PITA scan HOWTO

• If a production run is going, end the run
• Turn Parity feedback off by doing ctrl-c (or ctrl-\) in the terminal running feedback. If feedback is stopped, runbird will show that Vpita has stopped changing every 10sec. (for details see Parity feedback HOW-TO)
• Make sure beam modulation is not in the middle of a cycle (FFB should be unpaused and the terminal where BMW is running should say it's done with a cycle). Then turn off beam modulation by doing ctrl-c in the terminal.
• once Parity feedback is stopped, call MCC and request the Rotating Half Wave Plate be set to 500. The parity alarm will go off. This is ok.
• Start a new run and label it "Parity Scan" and in the comments say "PITA scan, RHWP=500"
• Do the following to run the auto-mated PITA scan (PITA scan)
  • ssh apar@adaq1
  • cd ~/yufan/scan
  • /scan.py pita
• The auto-scan should take a just few minutes (so long as the beam is >67uA) and the PITA scan will set Vpita +-1000counts or so. You'll be able to see Vpita change in the terminal, in runbird, or in the Parity RTP Screen.
• When the script ends, the terminal will stop outputting text and Vpita should have returned to its orginal value.
• Call MCC and request the Rotating Half Wave Plate be set back to 1.
• Go to the Parity alarm handler and make sure all the alarms have been turned back on and are reading green.
• Restart Parity feedback in the terminal by typing ./feedback_ana (see https://prex.jlab.org/wiki/index.php/Parity_feedback_and_Analysis_Minder for help). Make sure it's running by checking that Vpita changes every 10sec
• Turn beam modulation back on. Do the clear command in the BMW terminal, then do the BMW command as per instructions here How to run
• End the run. Start an new production run (remember to set the run type to Production and remove the comment about "PITA scan")