High Voltage

The power supplies the CRDCs, the ion chamber and the tracking PPACs are remote controlled and accessible via a TCL GUI running on the dedicated S800 linux PC uxpc2. The GUI can be started by clicking on the shortcut "HV" on the desktop of uxpc2.

The voltages and limits on the current can be entered in the "HV set" and "I limit" fields and applied by pushing the respective button. The "Turn on"/"Turn off" button turns the voltage on (ramps to the set value) or turns the detector off. If the voltage needs to be changed, the new value can be entered in the "HV set" text field and the power supply will ramp to the new set value when the "Set HV" butten has been pushed. The actual read back voltages and currents are also displayed and logged to a file in the current run directory of the experiment if the "Start Log" button has been pushed. To protect the delicate gas filled detectors, the HV will trip when the read value of the current exceeds the limit. The HV is connected to the S800 alarm monitoring system and a voice alarm will be triggered as soon as set and read-back voltage don't match. A screenshot of the most recent HV setting is provided on the "Present Experiment" page in the user section of the S800 web site. Please keep in mind that a change in the drift voltage of the CRDCs strongly effects the drift velocity of the electrons and a new mask calibration has to be done to be able to determine the y position of particles.

The Canberra H.V. power supply model 3002 D used for the object scintillator is located in the crate to the right of the DataU6 central patch panel. The voltage will be adjusted at the beginning of the experiment. This scintillator has to be turned off or put on "standby" when entering the vault due to its sensitivity to light.

The high voltages of the E1 and E2 scintillators of the focal plane are controlled via the C.A.E.N SY2527 power supply in the top rack of the APEX tower in DataU6. The voltages are set at the beginning of an experiment.