Difference between revisions of "Beamline"

Revision as of 22:31, 18 April 2015

Initial BPM/Raster checks/Beam centering [3-4 hours]

1. First MCC centers the beam on the beam dump using the ion chambers.
2. Establish CW beam.
3. Note that we will NOT be going through the Compton chicane.
4. Insert the Carbon hole target and ask for 5 μA of 2x2 rastered beam.
   1. Verify that the raster is approximately centered on the Carbon hole target. If it is not, ask MCC to move the beam position in x and y until the hole is roughly centered on the raster image.
   2. Use both HRS DAQs to do the above procedure.
5. Superharp Scan with Raster off
   1. Scan the two superharps (1H03A and 1H03B) near the target with raster off. Make sure MCC obtains two pictures including the three wires for each harp. They should post these images to their ELOG.
   2. Make sure the three wires are clearly visible and have reasonable resolution: ~ 70-200 μm.
6. With at no more than 5 μA of stable unrastered beam find the center of the target using the steps below:
   1. As an example, look at Halog entry # 3307901.
   2. Before starting the procedure, begin a CODA run and leave it running.
      
   3. Run beam with the target in the HOME position, while checking the Left HRS (T1 trigger) and ion chamber rates. Record these rates.
      - The dump ion chamber rates can be found on the "EPICS Computer". See Halog entry # 3308127.
      - The right ion chamber will probably not see the beam, so only focus on the one that does respond to beam.
      
   4. Move the target to the Carbon position. Then have MCC restore beam.
      - Check the rates in the HRS (T1 trigger) and ion chambers. Record these rates.
      - If you can see a difference in rates between the foil and no foil, then continue. Otherwise contact the run coordinator.
      
   5. Move the target to the Carbon hole position. Then have MCC restore beam. The hole in the Carbon foil is 1 mm in diameter.
      
   6. Run beam and see if the rates match step 1) or 2). Record these rates.
      
   7. Have MCC move the unrastered beam around in ~1 mm steps and continue to record the rates along with the associated beam position.
      
   8. Continue step 5) until you have mapped out the location of the hole. If you need, you can have MCC move the beam in smaller step sizes.
      
   9. Stop the run, and make a detailed Halog entry with the above position scan.
      
7. Check the raster size using the spot++ tool (see how-to spot++):
   1. Insert the Carbon hole target to center the beam position with respect to the hole.
   2. Have MCC setup the raster to 2*2 mm², use spot++ to check if the beam is centered around the hole. Move the beam if necessary, but do not increase the raster size. If you cannot find the hole with the raster ON, please contact the run coordinator (Contact information is on the white board).
   3. Make sure you make a log entry with the results of this step.

Raster calibration, spot++

BPM Calibrations (Bullseye Scan) [1-2 hours]

How to perform a bulls eye scan:

1. You need unrastered beam:

    - caution you should not do this with a target requiring rastered beam
    - use carbon, BeO, optics, or in the worst case empty instead

2. Ask MCC to steer the beam to the nominal center of the target.

3. Wait until beam is stable and have MCC perform a harp scan for the two superharps near the target (1H03A and 1H03B) and take a CODA run during the same time. Start the coda run first before asking MCC. Request MCC to make an ELOG entry with the results, you should see all three harp wires. Record ELOG entry numbers.

4. Ask MCC then to steer the beam to positions around the nominal center:

    - cover at least the area the raster will cover: (2,2), (2,-2), (-2,-2), (-2,2) and repeat (0,0)
    - repeat harp and CODA runs for each position

5. Record Harp scan run numbers and corresponding CODA run number for each beam position.

6. Make a record of the harp scans and CODA runs in the HAlog.

How to analyze the bulls eye scan:

 - detailed instructions can be found at the Analyzing BPMs website.
 - the shift crew is not expected to analysis the bulls eye scan.

Superharp Scan with Raster off/on

1. Scan the two superharps near the target with raster off. Obtain two pictures including the three wires for each harp.
2. Make sure the three wires are clearly visible and have reasonable resolution: ~ 100-200 μm.
3. Repeat with raster on. In this case, you may not see the wires clearly.
4. Make sure to post the results in the Hall A electronic logbook or Halog.

BCM Calibrations [2 hours]

1. Warn MCC a few hours beforehand.
2. The Hall A BCM and scalers need to be cross-calibrated to the Faraday cup and a BCM in the accelerator (OLO2) and the Hall A Unser.
3. Before beginning the procedure, make sure the Hall A BCM logger is started, which will record the signals from all relevant BCM used during the calibration.
4. Also start a HRS run to record the scalers during the calibration procedure.
5. It is useful to have someone over in MCC to help coordinate the calibration with them.
6. Take data on carbon target with I = 10, 20, 30, 40 50, 60, 70, 80, 90, 100 μA (or as high a current as available).

ARC Energy Measurement [? hours]

1. The procedure will be conducted by Doug Higinbotham in coordination with MCC.
2. Notify Doug and MCC a few hours beforehand to make sure they are ready and available.