Beam Centering and Raster Calibration

<<SBS Main<<HOW_TOs (Beam Line)

GMn Contact Information

Hall A Phone Book

SBS Shifters Wiki Info

Documentation

HOW TOs for shift crew

Expert Tools

Configuration

1. Magnets: BB, SBS, and corrector magnets are ON. See the procedure to ramp up the BB magnet. Accelerator will ramp up the SBS and corrector magnets.
2. BigBite Preshower, Shower (collectively BB CAL), and Hodoscope HV is ON
3. GEM HV remains OFF until we have good knowledge of the beam position
4. DAQ: CODA configuration GMN1. Prescales ps1=0 (BB CAL trigger), all other triggers are turned off (set to psX=-1).

Procedure

1. Check GEM HV is OFF and BB HV On(includes Preshower, Shower, and Hodoscopes)[1]
2. Ensure the target is empty/OUT of the beam path. BigBite and SBS magnets are at zero field.
3. First MCC centers the beam on the differential pumping (DP) apertures (0.75") and then delivers to the beam dump using the dump viewer.
4. Determine the intrinsic beam spot size by performing a HARP scan. Ask MCC to take harp scans on Harps A and B (IHA1H04A and IHA1H04B) and ask them to post the results to our logbook Halog. When the results arrive fill in the green blanks in "Beam spot size at target" section of this spreadsheet and report/halog the values of the spot size calculated which show up in the red blanks. If the average of the Xsigma and Ysigma spot radii (1 sigma) is significantly less than 100 microns. Call the RC and ask what to do. We take a run simultaneously (not necessary, but helpful). Compare BPM EPICS readings to HARP locations. Steps + script?
5. Ion chamber calibration on empty target position. This calibrates the dump ion chambers.
6. Ion chamber calibration on Optics 5-foil target. This calibrates the ion chamber at the target for our optics program.
7. Establish nominal 4x4 rastered beam.
8. Call MCC to stop the beam and request to move to the Carbon Hole (2-mm) target into the nominal beam path
9. Call MCC to request 1 uA of 4x4 rastered beam. Run the DAQ to take data. Analyze the data and produce raster X/Y plots by running the command spot_pp [run_number] [height] [width] from the a-onl@aonl2 account, where height and width are the raster size in MCC units.
10. Using the 2mm hole in the X,Y raster plot to calibrate the size of the raster and position of the hole. Iterate with MCC to center beam on the raster pattern by requesting beam position movements on the harps 1H04A and 1H04E. To calibrate the size of the raster, change the raster size until the X/Y raster plot is about twice the size of the hole. You should now have a beam centered on the target and a 4x4 raster. Record the positions as the new target lock location.
11. Ask MCC to set the raster to 2mmx2mm by dividing the 4mmx4mm units by 2. Take a new run to verify that the Carbon hole fills out the entirety of the plot produced by the spot_pp program. Record these values as the calibrated raster set units.