Pair Spectrometer Shift

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The Pair Spectrometer

The pair spectrometer consists of the converter, the dipole magnet and two types of scintillator detectors: 290 high-granularity hodoscope and 16 low-granularity counters (PSC), which are used to detect e+e- pairs produced in the converter by a beam photon. The converter accommodates up to 3 thin foil targets and a wire, which will be used to study the profile of the photon beam. The magnet will be operated at 1.8 T field. Light from scintillators is detected by SiPMs and Hamamatsu H7415 assemblies for the hodoscope and PSC, respectively. The nominal operating voltage for PMTs is about 1.2 kV.


Checking PS settings

Before starting the run the shift should follow the run configuration requirements and perform the following actions:

  • check that the magnetic field is switched on and the magnet current corresponds to the run configuration requirements. This can be done using a magnet Slow Control GUI. If the magnet is switched off
    • make sure that the photon beam is not present in the hall, otherwise call to MCC (999) and request switching the beam off.
    • switch on the magnet using the magnet Slow Control GUI. Select "Input Select 1" on the main control GUI below the "Setpoint" window. Procedure: Enter 90% of the maximum current (900000ppm, i.e 1238A). Once the current reached, wait 10 minutes so that it stabilizes. Then for the nominal 1.8T setting, go to 720600ppm, i.e 910 A. It will take about 10 min for the field to be stable.
    • Set the Sweeping Magnet to 190 Amps if we want to have the sweeping magnet cleaning up the beam after the collimators.
  • check that the right converter is inserted in to the photon beam. This can be done using the Slow Control GUI. If the converter is not in the right position, the shift crew must call to MCC (7050) and request switching the beam off. The converter can be subsequently inserted by selecting the foil number on the GUI screen and clicking on "GO' button. Green color of the button indicates that the converter is on the right spot.
  • Set high-voltages on the PSC using a Slow Control GUI. Press HV "ON" button on the GUI screen. 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.
  • Set bias and low voltages for the PS hodoscope using a Slow Control GUI. Press HV "All LV" button and "All B'/"All A" buttons on the GUI screen.

Routine Operation

The shift crew should monitor the detector performance parameters such as:

  • rates of the hodoscope and PS counters, and the spectrum of the photon beam. The monitoring should be performed using a Slow Control GUI. 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, the run coordinator should be called.
  • HV and voltage settings for the PCS and the hodoscope using the Slow Control GUI. In the case an alarm system detects the PMT current trip, the PMT high-voltage will be shutoff. 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.
  • temperatures for the hodoscope SiPMs. The alarm will be generated if the SiPM temperature exceeds the critical value. If this happens the expert should be called.

Interlocks

How-To

Run PS Scalers

  1. Login to gluon computer under hdops and use ps_client command to start the pair spectrometer client.
  1. If the client is already running, on the console you will the username and the node, where the ps_client has been started. Login to the corresponding node and kill the

ps_client process. If the process doesn't exist (i.e. the node was rebooted) delete /home/hdops/CDAQ/config/hd_server/ps_client.log file and start the ps_client again.

Move Pair Spectrometer Converter

  1. Open Hall-D CSS EPICS Control if not already available following instructions.
  2. From Main Action Bar, click Motors in BEAM section.
  3. Click PS Converter to bring up the Collimator Control GUI.
  4. Click the button corresponding to the desired location to move the collimator. Wait until the Motor is Done.
  5. If the communication to the motor is broken, e.g. pink fields showing, refer to instructions to reboot the IOC.
  6. Make a log entry to HDLOG.

Perform a Converter Scan

  1. Open Hall-D CSS EPICS Control if not already available following instructions.
  2. From Main Action Bar, click Motors in BEAM section.
  3. Click Converter Scan GUI to bring up the PS Converter Scan GUI.
  4. Click SAVE DATA button to create a new data file.
  5. Type in values for START, STOP and STEP SIZE.
  6. Verify POSITION SETTLING TIME.
  7. Verify the PVs to be saved in data file.
  8. Click SCAN to start a scan.
  9. Watch the progress bar and wait until the scan is finished.
  10. If the communication to the motor is broken, e.g. pink fields showing, refer to instructions to reboot the IOC.
  11. Make a log entry to HDLOG.

Detector Expert On Call

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 Pair Spectrometer system
Name Extension Date of qualification
Alexander Somov 269-5553 June 12, 2014
Beamline expert on call