Switching Modes

To switch between Integrating Mode and Counting Mode for the PREX DAQ.
PREX Main<< HOW TOs

This page details the checklists for switching between counting and integrating modes. For reference, here are the instructions from PREX I. It is critical to do these steps in the correct order, especially for switching from counting to integrating. The detectors which are used in counting mode can be damaged if they are on when the rate is as high as it will be in integrating mode.

Note about voltages

1. Quartz HV are first 2 channels of S1 (2nd card)
2. L-HRS quartz rpi8 .... L1.0 = -905.0; L1.1 = -0; L1.2 = -1100.0; L1.3 = -1100.0 .... integrating mode
3. R-HRS quartz rpi4 .... L1.0 = -910; L1.1 = -0; L1.2 = -950.0; L1.3 = -1000.0 .... integrating mode
4. For counting mode voltages are
   1. RHRS (rip4 - S0 slot)
      • S0A: L0.0 = -1600 V
      • S0B: L0.1 = -1600 V
      • S3_1: L0.2 = -1300 V
      • S3_2: L0.3 = -1300 V
      • S3_3: L0.4 = -1300 V
   2. LHRS (rpi8 -S0 slot)
      • S0A: L0.0 = -1400 V
      • S0B: L0.1 = -1600 V
      • S3_1: L0.2 = -1300 V
      • S3_2: L0.3 = -1300 V
      • S3_3: L0.4 = -1300 V

Do NOT leave RQ3 at 1400 A more than 5 min (but leave it there for 1 min)!!

1. 1. LHRS VDC:- rpi8 - Slot S7 - channels - L6.0 = -3500 & L6.3 = -3500.0 Volt
   2. RHRS VDC:- rpi4 - Slot S14 - channels - L14.5 = -3500 & L14.7 = -3500.0 Volt
2. For the S0 and S3 detectors, we should simply need to turn them on (counting mode) or off (integrating).

Counting to Integrating

1. Turning OFF the HV
   • VDC HV
   • Scintillator HV
   • Adjust Quartz Detector HV for Integrating mode
2. Switching to High-Current Integrating Mode
   • Take access.
3. Set Up Beam
   • Do the Beam Recovery procedure
4. Take data !

Integrating to Counting

1. Preliminaries. to do long before switching
   • Make sure spectrometer DAQ works (might need reboots). Use the CODA guide if necessary.
   • Check with spot++ that rastered size is approx 4 x 3 mm (whatever is our present norm.)
   • Check the beam position ("centered" to within 0.3 mm, using the production criterea, see white board).
2. Switching to Low-Current Counting Mode
   • Take access.
   • Expert to do the switch of the detector signals to counting mode
3. Set Up Beam
   • Do the beam recovery procedure.
   • Establish 0.3 microA on Ca target (or appropriate current on another target).
4. Setting HV
   • Do NOT turn on scint or VDC HV yet ! Must establish rates first.
   • Turn on the HV for upper scint and S0 (if S0 is in place).
   • Adjust Quartz Detector HV for Counting mode.
   • VDC HV on (3.5 kV) if the T1/T2/T6 rates are below 500 kHz. If above 500 kHz do not turn on HV.
5. Take CODA run and analyze it as usual.

Aligenment check without hall access

1. Turn off beam.
2. Set scintillator's voltages as mentioned above.
3. Request MCC for 0.3 uA current, 2x2 raster with 4Ax,4Ex = -0.3 and 4Ay,4Ey = -1.5 target locks and no lock on 1C12.XPOS BPM.
4. Check T1 rate. For the above condition the T1 rate will be around 200 kHz.
5. If the rate is matching and less than 500 kHz, turned on VDCs (HVs channels are mentioned above).
6. Turned on downstream main detector for both arms (rip8 (for LHRS): Slot-S1; Channels - L1.1 = -1900 Volt and rpi4 (for RHRS): Slot S1; channel -L1.1=-1900 Volt).
7. Run counting mode DAQ.
8. Analyse data for 200000 events.
9. Root (prexLHRS_XXXX_200000.root or prexRHRS_xxxxx_200000.root) files are saved inside '/chafs1/work1/prex_counting/' directory in the 'a-onl' account of 'a-onl' machines.
10. Load this rootfile and run the following script '~/devi/crex/alignment/alignDS.C' for both arms. This will generate the alignment plots.
11. If you are not happy with the plots and want to move detectors -call Devi.
12. If everything is fine - turned off VDCs, scintillators and downstream main detector.
13. Now you are ready to go back integrating mode. Call MCC and ask for enable 12C.XPOS lock when they are back with high current.