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X*-HPD Optical Module R&D (*Crystal-scintillator viewed by small PM) I. Al Samarai, J. Busto, D. Dornic, G. Hallewell Centre de Physique des Particules de Marseille. Photonis. CERN. Baikal. From… Pr e sentation by B. Combettes (Photonis) NNN07, Hamamatsu, Japan, October 2007.

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  1. X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008 X*-HPD Optical Module R&D (*Crystal-scintillator viewed by small PM)I. Al Samarai, J. Busto, D. Dornic, G. HallewellCentre de Physique des Particules de Marseille Photonis CERN Baikal

  2. From… Presentation by B. Combettes (Photonis) NNN07, Hamamatsu, Japan, October 2007

  3. Presentation • What is the X-HPD? • History of the X-HPD; • X-HPD advantages – why develop it? • Who are the actors? • Present status inc R&D at CPPM; • Future developments X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  4. What is the X-HPD? First of all, what it ISN’T… X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  5. It isn’t like the LHC-b HPD (DEP Photonis)shown here… 80mm The X-HPD : • is big, like a hemispherical PM; • has standard bi-alkali p.c. and borosilicate window; • has no electronics in the vacuum volume; • is compatible with internal photocathode processing like PM; • is insensitive to the Earth’s magnetic field; (photoelectrons accelerated in ~25kV) 120mm Under vacuum, the X-HPD contains (only…) : • glass, • chemical products + evaporators for the photocathode, • scintilating crystal, encapsulated in aluminium, • electrodes, pins and wires, • getters, as necessary. X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  6. What is the X-HPD? • A “simple” detector of single photons with a bialkali p.c. • High accelerating field (~25kV) between p.c. & scintillating crystal (short Tdecay) under thin metallic layer (Al, 100nm) • Preferably a completely spherical geometry, with scintillator at the centre Efficiencies for electrostatic collect.+ conv.p.c. improved  Global Efficaciency ~33% (compare to ~16% PM hemi) X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  7. The first crystal-HPD: Philips SMART :Phosphor P47 (YSO:Ce)~30 manufactured (1980s-1992) History of the X-HPD G. van Aller et al. A "smart" 35cm Diameter Photomultiplier. Helvetia Physica Acta, 59, 1119 , (1986). X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  8. Baikal Quasar-370 (1983) • Hybrid (X-HPD) • -Hemisphericaldome=370 mm • -Photocathode K2CsSb • -Preamplification25 kV • Scintillator • Y2SiO5 (TTS= 2ns FWHM) • Traditional PMT • K2CsSb 13-stages =25 mm gprimary ~ 35, st ~ 2.5 ns / Npe 1 photoelectron on main photocathode  20…30 photoelectrons on small PM

  9. 200 tubes in operation since 1996 BAIKAL Quasars in operation since 1993: 200 since 1998 R. Bagduev et al., Nucl. Instr. Meth. A 420 (1999) 138

  10. The Actors: (Last meeting at RICH2007, Trieste, Oct 07) • Photonis (B. Combettes, F. Fouche, A-G. Dehaine • INFN Genova (Mauro Taiuti, D. Bersani) • CERN(Christian Joram, Jacques Seguinot; collaboration between CERN - Photonis) • CPPM(Imen Al Samarai, Greg Hallewell, Jose Busto; collaboration via GIS IN2P3-Photonis) • INR Moscow (Bayarto Lubsandorshiev {ex Baikal Quasar 370} very interested to continue development of the SMART/Quasar concept) X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  11. SMART & Quasar were the first X-HPD tubes • But scintillator in the form of disk didn’t fully exploit the potential… • Preferable to use a 3-D or ‘volume’ scintillator at the exact geometric • centre of a spherical envelope (iso-chronicity + global efficaciency • {(# photoelectrons seen)/ (# photons arriving)} ) PMT XP2982 X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  12. CERN - Photonis: Toward Development of a large spherical X-HPDhybrid photodetector • Braem +, C. Joram+, J. Séguinot +, L. Pierre *, P. Lavoute * • + CERN, Geneva (CH) * Photonis SAS, Brive (F) X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  13. T ~ 0.4 QE QE Advantages of a spherical tube with anode at geometric centre • Radial electric field • s TTS negligeable • Efficiency of electrostatic collection ~100% over ~ 3p Sr • Mu-metal screen unnecessary • Large detection solide angle (dW ~ 3p) • Gain in effective QE sensitivity by ‘Double- passage’ effect through photocathode To be compared with : ~ 70% over only 4p/3 Sr in a hemispherical PM! Nesessary for a hemispheric PM X2 compared to a hemispheric PM X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  14. 8’’ Prototype with anode in form of a metal cube (1 cm3) ‘Proto 0’ measured at Photonis Fabrication CERN . A. Braem et al., NIM A 570 (2007) 467-474 X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  15. Optical module in pressure sphere for KM3NeT? 380 mm • ± 120° acceptance • Sensitive to single photons • Time resolution 1-2 ns FWHM • Q.E. optimised 300 < l < 600 nm • dark counts <0.1 per 100 ns Pressure Sphere 17”(432 / 404) 15 Scintillating Crystal 432 mm (17”) Si sensor joint Light Guide Glass Support ceramic support Optical gel (matching ind. ref. + isolation) Small PM HV PA Inox base plate electrical feed-throughs valve X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  16. The advantages of X–HPDs in spherical geometry: Why develop them? Significant uncertainties in the rate of n production at E > ~1016eV ;n telescopes at ~ km3 scale{like ICE CUBE & KM3NeT} big enough? X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  17. Neutrino flux predictions Kappes et al., ApJ 656:870, 2007 (astroph/0607286) mean atm. flux (Volkova, 1980, Sov.J. Nucl.Phys., 31(6), 784 Estimated neutrino flux – in reach for KM3NeT All calculations show that we need multi-km3 detectors X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  18. Neutrino effective area estimation Damien Dornic, CPPM HPDs with 40% overall detection (instead of 23% for standard PMs) efficiency flat over 3p 3 X-HPDs in place of 3 standard PMs (orientation - 45°) 2 X-HPDs horizontal “Peanut” geometry (opposing direction), each storey rotated 90°w.r.t. previous) Base configuration: hexagon of 127 lines (~0.35 km3)  separated by 85m. Each line 34 storeys spaced at 15m ANTARES site parameters X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  19. Angular resolution comparison HPDs with 40% overall detection (instead of 23% for standard PMs) efficiency flat over 3p 3 X-HPDs in place of 3 standard PMs (orientation - 45°) 2 X-HPDs horizontal “Peanut” geometry (opposing direction), each storey rotated 90°w.r.t. previous) X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  20. Effective Surface Ratio:X-HPDs compared to 3 x 10” PMTs/storey X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  21. Evaluating the advantages of Spherical format X-HPDs: Volume /cost sensitivity comparison with 10” Hamamatsu R7081-20 used in ANTARES Assumptions • ~350 Cherenkov photons per cm (300-600nm) • Attenuation length 35m (combined absorption, scattering) • Photon flight 40m/sinqC (qC = 43°) =56m • Cost per ANTARES OM = PM: 995€, electronics: 600€, mechanics: 660€, sphere+other 600€ • Cost per X-HPD OM 1.5* cost of ANTARES tube of same diameter +electronics 600€ + sphere etc. 600€ + mechanics 660€ therafter scaled as ratio of areas for different diameters X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  22. ANTARES PM Assumptions: - Attenuationlength in sea water: 35m - Trajectory of muon ~ 40m fromPMs (average) ~ 350 Cherenkov photons produced per cm (300<l<600nm)

  23. X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  24. ANTARES PM Assumptions: Price of Hamamatsu 7081-20 : 995€ Sphere etc. +mechanics + electronics = 2000 € / optical module Price of 20 cm Ø p.c. X-HPD = 1.5* PM Hamamatsu 7081-20

  25. ANTARES PM Assumptions: Price of Hamamatsu 7081-20 : 995€ Sphere etc. +mechanics + electronics = 2000 € / optical module Price of 20 cm Ø p.c. X-HPD = 1.5* PM Hamamatsu 7081-20

  26. ANTARES PM Practical diameter limit to fit in 17’’ pressure sphere Assumptions: Price of Hamamatsu 7081-20 : 995€ Sphere etc. +mechanics + electronics = 2000 € / optical module Price of 20 cm Ø p.c. X-HPD = 1.5* PM Hamamatsu 7081-20 thereafter price follows (ratio of p.c. surface area)

  27. Photonishas built 2 prototypes of a new SMART (8”) and willsupply a 3rd by summer 2008 - Internaldeposition of the photocathode - Metaldisk - measure of photocurrent X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  28. SIMION 8 simulations by Imen Al Samarai (CPPM) 4/08: Testing the most simple spherical X-HPD geometry R (photocathode) 95.5mm Photocathode @ 0V R(anode) 15.6mm Anode @ 25 kV No other conductive surfaces modelled TTD (North Pole–edge PC) = 0.00022ms X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  29. SIMION 8 simulations (CPPM) 4/08: Testing S8 on the Joram–C2GT X-HPD Geometry R (photocathode) 100 mm Photocathode @ -25kV Guard ring @ -26kV R(anode) 11.7mm Anode @ 0kV Grounded metal flange TTD (Equator–edge PC) = 0.0003ms X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  30. SIMION 8 simulations (CPPM) 4/08: Centred hemispheric anode on degraded glass support R (photocathode) 100 mm Photocathode @ 0 kV R(anode) 10 mm Anode @ 25kV 20 mm diam. 60mm high glass support With degrader to 0V on outside (simulated conductive paint used in latest Joram prototype) No other conductive surfaces modelled TTD North Pole – Equator 0.0003ms

  31. SIMION 8 simulations by Christian Joram April 2008 X-HPD OM R&D KM3NeT OM meeting Genova, April 9-11, 2008

  32. Near future developments • Photonis have identified the technique for p.c. deposition as critical to cost – progress in ‘internal deposition’ • CERN-Photonis will test the 8” pure spherical geometry X-HPD with LYSO crystal (for NDIP2008, June 2008) • Parallel crystal studies (CERN-Photonis, IPN Orsay) • At CPPM, measurements of TT, sTT, HT behaviour, l-integrated photocurrent, multi-g res… (Photonis funding of stage + these PhD) Mid 2008: Fabrication & test of prototype 8” tubes with metal anode End 2008: Fabrication & test of 8” HPD tubes with crystal anodes in different configurations End 2009: Fabrication and test of prototype 15” X-HPD with best crystal anode

  33. Some Longer term developments • Progress from 8’’ prototypes to larger, up to original 15’’ of Flyckt/Val Aller SMART? (Photocathode deposition  internal or quasi-internal processing: Cost/unit driven lower than hemispherical PM of same Ø?) • In parallel, tests of an 8” prototype in a sphere at ANTARES/NEMO/NESTOR (need to pass to ‘weaponisation’ phase: compatibility with power & r/o system) • Development from Baikal 24V25kV DC-DC supply: Low power Cockroft-Walton multiplier: reliability issues, Can we build from designs of TV tube HV supplies (compatibility of reqt?) (huge statistical MTBF sample + Photonis-Philips connection) • These above issues to be addressed in WP3/ANR context  We welcome new collaborators, ideas to this effort !

  34. Conclusion • Pure spherical geometry X-HPDs based on Flyckt/Van Aller Philips SMART tube could be very promising Čg – detectors for underwater n telescopes • ~100% photoelectron collection eff. (over 3p Sr) (& sTT<1ns ) • (c.f. 65% over ~ 4p/3cathode surface area in ‘hemispherical’ PM) • Much larger photocathode area than same Øhemispherical PM + suppression of m-metal cage • Improved Q.E. (transmissive  reflective) over large % of 3p  enhanced overall detection effiency • Improved multi-g sensitivity with small PM readout, possible directionality for segmented PC + multi-anode PM  Cost savings: larger water volume instrumented with a given number of photon detectors

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