Electron Detector

Standard Running Procedure

These instructions should be followed religiously, without exception. The person using beam time alloted for e-detector, should everytime take a print-out of the following procedures and follow it to every step. If any of the following procedure can not be followed due to any operational trouble, an hclog entry should be made

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With the previous beam activity ongoing (parasitically)

• take a quick CODA run to check DAQ functionality
• check analyzer functionality
• from any cdaq machine, from the directory ~/compton/ execute StripTool edetectorEpics.stp . This pulls up the strip chart of some relevant epics variables for e-detector. If you are unable to locate this file, the following epics variables should be explicitly opened.
  • 4 Hall-C Chicane BPMs
    • 3P01A (IPM3P01A.XPOS , IPM3PO1A.YPOS)
    • 3P02A (IPM3P02A.XPOS , IPM3PO2A.YPOS)
    • 3P02B (IPM3P02B.XPOS , IPM3PO2B.YPOS)
    • 3P03A (IPM3P03A.XPOS , IPM3PO3A.YPOS)
  • Rates on Scintillator (cComptScintRateNorm) on the Compton laser table, along with Photon detector Rates (cComptPhotonRateNorm)
• Turn on the HV on the e-detector planes. (Current operating voltage: plane-2: -260V, plane-3: -360V, plane-4: -360V)

Request beam to be set through the chicane, with FFB turned ON

• Check Chicane view: on any cdaq machine type edmmonticello, from the Monticello screen
  • open Magnets -> Magnet Commander
    • 3C -> Compton Combo
    • In this Hall C Compton Control screen, the REQUESTED and ACTUAL current readbacks should be ~104 A
  • open BPM -> BPM Overview
    • open Absolute -> on the Hall C column from the left bottom of this screen
    • BPM 3P01A, 3P02A, 3P02B and 3P03A should have finite non-zero read back
• Check compton rates from the photon detector (typically 600 per uA per second)
  • If the Scintillator rates are too high (> 2000 Hz/uA), DO NOT proceed without talking to an expert from photon detector group.
  • The Fast feedback has been observed to give lower background rate, the status of FFB can be checked on the HALL-C general tools screen on the main-monitor of HALL-C

Request beam to be taken off, for lowering the e-detector

• Lower the e-detector to a position in accordance with current run plan
  • Motion mechanism [[1]]
    • ensure that the beam is turned OFF on request and not by chance before moving the e-detector
    • begin with the program Go Home
    • jog to the intended position
    • Request beam according to the intended run plan

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Backout Procedure

1. Request Beam-off before carrying out e-detector motion. There should be no beam during detector motion
2. Turn OFF HV
3. Retract the detector to position defined as Go Home
4. Retract further to position defined as Garage
5. make hclog entry to inform completion of the intended studies, with any quick conclusion which are obvious

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courtesy: Thanks to Dave Gaskell for the motivation to organize this information

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