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Hiroyuki Sekiya Kamioka , ICRR/IPMU, University of Tokyo

A novel imaging device based on UV scintillators and a large area gas photomulitiplier 11 th i WoRiD July 1 2009. Hiroyuki Sekiya Kamioka , ICRR/IPMU, University of Tokyo C.Ida , H .Kubo, S.Kurosawa , T.Tanimori Dep. of Physics, Kyoto University

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Hiroyuki Sekiya Kamioka , ICRR/IPMU, University of Tokyo

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  1. A novel imaging device basedon UV scintillators and alarge area gas photomulitiplier 11thiWoRiD July 12009 Hiroyuki Sekiya Kamioka, ICRR/IPMU, University of Tokyo C.Ida, H.Kubo, S.Kurosawa, T.Tanimori Dep. of Physics, Kyoto University • A.Yoshikawa, T.Yanagida, Y.Yokota • IMRAM, Tohoku University • K.Fukuda, S.Ishizu, N.Kawaguchi, T.Suyama • Tokuyama Coporation

  2. Contents • Motivation –Gas Photomultiplier • VUV scintillator • Setups of the detector • Analog property • 1p.e. level pulse mode operation • Digital property • Operation as a novel imaging detector • Summary

  3. Large Area Position resolution Low cost Small Volume Low background Possible features Gas Photomultipliers Photocathode + Micro Pattern Gaseous Detector Future Large Volume Detectors for Dark Matter/neutrino Inside of the Super-K detector

  4. CsIphotocathode for GPM • Although only sensitive to <200nm, easy to handle (⇔Bialkali PC) • Strong for ion feedback flow: Low Ion induced electron emission probability • Stable in dry air. • Many possible applications • Liq. Xe/Arscintillators (λ<180nm) • Single phase detector (DM search, XMASS) • Tube type • Double phase detector • Both charge & photon detection • VUV Crystal scintillators (our target) • Like visible scintillators + PMT • PET • Color X-ray CT • Gamma Camera

  5. UV scintillator X-ray induced luminescence spectrum • We are developing Nd3+ doped fluoride crystals which emit VUV photons through 5d-4f transition. • This time, we focused on LaF3(Nd) as a low intensity light source in order to test the detector for 1p.e. level. • λ=172nm, τ= 6ns wavelength(nm) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 150160 170 180 190 200 210 220 230 240 250 260

  6. LaF3(Nd) as a light source • 2cm size crystal covered with Teflon +3kBqα from 241Am • Light Yields were measured with VUVsensitive PMTR8778 • (HAMAMATSU) • Developed for XMASS • Quartzwindow • UV enhanced bialkali • 30 p.e. Quantum efficiency30%＠172nm →　LY 100 photons/5.5MeVα

  7. Semitransparent Photocathode 5tMgF2 window Al vapor deposition on 10mm edge. 34mmΦCsI vapor deposition “The thickness is same as that of CsI PMTs(100M)” by Hamamatsu QE curve

  8. μPIC & GEMs: electron multiplier • Many R&D efforts on CsI+MPGDs. • Cascade GEM/MHSP/THGEM and so on. ex) NIM A 595(2008) 116 and its refs • Our strategy is GEMs+μPIC • GEMs for ion feedback blocking • μPIC for high gain / position resolution μPIC GEM/SMASH Cathode strips Anode strips • Laser etched. • 100um LCP • / 50um Capton • 140um pitch • 70umΦ • RIKEN/SciEnergy • Advanced • MSGC • 400μm pitch • strips • Kyoto/DNP 400μm 400μm

  9. 30cm size Area MPGDs are already used in many applications. For the prototype detector, partly because the window size is limited for the moment, we adopted 10cm size MPGDs. Large Area μPIC & GEM 30cm μ-PIC 28cm GEM 28cm 23cm 10cm μ-PIC 10cm GEM

  10. Set up for testing analog properties • 2 100μm-GEMs+μPIC with CsI photocathode • Ar＋C2H6（90：10）1atm • Gas gain 2.6 x 105 • μPIC465V • GEMｓ422V LaF3 241Am CsI Ed= 0.3kV/cm Electrode 13mm 2mm 4mm EI= 1kV/cm

  11. Photon Signal • Readout: μPIC64 stripssummed • Amplified with CP581 preamp (1V/pC) Clearpluse co., ltd. 120mV The gas gain 2.6×105 Detected number of photoelectrons 120mV/1V×1pC/(1.602×10-19)/ 2.6×105=2.9 p.e.

  12. Spectrum Sensitive to 1p.e. ! • Source intensity 100 photon →　QE　～　1-2 % ∫ × dλ = Agrees with QE curve and the luminescence spectrum

  13. Set up for testing imaging properties • 2x50μm-GEMs+μPIC with CsI photocathode • Ar＋C2H6（90：10）1atm • 256ch x 256ch readouts • 2.6MBq 241Am for higher rate test LaF3 CsI Ed= 0.5kV/cm 2.5mm 2mm EI= 2.95kV/cm 2mm • μPIC490V • GEMｓ280V Gas gain 6.7 x 105

  14. Readout system NIMA 513(2003) 94 ASD chip for ATLAS TGC 0.8V/pC Position Encoder FPGA x 3 100MHz clock Obtained image

  15. Crystal Shape Reconstruction • 18x21x20mm3 LaF3(Nd) + 2.6MBq241Am Parallel composition Diagonal composition

  16. Image Expansion by Electric Fields • Lens Effect between the PC and the 1st GEM 241Am LaF3 • X 1.6 expansion • Large area MPGDs make the expansion possible and this effect may enhance the position resolution of Gas PMTs against the diffusion.

  17. Evaluation of the magnification LaF3 • 0.1t PVC sheetsinserted Uniformly x1.6 expanded 10mm distance Slits 2mm x 15mm Vertical composition horizontal composition Y projection X projection

  18. More Examples 5mm distance Slits 2mm x 15mm 犬 Star

  19. Summary • A new UV sensitive gas PMT with GEM/μPICis being developed. • Although the QE is still limited, 1 p.e. level signal is clearly detected. • Combined with new VUV scintillators, new radiation imaging sensors are also being developed. • With LaF3(Nd), the imaging capability of the detector was tested. It might have sub 1mm position resolution. • Electric lens effect (expansion) was demonstrated thanks to the large area MPGDs.

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