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A DIRC for GlueX

A DIRC for GlueX. April 7, 2006 S. Berridge, S. Spanier. 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

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A DIRC for GlueX

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  1. A DIRC for GlueX April 7, 2006 S. Berridge, S. Spanier

  2. 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) Sampling ADC H 8500 JLAB TDC Timing resolution: st < 200 ps Amplifier > x40 Discriminator CFD 8x8 channels

  3. Hamamatsu H-8500 Specs • Our tube: • 8x8 anodes • 6mm x 6mm / pixel • QE >~ 20% • gain ~ 2.5 106 • rise time: 800 ps • cross talk: ~ 3% • compare nominal specs to current manufacturing, improving somewhat (nominal)

  4. Measurement provided by Hamamatsu • The only measurement station for reproduction and detailed scan • presently at SLAC Anode Uniformity (our tube) Map of the relative QE pixel by pixel • Also variation within pixel • e.g. boundary/corner effects • Measurement : define tolerance • Calibration

  5. 16 channels with connector to MAPMT outputs This is Jerry’s first version with gain x40 Based on Elantec 2075CS OP-amp Jerry Va’vra’s preamp (loan) 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)

  6. Pulse measurement MAPMT dark pulse preamp output Gain about 11 50% increase in risetime.

  7. Raw pulse variation 5 sec of MAPMT dark pulses Preamp output

  8. Preparation of the DIRC LAB at UT: Tube characteristics VME 64x

  9. Preparation of the DIRC LAB at UT: Radiator tests Addition of ultra-clean section with Separate entrance area. Restoration of cleanroom (new filters sponsored by UT) Light-tight box fiber optics DIRC quartz bar packed

  10. 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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