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The Fixed-Array Hodoscope of the Hall-D Tagger

The Fixed-Array Hodoscope of the Hall-D Tagger. Updates by D. Sober (CUA) GlueX Collaboration Meeting, May 2009. The Hall-D Tagging Hodoscopes. Beam energy E 0 =12 GeV coherent peak at 6-11 GeV (typically 9.0 GeV) microscope tags 800 MeV window near coherent peak

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The Fixed-Array Hodoscope of the Hall-D Tagger

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  1. The Fixed-Array Hodoscope of the Hall-D Tagger Updates by D. Sober (CUA) GlueX Collaboration Meeting, May 2009

  2. The Hall-D Tagging Hodoscopes • Beam energy E0=12 GeV • coherent peak at 6-11 GeV (typically 9.0 GeV) • microscope tags 800 MeV window near coherent peak • fixed hodoscope (tags 3.0-11.7 GeV) • located on focal plane (in front of microscope) Requirements for fixed hodoscope: • crystal alignment→ special runs at reduced rate • tagging of high-E photons (above coherent peak) → at full production rate • monitoring of photon spectrum (current integration for Eγ<9 GeV) → at full production rate • alignment of microscope • tagging of large range and near-endpoint energies (extension for experiments other than GlueX)

  3. Fixed array hodoscope: Counter 90: Eγ=9.00-9.03 GeV • 190 counters of 30 MeV bites (0.25% E0 steps) • sampling: 3.0 – 9.0 GeV (100 counters) • full coverage: 9.0 – 11.7 GeV only these 90 counters operated in tagging mode during production runs Scintillators: BC-418 (rise time 0.5 ns, decay time 1.4 ns) Counter 34: Eγ=10.68-10.71 GeV Background rates < 1% (geant simulation)

  4. Readout standard Hall-D readout electronics: LE discr., F1-TDC, fADC, Scaler (fADC for calibration and current integration of counters at Eγ<9 GeV during production runs) Original setup: PMT + VD: XP2900 (or XP3110): ~2ns rise time, ~20ns transit time, gain 8*106 (or 2*106) • New setup: • Hamamatsu R4124 (1/2” PMT): • rise time 1.1ns, transit time 12ns • 2 PMTs & bases just arrived at CUA: • performance test with fast LED pulser over next days • Modify design drawings by end of May if tests successful • resolution and rate tests during next photon run in Hall B • (spring 2010) • Estimated timing resolution: • ~8000 γproduced in 5mm scint. → ~400 p.e. → better than 200 ps μ-metal shield (annealed iron 4.5 mm thick) Cage for single PMT (easy access, adjustments ±2 mm)

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