Beam Line Detectors Shift
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 will be 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 and check PMT high-voltages. Hot or dead channels have to be recorded into the log file.
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.
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 signature added to the document residing in the Hall D Counting House.
| Name | Number | Date of qualification |
|---|---|---|
| Alexander Somov | (757) 269-5553 | |
| Franz Klein |
