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Study of scintillator/PMT properties for PoGO experiment

Study of scintillator/PMT properties for PoGO experiment. August 25, 2003@ PoGO Teleconference Tsunefumi Mizuno mizuno@SLAC.Stanford.EDU. BGO Transmission efficiency: pp.2-3 Comparison between two PMTs (normal cathode vs. prism one): pp.4-8 Summary: p.9. BGO transmission efficiency (1).

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Study of scintillator/PMT properties for PoGO experiment

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  1. Study of scintillator/PMT properties for PoGO experiment August 25, 2003@ PoGO Teleconference Tsunefumi Mizuno mizuno@SLAC.Stanford.EDU • BGO Transmission efficiency: pp.2-3 • Comparison between two PMTs (normal cathode vs. prism one): pp.4-8 • Summary: p.9

  2. BGO transmission efficiency (1) 241Am(59.5keV) Hexagonal plastic scintillator BC404 (fast scintillator) wrapped with VM2000. 20cm long Lead block • two types of BGO scintillators wrapped with teflon tape. • manufacture way of polishing; rough surface in sides. Top/bottom surfaces are polished. • Tune’s proposed way polishing; rough surface in bottom. Other planes are polished. Princeton PMT(H3178) We compared transmission efficiency between two types of BGO scintillators; one is in the original way of polishing and the other is re-polished in the way proposed by Tune.

  3. BGO transmission efficiency (2) Peak~3.15 Through re-polished BGO Peak~2.36 Spectrum obtained without BGO fitted with gaussian+BG function. Through BGO in original way of polishing. Peak~2.30 Transmission efficiency: ~75%(re-polished BGO) ~73%(original way of polishing)

  4. Comparison between normal cathode and prism one (1) 55Fe(5.9keV) Hexagonal plastic scintillator BC404 (fast scintillator) wrapped with VM2000. 20cm long Re-polished BGO wrapped with teflon tape Two types of PMTs borrowed from TIT; a) R7899-mod1(normal cathode; S/N AA2190) b) R7899-mod2(prism cathode; S/N ZL1692) We compared the scintillator light yield between normal cathode PMT and prism cathode one in the condition close to PoGO mission(pp.5-6). We also investigated the HV dependence of the light yield(pp.7-8).

  5. Comparison between normal cathode and prism one (2) R7899-mod1 (normal cathode), -1000V Single photo-electron events 55Fe background ??? Background is unstable? BG subtracted spectrum fitted with poisson function. Npe~3.1. Spikes in spectrum are due to the mismatch between histogram binning and ADC resolution. Funny structure seen in ~3.5V needs to be investigated. Normalized BG and 55Fe spectra. (Live time is taken into account)

  6. Comparison between normal cathode and prism one (3) R7899-mod2 (prism cathode), -1000V Single photo-electron events 55Fe background ??? BG subtracted spectrum fitted with poisson function. Npe~3.5. Spikes in spectrum is due to the mismatch between histogram binning and ADC resolution. Funny structure seen in ~3.5V need to be investigated. Normalized BG and 55Fe spectra.

  7. Comparison between normal cathode and prism one (4) R7899-mod2 (prism cathode), -1500V Single photo-electron events 55Fe background ??? Background is unstable? BG subtracted spectrum fitted with poisson function. Npe~3.6. Spikes in spectrum is due to the mismatch between histogram binning and ADC resolution. Funny structure seen in ~3.5V need to be investigated. Normalized BG and 55Fe spectra

  8. Comparison between normal cathode and prism one (5) R7899-mod2 (prism cathode), -800V Single photo-electron events Background 55Fe Background is unstable? BG subtracted spectrum fitted with poisson function. Npe~3.45. Spikes in spectrum is due to the mismatch between histogram binning and ADC resolution. Normalized BG and 55Fe spectra

  9. Summary • BGO transmission efficiency is ~75%. Although it does not depend on the way of polishing very much, Tune’s proposed way of polishing showed slightly better efficiency. • Prism cathode PMT gives a little bit higher light yield (by ~10%) than normal cathode one. • Absolute light yield is >=0.5 p.e./keV for 20cm fast scintillator (wrapped with VM2000) with BGO (wrapped with teflon tape). This does not depend on the applied voltage very much.

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