2-pass commissioning

Beam Commissioning at 2-pass for Fall 2019

Beam checkout

For polarized 3He running in Fall 2019 and Spring 2020, the nominal raster for production is 5mm diameter circular. The nominal triggers used are 3/4 for both HMS and SHMS. No coincidence trigger will be used/setup.

Establish beam in the hall

  Goals 
 - Using empty target location, make sure beam reaches beam dump without hitting anything. 

Initial Raster checks

  Goals 
 - Establish beam to be roughly centered in beam pipe by locating it on YAG viewer just upstream of target.
 - Turn on Raster and verify beam profile expands as expected.
   
  Setup 
 - Beam Current:   Viewer limited (Tune Beam)
 - Target:         Empty
 - Raster:         Off; 5mm diameter

 Procedure
 - Insert YAG viewer on Hall C superharp girder
 - start with raster off, verify beam spot roughly centered
 - if the beam energy has changed, check that on the Hall C Raster Control GUI it is initialized for the correct beam energy (at the top of the GUI).
 - request raster on:  5mm diameter
 - 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)

  Setup 
 - Beam Current:   5 uA CW
 - Target:         Empty 
 - Raster:         Off

 Procedure
 - Verify that the raster is OFF for the harp scans at the target (3H07) 
 - Ask for harp scans with IHA3H07A and IHA3H07B
 - 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, check/confirm raster size

 Setup 
 - Beam Current:   5--10 uA CW
 - Target:         Double Carbon Hole

 Procedure
 - Note:  DAQs should be running and double carbon hole 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 current target configuration (2017--2020) **
 - 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:    Double Carbon Hole
 - Current:   5 uA CW
 - Raster:    5mm diameter
 - Run DAQ on SHMS / HMS
 - Set prescales to ensure DAQ rate is dominated by scintillator triggers (ie. 3/4)
 - Run the online analyzer and look at the 'Fast Raster' panel of the online GUI:
 - Locate the hole in the 2D intensity histogram. A rough z cut should be included in the script to show up- and down-stream carbon hole separately.        
 - NOTE: if the beam energy in standard.kinematics is not up to date, the distance scale on the 2D histogram will be wrong

 - Center Beam on using Double-Carbon-Hole Target:
     - Iterate until the hole is clear, and is centered in the circular raster pattern for both up- and donw-stream carbon foils
       - Adjust beam position
       - Re-run the online analzyer on the new file(s) to see the effect of a raster size change and/or beam position change.  Make sure changes are logged in the CODA start-run entries!
 - Calibrate raster dimensions against (known, typically 2mm diam.???) Carbon Hole diameter by adjusting Raster magnet settings until raster an appropriate size (RC will know).

Target system checkout and commissioning

  Goals 
 - Make sure we can put beam on all target positions. Raster should be ON (5mm diameter) for all settings.
 - This step also serves/completes the basic trigger/DAQ checkout, and tuning of online monitoring scripts

  Setup 
 - Beam Current:   5--30 uA CW, raster always ON (5mm diameter)
 - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
 - Target:         Varies

 Procedure
 - Move target to single foil position, take a 2 minute run at 5 uA and confirm we see one foil.
 - Keep target at single foil position, take a 2 minute run at 30 uA and confirm beam can be set at 30uA.
 - Move target to multi-foil position, take a 2 minute run at 5 uA and confirm we see all seven foil.
 - Move target to reference cell position, take a 2 minute run at 5 uA and confirm we see two glass windows at z=+20 and -20cm.
 - Keep target at reference cell position, take a 2 minute run at 30 uA and confirm the target is still there.

Polarized 3He Cell checkout and commissioning

  Goals 
 - Make sure we can put beam on the polarized 3He cell, commission target polarimetry. Raster should be ON (5mm diameter) for all settings.

  Setup 
 - Beam Current:   5--30 uA CW, raster always ON (5mm diameter)
 - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
 - Target:      Polarized 3He Cell

 Procedure
 - Ask the target operator to do one target polarimetry measurement.
 - Move target to polarized 3He cell position, take a 2 minute run at 5uA and confirm we see events from both 3He gas and two glass windows at z=+20 and -20cm.
 - Stop the beam, ask the target operator to do one target polarimetry measurement.
 - take a 10 (what's the time constant for beam depolarization to set in?) minute run at 30uA, watch the beam ramp rate (confirm it is no faster than 1uA/sec), and confirm we see events from both 3He gas and two glass windows at z=+20 and -20cm.
 - Stop the beam, ask the target operator to do one target polarimetry measurement.

Detector checkout and calibrations

  Goals 
 - to verify PID detectors work properly

 Procedure
 - Because we use 3/4 triggers, PID and ECal calibrations are not crucial at this stage. However, we can use data taken above to do a rough PID performance check for both the Cherenkov and the ECal.

Other

  Goals 
 - What to do if we have finished all above and there is still time left before pass change to 1-pass?

 Procedure
 - We could possibly do optics calibration (need 15 hours total, sieve in). Ask RC!