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

DiscriminatorCFD

JLAB TDC

Sampling ADC

Timing resolution:t < 200 ps

Hamamatsu H-8500 SpecsOur 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)

Anode Uniformity (our tube)• Measurement provided by Hamamatsu• The only measurement station for reproduction and detailed scan presently at SLAC

Also variation within pixele.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 x40Based on Elantec 2075CS OP-amp

16 channels withconnector to MAPMT outputs

For pulse-shape uniformity (CFD)need probably somewhat higher gain.

The EL2075 series is discontinuedand 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 outputGain about 1150% 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 testsRestoration of cleanroom (new filters sponsored by UT)

Addition of ultra-clean section withSeparate entrance area.

Light-tight boxfiber optics

DIRC quartz bar packed

Summary

The H8500 is a good representation of the final choice ofphoto-detector

The SLAC 1-stage amplifier is a good starting pointbut needs to be replaced

For studies of the readout scheme with respect tosingle photon timing we urgently need a

- Laser diode system wavelength ~ 408 nm, time resolution < 50ps Jerry uses PiLas from APS controller + head ~ $14k