Fall 2019 DIRC Commissioning

Expected Conditions

• Beam energy expected 11.6 GeV
• Solenoid on at 1350A (except for straight track runs)
• CW Beam current:
  • Range: 50 nA - 600 nA. 250 MHz frequency.
• Expect to take commissioning datasets at:
  • Low-intensity: 100 nA on 50 um diamond
  • Moderate-intensity: 200 nA on 50 um diamond
  • High-intensity (GlueX-II): 300 nA on 50 um diamond
• FFB on or Position Slow Lock on (FFB doesn't operate below 50nA).
• Radiators:
  • Goniometer radiators:
    • Several 50 μm diamonds (4·10^-4 R.L., 7×7 mm²)
    • 40 μm Al radiator (44.9·10^-5 R.L.)
  • Amorphous
    • 1.64 µm Al (1.86·10^-5 R.L)
    • 10 µm Al (11.2·10^-5 R.L.)
    • 30 µm Al (33.7·10^-5 R.L.)
• Tagger quadrupole on (-4.2 A).
• Collimator hole: 5 mm diameter
• Targets: LH2 cryogenic target

Commissioning Goals

• Integrate North and South Optical box readout with general Hall D DAQ and online/offline monitoring at GlueX-II intensities
• Implement reconstruction algorithms and compare data/MC: # detected photons, Cherenkov angle resolution
• Calibrate per-pixel timing offset of MAPMTs using LED system
• Determine tracking position and angle resolution at DIRC using GEM/TRD detectors
• Determine geometric alignment parameters (position and angle offsets) for optical components

Commissioning Observables

• "Ring" images for tracks with fixed kinematics (binned in position space over bars) overlaid on MC distributions
• Per-pixel timing and Cherenkov angle differences (measured - LUT expected) to confirm geometry
• Number of detected photons/track
• Single photon resolution (SPR) per pixel

Commissioning Timeline, Tasks and Milestones

• January 2-10: Integration of DIRC crate with DAQ and initial test of readout with standalone MAPMT module (Ben, Sergey, Sasha)

• January 30 - February 12 (commissioning with beam):
  • Implement LED trigger into DAQ --- Ben, Sasha
    • Detemine optimal LED conditions (amplitude and trigger rate) to be added to production trigger --- TBD
  • HV and threshold scans with LED data (2 weeks after install) --- TBD
    • Duplicate scans of HV and thresholds as used in laser test setup (see below)
    • Determine initial HV and threshold settings for LED and beam data
  • Initial time offset calibrations with LED data (3 weeks after install) --- Yunjie

• November 25 - December 20 (commissioning with beam):
  • Complete integration with DAQ under low-intensity beam conditions: (1 week)
    • Evaluate scaler rates and distributions relative to MC predictions
    • Determine what global parameters can be optimized (beam current, bar box position, etc.) can be optimized
  • Production data taking with all sub-detectors in nominal condition (1 week, standard production)
    • FCAL-BCAL production physics trigger with interleaved DIRC LED and random triggers
    • Collect sufficient statistics for optical alignment with identified ρ and φ, as well as more exclusive reactions with tagged K_s

• • Intensity scans (2 days)
    • Evaluate rate dependence and backgrounds for both high and low luminosity

Calibration datasets

Straight-track data (3 shifts)

• For alignment of the GEM/TRD we need to acquire production samples with the magnetic field off
  • Question: Can the initial detector/trigger checkout be done with the magnetic field off?
• Need a straight-track sample at each of the 3 TRD positions with the full GEM readout for tracking and alignment studies
  • Question: How much time is needed for to acquire these statistics? One shift?

Full GEM readout (3 shifts)

• The electronics for the full GEM readout are limited to ~5kHz,
• At least one large dataset at each of the 3 TRD positions will be required with the full readout for tracking and alignment studies
  • Question: One shift at each position with Low-intensity conditions?

Raw mode readout

• No requirement for DIRC but other detectors may need raw mode readout periodically.
• Question: What datasets does the TRD group need with raw mode readout for cluster counting studies?

Production datasets

• Expect to collect at least ~1 billion events for each configuration (10 in total) to reasonably compare photon yield and hit time resolutions. We expect these datasets should all be usable for the total statistics needed in single photon Cherenkov angle resolution and detector alignment studies.
• At each intensity collect dataset for 3 different DIRC threshold settings.
• The TRD/GEM readout by the f125 should be included in the production running, which should operate at all the intensities described below.
  • Other GEM detectors readout by APV are rate limited to ~5kHz and will be included only in calibration datasets described above.
  • Need production datasets at each of the 3 TRD/GEM positions, but only for one intensity/threshold setting.

Low-intensity Set

• Beam current = 100 nA with 50 um diamond
• DAC thresholds set to pedestal + [50, 100, 200], with all HV=1000 V.

Moderate-intensity Set

• Beam current = 200 nA with 50 um diamond
• DAC thresholds set to pedestal + [50, 100, 200], with all HV=1000 V.

High-intensity tests

• Goal: Increase photon beam as close to high-intensity conditions (5e7 g/s in the coherent peak).
• Beam current = 300 nA with 50 um diamond
• DAC thresholds set to pedestal + [50, 100, 200], with all HV=1000 V.
• Additional Requirements:
  • Lower drift chamber HV (Beni/Lubomir)
  • Turn off HV for TAGH counters below microscope? (Sasha)
  • Tune trigger/DAQ settings (Sasha/Sergey)

Daily Tasks during commissioning

The tasks described here require no beam in the Hall (collimator in blocking position). These should be completed each day to monitor PMT performance over the course of commissioning and should be done during scheduled beam downtimes if possible:

1. Threshold scan (15 minutes): Special DAQ configuration run at pre-start to scan DAC thresholds and record scaler rates to monitor pedestals for all channels
   • See instructions on Operations Wiki
2. Dark rate run (15 minutes): Production DAQ configuration including LED trigger at 5 kHz and LED bias = 0 V, collect 5M events.
3. LED run (15 minutes): Production DAQ configuration including LED trigger at 5 kHz and LED bias = 12.4 V, collect 5M events.

DIRC LED skims

/cache/halld/RunPeriod-2019-01/calib/ver01/DIRC-LED/

Additional studies

Magnetic Field Study During Solenoid Magnet Ramping

• To monitor the DIRC occupancy variation under magnetic fields, we will run the LED pulser runs throughout the magnet ramp. Runs should be taken with the LED bias = 12.4 V with the pulser running at 5 kHz. All HV=1000V, MAROC gains equalized (version 1) and DAC thresholds set at pedestal + 100.