1. 1 Development of a Large Area Photodetector with a Fast Phosphor Anode Toru Iijima Kobayashi-Maskawa Institute Nagoya University Open Meeting for the Hyper-Kamiokande Project August 21-23 @ Kavli IPMU Work supported by grant-in-aid from MEXT; 18654043 ( 萌芽研究, 2006-2007), 23340065 （基盤 B, 2011-2013) 2012/08/23

2. Development of Photon Sensors at N-lab. 2 2012/08/23 HAPDMCP-PMTG-APD(MPPC)PMT w/ scint. Detector Development Lab. For Belle II PID Aerogel radiator HAPD MCP-PMT

3. Motivation Physics goal of the next generation water Cherenkov detector:  Search for proton decays ( t > 10 35 yrs).  Precision neutrino oscillation & CPV measurements.  Neutrino astronomy. It requires cost effective method to produce large number of photosensors w/ large area. Existing 20’ PMT technology is fine, but, still important to pursue other possibility for photosensor;  Good performance  Reliable/Robust  Cheap ! 3 2012/08/23

4. Concept: “Photo-multiplier” w/ phospher 2012/08/23 4 Incident photon Photo cahode Sensor scintillator Light guide Al back Photoelectron Multiplier Simple structure: Active component is ouside the vacuum and is relatively cheap. Multiplier/sensor are produced separately. Potential merits in yield & cost MPPC/ Si-PM

5. Similar Development The idea using is not new, and already used for DUMAND SMART and Lake Baikal QUASAR PMT. 5 2012/08/23 Quasar-370LSO w/ LSO crystal YSO(Y 2 SiO 5 :Ce) YAP(YALO 3 :Ce) SBO(ScB 3 :Ce) LSO(Lu 2 SIO 5 :Ce) More recent development at CERN (X-HPD) See B. Lubsandorzhiev, NIM A610, 68 (2009) and reference therein A. Braem, C. Joram, J.Suginot, P. Solevi, A-G. Dehaine, NIM A610 (2009) 61.

6. Faster Phosphor ? 6 2012/08/23 Q: What is this ? A: A kind of … Decay time (90  10%) = 500ps (typ.) Emission peak = 400nm ZnO (Ga) Poster by B. Lubsandorzhiev E.D. Bourett-Courchesne et al. NIMA ZnO (In) P.J. Simpson et al. NIM A505, 82 (2003)

7. Photo-gain.vs. Efficiency Assumption Multiplier  =100% Sensor PDE=30% V th =1.5 p.e. 80.8%@G=2 99.5%@G=5 2012/08/23 7 QE: QE of the 1 st photocathode HV: Acceleration voltage [kV] E 0 : Energy loss in Al-back [keV] Y: Light yield of scinti. [counts/MeV]  : Light transport efficiency Photo Gain Present result: G~3 G: Photo-gain N in N out P: Probability to detect a photoelectron from 1 st photocathode) PDE (Photodetection efficiecny) = QE (1 st stage) x P P

8. 8-inch sample 5 samples have been produced w/ the same bulb as used for HAPD Readout by ¾-in. PMT (H6533) 8 2012/08/23 Sensor (H6533) Multiplier photocathode φ ： 8 イン チ 光電面 光検出器 電場 QE ~ 20% @ 400nm

9. Bench Test H6533 N out Output photons H6533 Reference PMT 404nm 2012/08/23 9 Setup Photo-gain measurement Pulsed laser (HPK, PLP-02) N in Incident photons Ratio of H6533 output: Q (w/ multiplier) Q (w/o multiplier) G =

10. Photo-gain of the multiplier 2012/08/23 10 w/o multiplier - ped = 216 w/o multiplier - ped = 222 HV (kV) Photo-gain G = 1.4 w/ 12kV & 10mm gap. Saturation due to limited thickness of J9753 H6533 Gap bet. output window – H6533 Deterioration of P.H. resolution due to multiplier

11. Photo-gain w/ light guide H6533 red ： w/ light guide blk ： w/o light guide 2012/08/23 11 Polished Acrylic light guide (  22mm   20mm, L=20mm) To reduce photon loss G = 3.0 w/ 12kV & light guide x 5 improvement w/o  w light guide

12. H6533 ADC for single photon irradiation 12 2012/08/23 Measured by Hamamatsu Photonics w/o multiplier w/ multiplier @ 8kV

13. Possible contributions Decay time of scintillation (  ~ 250ps) TTS in multiplier (  1) TTS in H6533 (  2 ~ 120ps) Time Resolution  ~170ps τ ~900ps FWHM~1ns Gap [mm]  [ps] Gap dependence of   =900ps > 250ps Due to photon bouncing in the gap ? 2012/08/23 13

14. Position dependence of photo-gain 2012/08/23 14 HV= 10.0 kV, gap = 10mm, no light guide Donut like structure due to photons reflected back and converted to electrons ? Photo-gain position

15. Summary We are testing a large photo sensor with a fast phospher anode.  Pros: Potential merits in yields and cost because of the simple structure. Good time resolution <1ns w/ J9758 phospher  Cons: slight deterioration of efficiency and resolution due to two-stage conversions. Test production of 8-in. tubes have been made (@ Hamamatsu)  Photo-gain ~ 3  Time resolution ~ 1ns  Accumulation of know-how for production Plan  Readout by MPPC (the goal of demonstration)  Optimization of phospher material. (ex. more light yield in trade of time resolution) 15 2012/08/23 Promising !

16. Backup 16 2012/08/23

17. Recent development of inorganic scintillators 2012/08/23 17 A.Yoshikawa (IMRAM, Tohoku Univ.)

18. Samples w/ PIC (Proximity type Image Converter) 23[mm] シンチレー ター 組成最大波長 [nm] 発光量 Y[photon/MeV] 蛍光寿命 τ[ns] P47Y 2 SiO 5 :Ce420950030-50 YAPYAlO 3 :Ce3901520025-30 J9758 Confidential 40011000.5 ZnMgOZn 0.9 Mg 0.1 O36072002-3 Sample charcteristics 4.5cm ※今後の各種測定では光検出部に 1 インチ PMT を用いる 2012/08/23 18

19. Test of J9758 w/ PIC 1”PMT (H6533) directly attched to PIC output window. Bialkali PC, TTS = 270ps (FWHM) The maximum PIC HV = 12kV. Pulse laser w/ 408nm head. 19 2012/08/23 4.5cm PIC = Proximity Image Converter ADC distribution TDC distribution ~0.5ns (FWHM) w/o PIC w/ PIC @ 12kV Gain (photon-photon) as a function of PIC HV. Limit due to phosphor thickness Sub-nsec resolution possible Tsunada (Nagoya) @ JPS meeting, March 2010.