXe Star 犬 JINST 4 (2009) P11006 NIM (2010) doi:10.1016/j.nima.2010.06.114 23

24. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Hamamatsu’s GPM Bialkali PC + glass GEM(capillary plate) Prototype for R&D Pyrex glass GEM 24

25. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama TIPP09 in Tsukuba 25

26. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama QE in gas is lower –The weak point- Ne+CF 4 gas: 14% （ Max ＠ 350nm) Ar+CF 4 gas :12% （ Max ＠ 420nm) In vacuum ～ 20% In Ar+CF4 ～ 12% After evacuation, QE recovered to ~20%. Trans-missive Photocathode QE ~12% 26

27. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Long term stability QE maintains almost the same value after 581 days operations. Period (days) Relative gain 27

28. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Strong for Magnetic field Compensation coil for terrestrial B free! 28

29. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Make it larger Hamamatsu established the production of large Pyrex grass GEM thickness 300  m diameter at entrance 160  m diameter at center 124  m pitch 300  m Made by a new production Method: Sandblasting 10cm 29

30. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama By 2012, they will conclude Towards large flat panel photo-sensor 100mm square Pyrex glass GEM compared with H8500D These are assembled in a ceramic vessel? 30

31. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama μ-PMT If we don’t require the largeness Real low cost with real mass-production! MEMS (Micro Electro Mechanical Systems) technology realized μ-PMT → PMT?, silicon detector? No assemble, completely automated process Glass base Silicon base Glass base (window) Dynode by micro etching technology 13mm 10mm Photo cathode(SBA) 31

32. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama μ-PMT Prototype: 300 pieces on a 6’’ wafer Very uniform quality 20% Photo coverage possibility in future?? 2x2 sample Typical output signal of prototype 32

33. Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama Conclusion There are many activities that can be applied to next generation large water Cherenkov detector. Hybrid is also trend in photo-sensors. ◦The 20’’ PMT is still the candidate. ◦SBA technology is already taken into new photo- sensors. ◦HPD is the most plausible next generation candidate. ◦GPM can be a dark horse. ◦Post-next generation large sensor? 33