Switching Modes

In the process of editing and updating this page. Please contact Juliette Mammei crowder@jlab.org with questions or suggestions.

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

Counting to Integrating

1. Setting HV - this is important
   • VDC HV off. This is important.
   • Scintillator HV off. This is important.
   • Info about detector HV

1. • Adjust Quartz Detector HV for Integrating mode.
2. Switching to High-Current Integrating Mode
   • Septum off
   • Take access.
   • Expert to do the switch of the detector signals to integrating mode
   • Cavities: take out amplifiers. Put in attenuator on BCM. This is important.
   • Set up cavities pre-gain and phase using established values.
   • Septum on
3. Set Up Beam
   • Do the beam recovery procedure
4. Take data ! Check all data including cavities.

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 cavities in integration mode and counting mode at high current. Run analysis macros. Do they work ?
   • 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
   • Septum off
   • Take access.
   • Expert to do the switch of the detector signals to counting mode
   • Switch cavities to have amplifiers. Take out attenuator on BCM. Note: Cannot exceed 2 uA with amplifiers in place.
   • Set up cavities pre-gain and phase using established values.
   • Septum on
3. Set Up Beam
   • Do the beam recovery procedure.
   • Establish 50 nA on Pb target (or whatever current on another target). Normally with laser attenuator = 65 and slit = 13, and then some adjustment to get rates low.
4. Setting HV
   • Do NOT turn on scint or VDC HV yet ! Must establish rates first.
   • Info about detector HV
   • Turn on the HV for upper scint and S0 (if S0 is in place).
   • Adjust Quartz Detector HV for Counting mode.
   • VDC HV on (4 kV) if the T1/T5 rates are below 500 kHz. If above 500 kHz do not turn on HV.
5. Take CODA run and analyze it as usual.