Detailed Steps for Tuning In-Flight Beams

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Overview of the steps for In-flight beam delivery

Once steps for degraded beam tuning have been completed and a good focus is found at the RAISOR midplane (Separate detailed sheet for this), the steps below can be used to help guide the identification and tuning of the secondary beam.

  1. Acquire information on primary/degraded beam tunes and prep for beam
    1. Ask for docs from operations on primary and degraded beam TOFs and the charge state and slit scan data to be loaded into BOX
    2. Acquire the final cup/collimator FC currents and any notes on degraded beam transmission
    3. Note down RAISOR slit settings (in particular the midplane vertical slits are key)
    4. Insert detector of choice, make sure HV and preamps are on and daq is alive w/ noise etc
  1. Getting a reference spectrum from the degraded beam (can be done at RAISOR exit or target depending)
    1. Cut back beam by x100 w/ slits (not RAISOR slits) first then insert all available attenuation (~x15 Million) + RAISOR Att if needed
    2. Place beam on detectors and slowly remove attenuation until rates are roughly >100 Hz & <500 Hz
    3. Take ref spectrum - optimize daq params and save the settings file as they should not be changed for the duration of the run
    4. Run the RAISOR midplane slits in to 2 - 3 mm gap and take another spectrum (better to have small slit spacing for BRho scans)
  1. Determine the RF Sweeper(R501)/R401 phases for degraded beam with known TOF
    1. Set primary degraded beam rate to few hundred Hz and get Grafana running
    2. Have operations turn on Sweeper to Voltage=2 and phase=0 to start (R401 is still off)
      1. Note: You already may see a reduction in the beam rate do not increase beam current to get back to few hundred Hz
    3. Set the increment step = 1 degree, operators hold down increment to scan over 360 noting the phase every 10 - 20 degree
    4. Document the phase that transmission is the highest for the primary degraded beam
    5. Do smaller steps of ~1 degreed around the regions of the maxima (should be two that are similar one <180 one >180 deg)
    6. Leave Sweeper(R501) at optimal phase, increase amplitude to 3,4,5,6V to see if improvement in transmission, note the best value.
    7. Set Sweeper (R501) to optimal phase/amplitude
      1. FYI: Phase B is the number that ops has been typically used when referring to the phase
    8. Turn on R401 to phase = 0, amp ~ 1.1 or 1.2 (below 0.9 seems to give it issues locking up)
    9. First scan phase, then scan amplitude similar to Sweeper to find optimal R401 parameters, note the values.
    10. TURN OFF THE SWEEPER AND R401 FOR NOW (or maybe only needs to have V=0??)
    11. Should be back to the few hundred Hz rate as at the beginning
  1. Identify the secondary beam and optimal scale factor
    1. Have a good degraded beam spot in the detectors (SCALE = 1.0), w/ RF Sweeper and R401 OFF
      1. Best to have RAISOR slits set to 2 - 3 mm spacing only (typically they are 5 - 7 mm after RAISOR Proc.)
      2. This can be done either with low primary beam on FCA001 or higher beam and RAISOR x100 or x1000 in (just document)
    2. Input current beam line values into ATLAS RAISOR Scaler Tool (make sure it is for the appropriate beam line)
    3. Incrementally scale the RAISOR / beam line magnets in 0.5-1% steps (up or down depending) until 1% or so past expected scale value
      1. At each step, remove attenuation to achieve the 100-500 Hz rates and searching for the beam of interest
      2. Take a fixed time run with the daq to note rates / purities
      3. Generate cuts at each step to track the movement of the beam charge states etc. if needed
      4. Identify the isotope of interest based on calculated energies or previous production of the isotope
      5. Calculate the rate of the isotope of interest as the pps / pnA [note: pnA value from FCA001 divided by q of primary beam]
  1. Optimize the secondary beam
    1. Set beam of interest to optimal scale factor
    2. Put max current on FCA001 and RAISOR att in if needed (essentially as close to primary beam maximum on target as possible)
    3. Carry out procedure for optimizing the RF Sweeper and R401 as described above [Determine the RF Sweeper(R501)/R401 phases for degraded beam with known TOF]
      1. There are a few options at this step:
        1. The RAISOR midplane slits may be opened to 5 - 7 mm gap if the purity is good enough prior to the phase scans
        2. Otherwise, the slits may be opened after finding the optimal settings for the secondary beam to see if rates are increased
        3. Finally, if secondary beam rate is too low relative to the total rate for a manual scan, we can calculate the expected phase and search nearby this theoretical value
    4. Leaving the Sweeper / R401 settings at the optimal values, provide rates / purities etc. to operators for optimizing on the total rate
      1. Keep track of primary beam current at various points through tuning, RAISOR POC needs to help determine with discussions on ops/user sides when to stop tuning
    5. Once rates have been achieved, move to any other optimizations, i.e. beam spot etc.
  1. Document and Monitor
    1. Note down RAISOR settings when needed
    2. Keep track of gas-cell temp pressure when applicable
    3. ...


Definitions

  • primary beam - the beam species and charge state taken out of the source at the ATLAS energy requested
  • degraded beam - the same beam species as the primary beam but at a different (lower) energy and most likely different (higher) charge state
  • production target - the target put in place before RAISOR, e.g., Be foil or Gas Cell
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