1

The Fixed-Array The Fixed-Array Hodoscope Hodoscope

of the of the Hall-D TaggerHall-D Tagger

Updates by D. Sober (CUA)

GlueX Collaboration Meeting, May 2009

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The Hall-D Tagging The Hall-D Tagging HodoscopesHodoscopes

• 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)

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Fixed array hodoscope:Fixed array hodoscope:

Eγ (GeV) counter widthsample fraction

(at 60MeV spacing)

tag rate (MHz/MeV) (at 100MHz on target)

counting rate(at 100MHz on target)

3.0 – 5.0 4 - 5 mm 50% 0.39 - 0.58 MHz/MeV ~11 - 17 MHz

5.0 – 7.0 5 - 6 mm 50% 0.34 – 0.39 MHz/MeV ~9 - 11 MHz

7.0 - 9.0 6 - 8 mm 50% 0.34 – 0.45 MHz/MeV ~ 9 - 14 MHz

9.0 – 11.7(above coh. peak) 8 – 47 mm

100%2 counters/60 MeV 0.12 - 0.18 MHz/MeV 3.5 - 5.5 MHz

• 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 90: Eγ=9.00-9.03 GeV

Counter 34: Eγ=10.68-10.71 GeV

Background rates < 1% (geant simulation)Background rates < 1% (geant simulation)

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ReadoutReadout

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)

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 γ produced in 5mm scint. → ~400 p.e. → better than 200 ps

Cage for single PMT (easy access,

adjustments ±2 mm)

PMT + VD:XP2900 (or XP3110):~2ns rise time, ~20ns transit time,gain 8*106 (or 2*106)

μ-metal shield(annealed iron4.5 mm thick)

Original setup: