Compton Calorimeter Shift

Compton Calorimeter

The compton calorimeter (CompCal) is an array of 12x12 PWO modules. Light from each module is detected using Hamamatsu R4125 photomultiplier tube, which is operated at the typical HV of 950 V.

Routine operation

The shift workers will need to monitor the CompCal performance using the CSS monitoring GUIs described below. The following parameters have to be checked during routine operation of the CompCal detector:

• occupancy plots discrepancies between the detector occupancy plot and the reference histogram such as 'holes' in the occupancy plot, have to be recorded in the log file and the detector experts listed below have to be notified.
• high voltages in the case of problems with HVs on the detector, an alarm should sound; the shift crew can turn ON and OFF HVs using the HV GUI. If the problem persists the expert should be called. Any operations with HVs have to be recorded in the log file and the detector expert should be notified. The HV parameters, such as voltage settings and trip currents cannot be changed by the shift worker.

CompCal EPICS GUI Screens

The crew should set the voltage on the PMT using the GUI interface (see instructions below). If the problem persists the expert should be called.

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  Fig. 1 EPICS screen to check and set HVs on the CCAL modules

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  Fig. 2 EPICS screen to check and set HVs on two CCAL reference PMTs used to check stability of the light monitoring system

CompCal interlocks

Several interlocks are implemented in the CCAL detector, such as the temperature and humidity controls, light tightness of the detector, etc. The list of interlocks and corresponding settings are presented in the EPICS CCAL environment screen below. Problems with most parameters will result in the automatic switching OFF HVs on the detector modules and can be recognized by the specific alarms from the EPICS system. Detector experts have to be notified in the case of any problems.

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  Fig. 1 EPICS screen with CCAL environment variables and corresponding settings for interlocks.

CompCal LED pulser

The CCAL LED pulser can be enabled using EPICS "COMCAL Led Pulser Control" screen shown below. The typical LED pulsing rate is set to 100 Hz. HV settings on the reference PMTs are listed in the voltage control section of this plot. Note, when HV are set on the reference PMTs, the alpha source trigger (see trigger section of the RootSpy) will be enabled. This trigger is used to monitor the stability of the CCAL light monitoring system. The typical rate of the alpha source trigger is about 100 Hz.

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  Fig. 2 CCAL Led Pulser Control Screen

Expert personnel

The individuals responsible for checking that the CCAL is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the CCAL should be referred to those individuals and any changes to their settings must be approved by them. Additional experts may be trained by the system owner and their name and date added to this table.

Table: Expert personnel for the CCAL system

Name	Number	Date of qualification
Alexander Somov	269-5553 (or phone written on white board)