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 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

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

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

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)

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

Raw pulse variation 5 sec of MAPMT dark pulses Preamp output

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

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

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