Beam Commissioning Plan
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Draft Outline for Commissioning
Review Sequence
- Electron beam
- OSP and small internal review in order to power and map tagger magnet
- Transfer of tagger magnet operation to accelerator, so that it can be reviewed as part of ARR II (nominally Jan)
- Photon beam
- Review of photon beamline (radiator to photon beam dump). Nominally scheduled for March, at least 3 months prior to beam delivery
- This includes review of the tagger hodoscope and microscope, profile monitor, active collimator, halo monitors, and other photon beam monitors.
- Experimental Equipment Hall D
- Experimental apparatus in Hall D (prior to use with beam)
Electron beam
Goals
- Safely deliver electron beam to the electron beam dump \cite{shielding}
Assumptions
- Accelerator has qualified the machine protection system (MPS) and the personnel safety system (PSS) for the tagger building
- Assume steel blocks (> 20" thick) are stacked in front of the photon beam pipe to the hall to prevent any direct beam spray from traveling down to Hall D.
Checklist at low current I~1uA, tune mode
- Check beam is centered on the beam dump
- Scan position of beam over the area of the radiator
- Check single rates at various positions in the tagger enclosure (electronic racks)
- Check single rates at the location of the tagger microscope
- Check single rates at the location of the tagger broad band hodoscope
- Verify tagger magnet excitation curve matches predictions, e.g. for different beam energies
- Verify controls for all beamline elements work as expected
- Check radiation levels in the tagger hall
- Esablish location in the hall for electronic racks safe from radiation
- Identify sources of background (scraping) in the hall.
- Check Fast Shutdown system
Checklist at low current I< 100 nA?, CW
- Verify proper operation of beam as in pulsed mode
- Check single rates at various positions in the tagger enclosure (electronic racks)
- Check single rates at the location of the tagger microscope
- Check single rates at the location of the tagger broad band hodoscope
- Identify sources of background (scraping) in the hall.
- Check out amorphous ladder controls
- Commission halo pmts located on the electron beam pipe to the dump (i.e. adjust HV settings)
- Change radiators and check relative thicknesses using halo pmts
- Use accelerator harp to determine beam centroid and width
- Use amorphous ladder harp to verify beam centroid, width and halo
Checklist at high current I>?, CW
- Verify proper operation of beam as in low current situation
- Check single rates at various positions in the tagger enclosure (electronic racks)
- Check single rates at the location of the tagger microscope
- Check single rates at the location of the tagger broad band hodoscope
- Check radiation levels in the tagger hall
- Check radiation levels in Hall D
- Check radiation levels in the tagger service building
Abnormal conditions
- High radiation levels in any or all areas of interest
- Accidental loss of power to vertical bend string
- Accidental loss of power of tagger magnet
- Accidental loss of vacuum
Photon beam
Goals
- Determine characteristics of photon beam in Hall D
- Safely deliver photon beam through the hall to the photon beam dump
Assumptions
- Accelerator has qualified the machine protection system (MPS) and the personnel safety system (PSS) for Hall D and the counting house
- Delivery of electron beam through tagger to electron dump has been accomplished
- Operation is assumed CW, but perhaps one should start with pulsed mode
- Amorphous radiator installed with $10^{-5}$ thickness, typical
- Steel blocking photon beam pipe in tagger hall have been removed
- Initially the solenoidal magnet is off
Notes
- We should identify all apertures along the beam line to be aware of possible locations for scraping
Checklist, current I< 100 nA
Location: before active collimator
- Require profile monitor to be installed and operational
- Require active collimator to be installed and operational
- Require halo monitors 1 to be installed and operational upstream of cave wall
- Check that detector elements in Hall D are off and prepared
- Check profile of photon beam exiting the beam pipe into cave
- Determine center of photon beam relative to photon beamline
- Compare with response of active collimator
- Use this exercise to calibrate active collimator response
- Scan the electron beam over the face of the radiator to establish aperture and check that photon beam profile behaves as expected
- Check feedback signals of active collimator to control system. (Once understood, these can be used in real time to correct the beam position on the collimator).
- Study the stability of the beam with and without feedback from the active collimator
- Equalize rates in halo counters located in front of the cave back wall
- Check radiation levels inside the collimator cave
- Establish possible locations for electronics
- Check radiation levels in Hall D
- Check radiation levels in the counting house.
- Determine suitability of delivering beam into the hall before proceeding.
Location: exiting pair spectrometer
- Commission the ladder with the PS converter including the harp
- Require halo monitors 2 to be installed and operational downstream of the PS
- Perform a harp scan using the converter ladder
- Measure intensity and energy distribution of photon beam using pair spectrometer fine and coarse arrays.
- Determine rate sensitivity to movements of the electron beam on the radiator
- Check radiation levels inside the collimator cave
- Check radiation levels inside Hall D
- Measure single rates of detectors (e.g. BCAL, FCAL, TOF)
Location: behind FCAL
- Relocate profile monitor behind the FCAL?
- Verify expected profile (projection of collimator) through the detector
- Verify expected photon beam rate
- Check radiation levels inside Hall D
- Measure single rates of detectors (e.g. BCAL, FCAL, TOF)
Alignment of beam to target
- Install commissioning target and start counter
- Check that photon beam is transmitted cleanly through target cell
- Use start counter rates to verify the photon beam is centered on the target
- Check singles rates of detectors (e.g. BCAL, FCAL, TOF)
References
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