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Advances in Photosensors for DBD and DM Experiments: Exploring LAAPD Developments

This research outlines advancements in photosensors, specifically focusing on Large Area Avalanche Photodiodes (LAAPDs) for Double Beta Decay (DBD) and Dark Matter (DM) experiments. The study highlights the impressive quantum efficiency of LAAPDs, operational capabilities at low temperatures, and comparative resolution enhancements over conventional PMTs. New developments in PMTs from Hamamatsu, which promise improved sensitivity, are also discussed. Future work includes investigating potential failures of LAAPDs and testing new devices, aiming to optimize detection in cutting-edge experiments.

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Advances in Photosensors for DBD and DM Experiments: Exploring LAAPD Developments

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  1.  Photosensors for DBD & DM experiments Woonku Kang, Jungil Lee, Seunghyun Moon, Kyungju Ma, Yeongduk Kim Sejong University for KIMS collaboration Korea-China Joint workshop 2007. 11. 26

  2. LAAPD(Large Area Avalanche Photodiode) Advanced Photonics사의 16mm 직경의 LAAPD (world largest)

  3. 5mm LAAPD Solovov(1999) • High quantum efficiency : 약 90% @ 500nm LAAPD는 -200도에서도 작동. Significantly reduced dark current Higher gains can be achieved Noise level can be reduced CaMoO4 + LAAPD can be excellent detector for DBD

  4. Previous Results of LAAPD Room temperature measurements • CsI(Tl) + 16mm LAAPD • 4.8%FWHM for 662 keV • LAAPD has better resolution than PMT due to high Q.E. 5.9 keV X-ray 9.3% FWHM =4.0% RMS M. Moszynski

  5. ORTEC PREAMPLIFIER 142AH (High Voltage 용 ) Crystal POWER SUPPLY(HV) Source LAAPD Output (Low Temperature) Output (Room Temperature) ORTEC AMPLIFIER 571 Test Setup - CsI(Tl) & CamoO4(Russia) ~10x10x10mm

  6. # of events (6%FWHM) Back scatters Comptonedge Channel number CsI(Tl)+LAAPD @Room temperature We confirmed good resolution of CsII(Tl)+LAAPD detector at room temperature

  7. mV p2 p0 p4 p5 Micro sec p6 CaMoO4+LAAPD @LowTemp • Decay time ~ 100 ms @ -150 oC • But shaping time of AMP is limited by 10 ms • Analyzed PreAmplifier Signal directly. • Source ; Cs-137 • Temp ; -159.2 oC ± 0.1

  8. CaMoO4+LAAPD @-159oC In reality, the resolution will be worse due to poorer light collection and large size of crystal.

  9. Future plan • Try to understand the cause of LAAPD failure, specially for the dye sensor. • New cryostat and vacuum chamber for LAAPD and new PMT + CaMoO4 tests down to 70K temperature.

  10. New PMTs of Hamamatsu - first talk with company -

  11. Current KIMS PMT • Green extended ETL pmt(9269B) • 26% @ 400nm • 17% @ 500nm 3” PMT (9269QA) : Quartz window, RbCs photo cathode ~5 Photo-electron/keV with CsI(Tl) crystal.

  12. new Hamamatsu PMTS • Ultra Bialkali : • R7600 or 3” Glass Bulb

  13. Hamamatsu will develop a new PMT based on R8520AL(XENON Group) with Ultra bialkili cathode for KIMS. • Size : 1” • Working temperature -100oC • Metal Case with Quartz window. • Will try to deliver a sample to KIMS until end of this year We will test a CaMoO4 crystal coupled with PMT at low temperature.

  14. Development of new hexagonal PMT (HAMAMATSU R8778MOD) for XMASS 800 kg • High quantum efficiency ~ 40% @ 175 nm • Metal package with Quartz window • Low temperature, will be immersed in Lxe.

  15. Test chamber Hexagonal PTFE Top PMT Inside of the chamber Bottom PMT

  16. LED (2mm thick PTFE filter) Hexagonal PTFE and Co-57 source position Distance between two PMTs : 1.5cm

  17. result 122keV 57Co data 18.9 p.e/keV 136keV Some photons are blocked by the source itself Photoelectron statistics limit of the resolution = 2.1%

  18. # of photoelectrons in various LXe experiments

  19. XENON group (at TAUP 2007) New Measurement of Scintillation Efficiency for < 10 keVr XeCube • Hamamatsu R8520 1’’×3.5 cm (metal channel) • bialkali-PC, Quartz window,operates at -100ºC and 5 bar • Quantum efficiency > 20% @ 178 nm • Custom HV divider on Cirlex base σ/E = 7.8 % http://xenon.astro.columbia.edu/

  20. Calorimetric 136Xe DBD • Q=2467 keV • 208Tl 2614.5 keV Compton edge 2381.7 keV • 0.7% energy resolution(17keV) @ 2467keV expected.  DBD peak and Compton edge separation is ~5 sigma. • Maybe worth to study in detail, specially for events between full peak and Compton edge for a specific detector geometry and shielding. • Both single & double phase can be tried.

  21. Summary • LAAPD has (dis)advantage. • New PMTs will improve the sensitivities of DBD and DM experiments. • Constant optimization is important.

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