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Four days scheduled for commissioning program
- 1 Establishing Beam for the first time
- 2 BB and SBS Commissioning
- 3 Initial checklist
Establishing Beam for the first time
Beam centering and raster calibration [8 hours]
This program is run by Simona M. Basic outline is below
- BB, SBS, and corrector magnets are OFF. Target in empty position.
- Accelerator will establish beam straight to the dump and use this straight trajectory to find BPM offsets. Accelerator will ramp up the SBS and corrector magnets.
- Harp scans now done to measure beam intrinsic spot size >320um in x and y ( ).
- Call Sean to let him know you are ready for GEMs so that foil z positions can be resolved.
- BB is now ramped up (see the procedure) and Preshower, Shower (collectively BB CAL), and Hodoscope HV is ON.
- Carbon target foil with 1mm hole inserted and imaged. Position of beam verified and raster size calibrated.
- Ion chambers now calibrated with foils
- BPMs and BCMs calibrated.
BB and SBS Commissioning
At this point we have good beam and characterized beam monitors and are ready to commission our experiment.
- This segment begins using Carbon foils and BB On (700A) with SBS OFF. Raster will be on.
- Call system experts: BigBite (Provakar), HCal (Jiwan), GEMs (Andrew, Holly, Zeke)
There are two parts to this plan:
- Commissioning detectors, optimizing DAQ+replay, setting thresholds and HV, timing the coincidence trigger
- Taking optics data. This will require transitioning to the glass cells.
Detector Commissioning Program
What is the thickness of the foils in the solid targets? Can't do rate estimate without those numbers.
- Turn on All Major Detectors
- Trigger rate scaler check. Take a run at 10,20,30 uA. What configuration in CODA? What prescales? We expect 3-10 Hz/uA (on carbon?). Is this what we see?
- SBS timing and amplitude check. Jiwan will do this.
- Turn SBS on and go through procedure to establish corrector currents.
- Perform GEM High Voltage and Commissioning Plan. The full commissioning procedure can be found here. People: Andrew, Holly, Ezekiel, Sean, Anu, John
- GRINCH commissioning call Carlos
Electron Arm (BB)
Andrew Puckett and Holly Szumila-Vance are the contact people for BigBite optics calibrations
The commissioning plan (not necessarily in the following order):
- Low current, zero-field runs: Purpose: align GEMs relative to BigBite Magnet and target center using straight-through tracks from with sieve slit and single-foil "point" target. Initial alignment comes from survey. Internal GEM relative alignment for tracking purposes is done separately using Andrew's script. The GEM HV scan/efficiency plateau should either already be done or can be done concurrently as part of this program.
- BigBite and SBS Magnets are OFF.
- Target = single-foil carbon.
- Beam current = 1 uA or as low as we can go such that the BCMs still work. Note that GEMs can tolerate much higher charged particle flux than wire chambers and should tolerate magnet off conditions better than MWDCs as soft photon flux is unaffected by magnetic field
- Beam is unrastered ("point" source of straight tracks for precise alignment)
- Sieve slit is IN.
- Trigger = BigBite calorimeter, threshold set for quasi-elastic from carbon, rate <~ 5 kHz
- Time required probably ~1 h or less. Need ~few-hundred straight-through tracks per sieve hole.
- Optics data with sieve slit plus optics targets (and some LH2 data with sieve slit IN): Purpose: calibrate BigBite angle and vertex reconstruction (and also momentum).
- BigBite magnet is ON, energized at full current of ~710 A with polarity set for up-bending electrons
- SBS magnet is ON, at reduced current (~30% of max at commissioning kinematics)
- Sieve slit is IN
- Prefer unrastered beam on solid-foil optics targets. Always rastered beam on cryo-targets
- Targets are:
- Optics (8 foils at z = 0, +/-7.5 cm, +/-15cm, +/-22.5cm, +30 cm)
- H2 15 cm (without radiator)
- Trigger is BigBite calorimeter
- Need ~few hours data on each optics target plus LH2 target with sieve in. Possibly with lower threshold in BB or higher beam current, depending on rate. Need to collect ~500-1,000 events per sieve hole per target foil for each optics target position. Additional LH2 elastic data with sieve slit may also help with momentum calibration.
- Starting optics model is from g4sbs simulation. Need to know actual magnet current to determine appropriate scale factor for simulation magnetic field to generate starting optics model. Approximate starting optics model helps to more easily identify which tracks come through which sieve holes from which foils. Unclear, but we might end up having to turn off SBS GEMs during BB multi-foil running depending on the good electron rate.
- H2 elastic data without sieve slit: Purpose: Calibrate BigBite momentum reconstruction and BBCAL and HCAL energy reconstruction. Also calibrate BigBite and HCAL trigger threshold from mV to energy deposit
- With BB magnet ON at full current
- Sieve slit is OUT (require controlled access and trained/authorized personnel to insert/remove sieve slit)
- Rastered beam at nominal
- Target is H2 15 cm without radiator
- beam time/data requirements for this phase are driven by calorimeter calibration needs, not optics/momentum calibrations
- Use angle-momentum correlation for elastic scattering to calibrate momentum reconstruction matrix elements, assuming angle reconstruction already calibrated. We need to know beam energy for this. Do we need a dedicated Arc and/or eP beam energy measurement?
With the BB calorimeter calibrated (which gives us the electron momentum), we now can calibrate the response of the HCAL detector to determine the proton momentum, where we use the LH2 target.
- Target: LH2
- Beam: 5 μA, raster (2x2 mm^2) (?)
- DAQ Configuration: Name, BB CAL/HCAL coincidence trigger
- Call MCC to stop the beam.
- The TO inserts the LH2 target.
- The sieve is pulled OUT (if it is in).
- The BB and SBS magnets are ramped to their nominal currents.
- Start a new run
- Call MCC to deliver beam.
- After X minutes, stop the run and check the beam setup using spot++. Work with MCC to optimize beam delivery on target.
- Start a new run for X minutes. Shifters monitor the data using the online software
- Experts perform offline/nearline analysis to produce plots to illustrate the calibration/success of the measurement.
BB GRINCH Commissioning
Software and DAQ
- Software: Andrew Puckett, Mark Jones
- Event displays
- Does 50k replay work and do we need any plots added
- DAQ: Alexandre Camsonne, Mark Jones, Bob Michaels, Ben Raydo, B. Moffit
- Control GUIs
Training and safety
- Hall A walkthrough SAF110
- Read and signed COO, RSAD, ESAD
- Target training: Arun, Gordon, Bill