Beam Checkout Procedures

Basic Beamline, Raster, Instrumentation checkout

Initial Raster checks

  Goals 
   - Establish beam to be roughly centered in beam pipe by locating it on YAG viewer (Hall_C_YAG_Viewer) just upstream of target.
   - Turn on Raster and verify beam profile expands as expected.
   

 - Beam Current:   Viewer limited (Tune Beam)
 - Target:         Empty, or solid target 
 - Raster:         Off; 2mm x 2mm

 Procedure
 - Insert YAG viewer on Hall C superharp girder
   - start with raster off, verify beam spot roughly centered
   - request raster on:  2mm x 2mm
     - watch beam spot on viewer and verify Raster's basic functionality
 - Retract viewer

Harp scans

  Goals 
   -Verify operation of Harp scanners w/ beam.
   - Establish acceptable beam profile (nominal 100--500um sigma)

 - Beam Current:   5 uA CW
 - Target:         Empty, or solid target 
 - Raster:         Off

 Procedure
   - Verify that the raster is OFF for the harp scans at the target (3H07) 
   - Take Harp swipes for all viewers on Hall C beamline
   - verify beam profile (nominal 100--500um sigma) on at least one scanner on Hall C upstream beamline (good to check 3H07A/B)

Target/Beam centering, Raster calibration

  Goals 
   - Establish beam position on target.

 - Beam Current:   5--10 uA CW
 - Target:         BeO, Carbon Hole

 Procedure
 - Note:  DAQs should be running and a solid target is in place
   - Online shift crew will proceed with program below.

 - Attempt to view beam on BeO (if available in target ladder)  ** NOT available in Fall/Spring 2017 **
     - Target:    BeO
     - Current:   5 uA CW
     - Raster:    OFF
   - Target camera: ON
   - Target lamp:   OFF
   - Log camera snapshot of beam spot on BeO

 - Image Carbon Hole target using Raster current pickoffs vs. raw trigger rates in SHMS and/or HMS
     - NOTE: If there are issues with the raster systems, this step can be skipped provided experts are confident that we know where the beam is on target (ie. good BeO snapshot)
     - Target:    Carbon Hole
     - Current:   5 uA CW
     - Raster:    3mm x 3mm
   - Run DAQ on SHMS / HMS
     - Set prescales to ensure DAQ rate is dominated by scintillator triggers
   - Run Spot++
     - View the Raster *Current* X vs Y plots (not BPM plots)
     - Locate the hole in the 2D intensity histogram
       Example of imaged hole:  https://logbooks.jlab.org/entry/3427728
   - Center Beam on Target:
     - Iterate until beam centered in raster pattern
       - Adjust beam position
       - Run Spot++ to view effect
   - Calibrate raster dimensions against (known) Carbon Hole diameter by adjusting Raster magnet settings until raster is just covering the carbon hole in the image.