Electromagnetic Calorimeter Shift
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Contents
Electromagnetic Calorimeter (ECAL)
The Electromagnetic Calorimeter (ECAL) consists of 1596 PbWO4 scintillating crystals organized into an array of 40 x 40 modules with a hole of 2 x 2 modules in the middle for the beam. The ECAL replaces the inner part of the GlueX forward lead glass calorimeter. Light from each module is detected using a Hamamatsu 4125 photomultiplier tube. The detector operates at approximately 17 deg C. Two chillers are installed to cool the calorimeter detector frame, while heat from the PMT front-end electronics (active bases) is dissipated by fans that circulate coolant and blow air over the detector electronics. The detector is equipped with resistance temperature detectors (RTD) positioned on the detector. Temperature and humidity inside the detector room are monitored by four sensors of each type. High voltage for each PMT is provided by a 48-channel CAEN A7030N module, with thirty-six modules housed in three SY4527 mainframes. The maximum HV does not exceed 1300. The PMT amplifier requires +- 5 V power, supplied to the active bases by two WIENER MPOD modules. The typical operating HV for the PMTs is about 1 kV.
Routine operation
The shift workers will need to monitor the ECAL performance using the CSS monitoring GUIs described below. The following parameters have to be checked during routine operation of the ECAL 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 and low 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.
ECAL 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.
Fig. 1 EPICS screen to check and set HVs on the ECAL modules
Fig. 2 EPICS screen to check and set HVs on two ECAL reference PMTs used to check stability of the light monitoring system
ECAL interlocks
Several interlocks are implemented in the ECAL 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 ECAL 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.
Fig. 1 EPICS screen with ECAL environment variables and corresponding settings for interlocks.
ECAL LED pulser
The ECAL 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 ECAL light monitoring system. The typical rate of the alpha source trigger is about 100 Hz.
Fig. 2 ECAL Led Pulser Control Screen
Expert personnel
The individuals responsible for checking that the ECAL is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the ECAL 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.
| Name | Number | Date of qualification | |
|---|---|---|---|
| Alexander Somov | 269-5553 (or phone written on white board) | Nov. 10, 2024 |
