Tagging Spectrometer Shift

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Tagger Hodoscope

The tagger hodoscope consists of 218 scintillator counters which are installed behind the focal plane of the tagger magnet. The light produced in each counter is detected using Hamamatsu R9800 PMTs which are instrumented with JLab's custom designed dividers and divider-based amplifiers. The PMTs are operated at around 950 V. The hodoscope will be used for tuning the orientation of the radiator crystal by measuring the photon beam energy spectrum. This procedure will require involvement of experts and will not be performed by shift crew members. During data taking, the hodoscope will be used to monitor the beam stability.

Routine operation

The shift crew will be monitoring the detector performance parameters such as the counter rate per channel and detector occupancies as part of the routine shift check list. Any hot or dead channels have to be recorded in the log file. If the average counter rate significantly deviates (the range will be specified for each shift) from the expected rate, an expert should be called. In the case an alarm system detects the PMT current trip, the PMT high-voltage will be shutoff. The crew should restore the voltage on the PMT using the GUI interface (see instructions below). If the problem persists the expert should be called.

Control and monitoring of the system is accomplished using the Hall D graphical user interfaces (GUI) to EPICS [1] [2]. A description of how to bring up the GUI screens can be found in Section Slow Controls.

Voltage Settings and Control

All PMT voltages and trip currents will be preset by the detector experts. The HV will be switched on by the shift crew by clicking on 'All HV' button on the GUI interface. If any of the bases fail to set their high voltage a non-expert will first retry clicking 'All HV'. If the problem persists the expert should be called.

Interlocks

Expert personnel

The individuals responsible for checking that the Hodoscope is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the hodoscope 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 Hodoscope system
Name Number Date of qualification
Alexander Somov (757) 269-5553
Nathan Sparks (757) 269-6544 cell: 210 254-0867

Tagger Microscope

The tagger microscope consists of an array of 100 x 5 scintillators which are installed on the tagger magnet focal plane and will be used to monitor the photon beam energy spectrum in the 'coherent peak' region.

Routine operation

The shift crew will be monitoring the detector performance parameters such as the counter rate per channel and detector occupancies as part of the routine shift check list. Any hot or dead channels have to be recorded in the log file. If the average counter rate significantly deviates (the range will be specified for each shift) from the expected rate, an expert should be called.

Control and monitoring of the system is accomplished using the Hall D graphical user interfaces (GUI) to EPICS [3] [4]. A description of how to bring up the GUI screens can be found in Section Slow Controls.

Voltage Settings and Control

For shift workers, follow these instructions for turning on/off the tagger microscope electronics voltages through the CSS interface.

In the GlueX Overview CSS GUI, scroll down on the left side to the Tagger section and click TAGM Voltages.

This will open a screen with the various voltages. For turning on the microscope, first click on "ALL ON". Note: this does not bias the SiPMs but provides the necessary voltage for eventual biasing.

Once all power has been turned on click "SiPMs LOW" for low gain. This is the standard production setting.

To stop biasing the SiPMs, select "SiPMs OFF". The power supplies will still be on but no voltage will be applied to the SiPMs.

To turn off the power supplies, select "ALL OFF". This will turn off the power supplies in the proper order.

Note: "ALL ON" should first turn on the bias power supply and then the LV power supplies. "ALL OFF" should first turn off the LV power supplies before turning off the bias power supply.

Expert personnel

The individuals responsible for checking that the microscope is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the microscope 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 microscope system
Name Number Date of qualification
Alex Barnes (570) 242-1844 (cell), x5653 7/1/2014
Alexander Somov (757) 269-5553
Richard Jones