You can find details and operating instructions for high voltage on the following:

• VDCs: controlled through an EPICS interface. Open the control window from the SummaryDisplay window by clicking on the blue folder icon under Detector for either Electron or Hadron and select detector. A window HRSE Controls or HRSH Controls pops up. Click on red folder icon in the VDC section abd select High Voltage. Follow directions in window for setting HV.
• The HV of the scintillators, cherenkov, lead glass, and FPP chambers through EPICS.  Open the EPICS controls from the SummaryDisplay by clicking on the PMT HV blue folder and selecting PMT HV.  A main HV control screen will pop up. From this screen you can control any of the HV.
• WARNING: The HV on/off buttons turn the entire mainframe on/off. Use the enable/disable to turn individual channels on/off.
• Alarm note: The HV for the FPP have alarms set. If the HV read is:
• In the range 1750 - 1950 V, all is okay --> voltage is green .
• In the range 1700 -1750 or 1950 - 2000 V, it is slightly out of range --> voltage is yellow .
• Below 1700 or above 2000 V, it is far out of range --> voltage is red .
• If the HV screens show all zeroes or are white spaces then the IOC needs to be rebooted using the following steps.
• Telnet to hallasc22.
• Type reboot at prompt.
• After about five minutes HV reading should return.
• The EPICS alarm handler can be turned on to look for alarms on the HV.
• Where the SummaryDisplay is running open a terminal window.
• Type hvalarms in the terminal window.
• The alarm handler X window should appear.
• If communication is lost, the alarm handler will blink white ; in this case you may check the vt100 monitor to see if voltages are okay.
• If a voltage goes out of range, The alarm handler bar will blink red .
• Most of the alarms seem to be false alarms, but you should check them anyway.
• Click on the red blinking bar to bring up the detailed menu.
• On the left side of the detailed window, there should be a line with two red boxes followed by a name in a box, such as earm , harm , or beamline . Click on the box with the name.
• On the right hand side a detailed list of components in this HV mainframe should appear; find the element with the left hand box red.
• Click on the red box; this should stop the blinking of the red alarm bar .
• Associated with this element is a HV address. Check the channel, using the HV interface, to see if voltage is okay.
• Th HV for the scintillators, Cherenkov, lead glass and FPP chambers can also be controlled through the VT100 terminal in the middle room in the counting house. The hadron arm controls are through HAC13 and the electron arm controls are through HAC5 and HAC6
• At the Local prompt type C HAC13 (or HAC5, HAC6)
• If you get the

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This page content was basically written by Ronald Gilman and updated on May 20, 1998 for e93027 experiment.