All the detector elements require the use of high voltage. Hall A uses the LeCroy model 1458 high voltage mainframe with models 1461, 1468 and 1469 high voltage supply cards. There are two 1458s on the Electron Arm and one 1458 on the Hadron Arm. The high voltage supplies for the detectors are located in an equipment rack on the upper electronics platform of the Detector Support Frames. One 1458 mainframe is installed in the Beamline equipment racks.
Currently the control of the supplies is realized through an RS-232 serial line connected to a terminal server. Using this readout the high voltage supplies can be controlled from any VT100 style terminal which is also connected to a terminal server on site. The supplies have proprietary software to generate an updating display on a VT100. This display allows relatively easy control of the supplies' settings.
Local control of the high voltage supplies is limited to a PANIC OFF switch, a local HIGH VOLTAGE ON/OFF switch and a key operated, crate AC power switch.
The high voltage power supplies are Class 1 devices and CEBAF policy regarding restrictions will be found in section 6230 of the CEBAF EH&S Manual.
High voltage cables used are red jacketed RG59 coaxial cables terminated in SHV style connectors. The center conductor of the cable is at high voltage while the outer braid is maintained at ground.
