Compton

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The Hall A Compton

The Compton polarimeter is used to (non-invasively) monitor polarization of the incoming electron beam. It has three major components: an optics table with a laser that can lock to a Fabry-Perot cavity, an electron detector, and a photon detector to count scattered electrons and photons, respectively.

Last edit: LThorne 02:08, 24 February 2016 (UTC)


Shift Workers' Operation Guide

Start a Compton run every two hours.

The Compton DAQ is located in the back room in the Counting House. All commands are done from compton@compton.

If CODA is not already running:

Kill CODA first, then start it up again:
   $ kcoda
   $ startcoda
A few new Terminal windows and a GUI pop up.
LT CODAgui.png
Let "top" refer to the bar with named menu options near the top of the GUI (ex: Platform, Sessions, etc). Let "bottom" refer to the bar below "top" that contains a line of buttons (hover over them to reveal their labels; starting with "Configuration" on the left).
  1. In top, select: Platform > Connect
  2. In bottom, click on "Configuration" button.
    • If configuration listed in the "Run Parameters" box is not FADC_prod: in top, select Configurations > Cool and change it to FADC_Prod.
  3. In bottom, click on "Download" button
  4. In bottom, click on "Prestart" button
  5. When ready to start run, click "Start" button. Typical run duration: 2 hours. Type in any Start Of Run comments in the box. Click "OK" (even if you left comments blank!).
  6. When ready to stop run, click "End" button. Type in any End Of Run comments in the box. Click "OK" (even if you left comments blank!).

Information for Compton Experts

Troubleshooting

  1. HV on/off? -> Compton#High Voltage Controls
  2. Rebooting components: Compton Reboot
  3. [Experts only]: Correct parameters for run in integratingDAQ.flags and compton.params

Collimator Systems

What the jaws look like when placed at their lowest position, as seen on comptcam2. To view this camera follow this link and login with compton credentials.
  • Primary Lead Collimator
    • Presently left fully open at 20 mm diameter.
    • This is a 10 cm long collimator with inserts which can reduce aperture down to 10 mm or 5 mm in diameter.
  • Synchrotron Shields
    • For PREX-II a single 0.25 mm lead foil (painted) is taped to the front of the photon detector.
  • Compton Jaws
    • Remote access for experts can be found at [1]
    • Note, for the duration of the PREX-II running period, the Compton Tungsten Collimator System ("Compton Jaws") will not be used. It should be left it is's parked position of:
   aperture =   1.5 mm
   y center = -46.0 mm

Detector Positioning System

Date X [mm] Y [mm] Comment
2019-06-17 70 33.5 Visually Centered

Cameras

High Voltage Controls

  • HV Control GUI
    • GUI can only be accessed once per person. We share this GUI with Moller Polarimeter.

LED System (Linearity Measurement System)

  • Will add info on MiniMegan soon

Taking an LED run:

  1. Find parameter file GUI:
   $ cd /home/compton/franklin/
   $ ComptonConfig
  1. Click "Pulser On, Pulser Trigger" on parameter file. Click "Apply", then "Done" to close GUI.
  2. Go to CODA. Start a new run to apply the settings. (This does not need to be a long run. You may end it immediately.)
  3. Start your LED run.
  4. When you go back to normal Compton runs: don't forget to turn the pulser off and do a short run to update the parameter file settings!

Laser System

Real time o-scope signals

Cavity lock camera

Make sure laser flipping is on

Turning off the laser

IOC reboot

Accessing the laser hutch in the hall

Laser and Locking troubleshooting

Software & Data Analysis

Relevant files, scripts, etc.

Run Compton analysis:

In compton@compton:

   $ cd /home/compton/online/CompMon

Run analysis software:

   $ ./compmon <run number, no brackets>

Open ROOT:

   $ root -l /data/cmuwork/rootfiles/Fall2016/compmon_<run number, no brackets>.root

Run desired C script located in CompMon directory.


Some useful analysis scripts:

  • For PREX we should use: /home/compton/online/CompMon/dataQualityCheck.C as our online macro!
    • As of now the way to run it is to navigate to the directory with the file and then running with root -l dataQualityCheck.C\(<run number>,<tests flag>\) We're looking into adding a simplified interface in the near future.

The following macros were maintained by people who no longer work on the compton so use with caution:

  • /home/compton/lthorne/CompMon/plotAsymSpectrum.C: Quick and dirty view of asymmetry histograms, cavity and BCM limits.
  • /home/compton/lthorne/CompMon/buildQuartets.C and buildQuartetsPlot.C: For constructing multi-run asymmetry plots.
    • Run instructions are given in the comments at the beginning fo the file.
  • /home/compton/lthorne/CompMon/BCMCal/calibration<runNumber>,C: BCM calibration scripts for specific runs.
  • /home/compton/lthorne/CompMon/plotAccQuartets.C: plots sum, difference histograms for beam off, laser on, laser off for Acc0, Acc4.
  • /home/compton/franklin/CompMon/plotPulser.C: peek at DAQ pulser channels, including info on 'variable' and 'delta' for channel 13.


Link to list of good Compton runs:

List of runs with comments, so know which ones were not junk.

Juan Carlos Google Docs: Runlist (Email Juan Carlos if you want to granted write permission)



Helicity controls

From within NewTools controls (see first few steps in Compton Photon Detector Compton GUI section):

  1. On far right of JTabs menu, there are "master" controls. Find and click on Tools Screen.
  2. Go to the helicity controls. (The default is delayed, so be careful of this.)

Current Scripts

As a brief check, run plotAsymSpectrum.C.

LTRun2565AsymNew.png


Compton Meetings

See last list entry for most recent meeting.

Current Compton Experts

Expert Phone
Dave Gaskell x6092
Alexandre Camsonne x5064
Ciprian Gal x5324
Juan Carlos Cornejo (Photon Detector) x5282

Expert Information

For expert monitoring and troubleshooting information please visit Compton Expert Information.

Analyzer

Code can be found on github: https://github.com/JeffersonLab/HallA_CompMon JC says:

The Makefile is ancient (since it has to work on old systems too) but there is an easy "fix".  In the src/config.d directory, create a file similar to cornejo_compton_jlab.conf but modify the paths respectively. 
Then run ./config config.d/<your_config_file> 
It will update the silly Makefile accordingly

Some old data and examples can be found on

/w/halla-scifs17exp/compton/disk1/data/examples

Old Compton page (pre-Spring 2016)

See Pre-Spring 2016 Compton


Last edit on 2019 06 25, by Ajzec