Expert procedures

Compton Procedures (more detailed for experts or enterprising shift crew workers)

General Compton running:
1.At least once every hour restart a new CODA run. CODA should be open on the first desktop of ccomptl1.
2.At least once every hour check the status of the HV. If a trip occurred, see below.
3.Check whether the laser is still flipping (EPICS channel cComptCavityPower).
--> This should be obvious from the camera as well. If not flipping, call an expert. This EPICS PV should be visible on the desktop of Striptools on ccomptl1.

After a photon detector HV trip:
1.Check that the normalized rate on the background scintillator (EPICS channel cComptScintRateNorm) is still below 200 Hz/uA.
--> If not, ask MCC for improvement in beam conditions if no clear isolated event happened. If the scnitillator rate climbs above 300 Hz/uA - we may want to back out of the chicane (consult an expert first). This EPICS PV should be visible on the desktop of Striptools on ccomptl1.
2.If beam conditions do improve and stabilize then wait 5 minutes after the trip and turn on the HV on the photon detector to 1700 V (channel ComptPhoton1).
--> The HV controls should be open on the 3rd ccomptl1 desktop. If not log on to cdaql5 as cvxwrks and cd to $EPSHV/tk then run ./HV_compton.tcl and turn on ComptPhoton1.
3.If the photon detector HV trips again within 15 minutes, leave the photon detector off but keep beam in the chicane.
4.Try to enable photon detector only after consulting the on-call expert or after significant improvement in beam conditions in the normalized rate on the background scintillator.

After a background scintillator HV trip:
1.Make sure HV is off to the photon detector (channel PhotonDet_6).
--> The HV controls should be open on one of the ccomptl1 desktops. If not log on to cdaql4 as cvxwrks and cd to $EPSHV/tk then run ./HV_compton.tcl and turn on PhotonDet_6.
2.Ask MCC for improvement in beam conditions if no clear isolated event happened. If no improvement, back out of the chicane.
3.Five minutes after the trip, turn on the scintillator HV (channel TableScint_7) and if conditions have improved turn on the photon detector to 1700 V (channel ComptPhoton1).
4.If the background scintillator HV trips again within 5 minutes, potentially back out of the chicane after talking to the on-call expert.

Logging into e-Detector HV module

• From any cdaq machine enter

telnet hctsv4 2003

• Don't expect a prompt, press Ctrl+m followed by Ctrl+j to sync the module with the communicating port
• From here one can seek to change or query the status of the HV module. Following are some relevant commands

u1 (voltage readback on channel A of the module)
i1 (current readback on channel A of the module)
d1=400 (setting the voltage on channel A to 400 for ramping up the voltage)
d1=0 (setting the voltage on channel B to 0 for ramping down the voltage)
d1 (querying the set voltage on channel A)
g1 (go to the set voltage on channel A)
s1 (querying the current status of channel A)

• The channel A provides HV to detector planes 1 and 3, while channel B provides HV to planes 2 and 4.
• Similarly, channel B can be queried or set by using '2' instead of '1' in the above commands.

Backing out of the chicane:
1.Make sure Beam is off and the e-detector motion FSD is masked 2.Turn off the HV on the photon detector (channel ComptPhoton1)
3.Retract the electron detector (send to "GARAGE")
4.Ask MCC to restore beam through the straight through section.
5.Keep monitoring the rate on the background scintillator (EPICS channel cComptScintRateNorm)