Difference between revisions of "Tagging Spectrometer Shift"

Revision as of 14:10, 9 March 2015

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.

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 Expert Voltages.

This will open a screen with the various voltages. For turning on the microscope, first click on Bias voltages and select "Turn ON bias voltages". Wait until the plot shows that the voltages are at 110V before continuing. Note: this does not bias the SiPMs but provides the necessary voltage for eventual biasing.

Once the bias power voltages have been turned on, turn on the chassis voltage by clicking Chassis then selecting "Turn ON chassis voltages". Wait until the voltages have reached their values before continuing.

The last voltages to turn on are the +/-5V powers. Turn these on only after all other voltages have been turned on. Click on the 5V button and these will turn on.

The SiPMs can now be biased using a script. For general running, open a terminal as HDOPS and ssh to gluon28. Once on gluon28, cd ~/tagm. Enter the following command to verify that all control boards are responding: ./probeVbias -l. This will list all control boards that respond and should range from 8e to 9e in hex (17 total). If any are not present, turn off the 5V power and turn it back on.

Once all control boards are present, issue the command: ./setVbias bias_voltages/Vbias_11111L.dat. This turns on all of the SiPMs in low gain mode. For high gain, replace the L with an H. Each 1 corresponds to a specific row being biased.

In order to turn off the microscope, make sure the actual bias voltages on the SiPMs are off by issuing the command as HDOPS on gluon28: ./setVbias bias_voltages/Vbias_00000L.dat. Verify that each board has the biases set to zero by the command: ./readVbias 8e. Do this for boards 8e through 9e in hex. Once it's been confirmed that all biases are off, turn off the +/-5V power. Wait until these are completely off before turning off the chassis voltages. Wait until these are completely off before turning off the bias power voltage.

If the CSS GUI cannot be used, follow these instructions for turning on/off the MPOD crate and tagger electronics voltages.

To turn on the power supply voltages for the microscope first open a browser and enter the following address: t1-7-top

This will bring up a screen showing the MPOD crate voltages. Make sure that the voltages on channels u0-u5, u100-107 are on. Channels u6 and u7 are unsed and should remain off.

MPOD crate and tagger electronics voltages

Instructions on ELOG

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.

Photon Radiators

Move Amorphous Radiator

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

Perform a tagger harp 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 Radiator Scan GUI to bring up the Amorphous Radiator 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.