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Published byEdmund Morris Modified over 9 years ago
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A DIRC for GlueX April 7, 2006 S. Berridge, S. Spanier
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Readout Scheme Our present choice for the photo-detector is the H-8500 tube from Hamamatsu. The final choice will be this one or a similar tube. The pixelation allows for different readout configurations by shortening several output channels together. We closely follow the R&D at SLAC focusing on potential differences (relaxation of specs with respect to a B-factory DIRC) The main difference we will test is the (SLAC) constant-fraction discriminator versus single/double leading edge (new) 8x8 channels H 8500 Amplifier > x40 Discriminator CFD JLAB TDC Sampling ADC Timing resolution: t < 200 ps
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Hamamatsu H-8500 Specs Our tube: 8x8 anodes 6mm x 6mm / pixel QE >~ 20% gain ~ 2.5 10 6 rise time: 800 ps cross talk: ~ 3% compare nominal specs to current manufacturing, improving somewhat (nominal)
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Anode Uniformity (our tube) Measurement provided by Hamamatsu The only measurement station for reproduction and detailed scan presently at SLAC Also variation within pixel e.g. boundary/corner effects Measurement : define tolerance Calibration Map of the relative QE pixel by pixel
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Jerry Va’vra’s preamp (loan) This is Jerry’s first version with gain x40 Based on Elantec 2075CS OP-amp 16 channels with connector to MAPMT outputs For pulse-shape uniformity (CFD) need probably somewhat higher gain. The EL2075 series is discontinued and world supply has run out. Present R&D: Single stage amplifier with a replacement (higher bandwidth) OP-amp. (SLAC has a 2-stage Version)
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Pulse measurement MAPMT dark pulse preamp output Gain about 11 50% increase in risetime.
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Raw pulse variation 5 sec of MAPMT dark pulses Preamp output
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Preparation of the DIRC LAB at UT: Tube characteristics VME 64x
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Preparation of the DIRC LAB at UT: Radiator tests Restoration of cleanroom (new filters sponsored by UT) Addition of ultra-clean section with Separate entrance area. Light-tight box fiber optics DIRC quartz bar packed
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Summary The H8500 is a good representation of the final choice of photo-detector The SLAC 1-stage amplifier is a good starting point but needs to be replaced For studies of the readout scheme with respect to single photon timing we urgently need a - Laser diode system wavelength ~ 408 nm, time resolution < 50ps Jerry uses PiLas from APS controller + head ~ $14k
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