E158 Run III Polarimetry Checklist

 

**Many items have changed since Run II; follow this checklist carefully.

**Print out checklist and check off items as you go along.

**When completed, file checklist and analysis printout into Polarimeter Binder.

SETUP:

·         Check with CryoTech and MCC 5 minutes in advance of starting procedure to verify that this is a good time to do the measurement.  Anticipated time for setup, data-taking and recovery is 45 minutes. The beam needs to be at 10Hz for 45 GeV. Polarimetry runs are performed with full current.

·         Call MCC to inform them that you will suppress beam for setup

o        Request MCC to setup for 10Hz beam.

·         Check with Run Coordinator whether or not the half-wave plate should be toggled.

·         Verify that wire array is in the OUT position. (if not, take it out)

·         Notify the cryo-tech, and put the LH2 target into the OUT position.

o        Consult the E158 Target OPS. Manual and go to the green-tabbed procedure for moving the target out of the beam.

o        Make sure to put the heater mode to “MANUAL” in the Target Heater Control window of the target control (labview) program after raising the target out of the beam.

·        Move 3CM8 collimator and tungsten blocks to their OUT positions.

o        For the tungsten blocks, the “OUT” position is 50.0 cm.

·        Verify that 3QC1A is OUT (will remain out at all times).

·        Make sure the screens 3PR2, 3PR3, 3PR4 are OUT.

·        Put IN the 20 um polarimetry target foil.

·        Turn on the 3T0 Helmholz coils.

o        Follow operating procedure for 3T0 power supply (posted on Rack 54) to turn on supply and set operating current,

o        WARNING ! You must follow this procedure carefully.

o        The supply is unipolar. Any request for polarity reversal must be cleared by the run coordinator (M. Woods or MO) and performed by authorized persons (T. Tuck or MO).  

·        Place the polarimetry detector (scanner) at  Y = 21.0 cm.

·        Check that polarimetry detector HV is 700 Volts.  If not, set it to this value

·        Quadrupoles are to be left at their current production settings.

o       Be sure to clearly label the quad values in the run sheet.

 

 

·        Do FBANAL setup for the (new) halfwave plate configuration. (only if required)

o        set CP, PS voltages appropriately

l/2 State

CP

PS

 

Right

Left

Right

Left

 

IN

2398

-2725

-313

-316

 

OUT

2302

-2821

-190

-193

 

o        reset and clear data for feedbacks (Intensity and Position)

·        Call MCC to check that they are ready to give 10Hz beam and that the wave plate was set correctly.

o       Verify wave plate setting with FBANAL Feedback Configuration Display. 

·        If MCC is ready, unsuppress beam.

 

MEASUREMENT:

  • On the DAQ toolbar, click on the Calibrate button and start a Polarimeter Run.  
    • Please type HV and coil current into the comment block on the run sheet.
    • Collect ~5K beam events at 10Hz  (Note: 5K events at 10Hz beam should take about 10 minutes.  The number of interrupts follows the DAQ rate, not the beam rate.  So may have 60Hz DAQ and interrupt rate, but only 10Hz beam rate.  See the “Trigger Rate” stripchart to verify beam and DAQ rates.)
  • Bring up polarimeter detector stripchart display for raw values from the scaler fast menu.  Verify that have ~800 adc counts.
  • Remove the foil target and take a no-target polarimetry run.
    • Collect ~1K beam events at 10Hz.

RECOVERY:

  • When ready to go back to production data, call MCC to inform them that you will suppress beam for recovery
    • Request MCC to set up for 120Hz production running.
  • Move wire array to the IN position (if it is to be used.)
    • Take two production runs with wire array in, then remove.

 

 

  • Notify the cryo-tech, and put LH2 target to IN position.
    • Consult the E158 Target OPS. Manual and go to the green-tabbed procedure for moving the target into the beam.
    • Make sure to put the heater mode to “AUTO” in the Target Heater Control window of the target control (labview) program after lowering the target into the beam.
  • Put 3CM8 and the Tungsten blocks IN
    • Tungsten block 1 should be at 25.5 cm, block 2 at 25.0 cm.
    • The detector wheel should be at zero degrees.
  • Turn OFF the Helmholz coils.
    • Follow operating procedure for 3T0 power supply (posted on Rack 54) to turn off supply. Warning! You must follow this procedure carefully.
  • Verify that the polarimetry target foil mover is in the “Physics Running” position.
  • Retract the polarimetry detector (scanner) to 50 cm. (Note:  HV now stays ON.)
  • Call MCC to check that they are ready to give 120Hz beam.
    • Verify waveplate setting with FBANAL Feedback Configuration Display 
  •  If MCC is ready, unsuppress beam.  

Data Analysis:

On a noric CPU, from any account with the MayDay setup open two windows, one for running the analyzer, another for running PAW. Let us assume we have a polarimetry (foil) run NNN1 and a background (no target) run NNN2 to analyze.

 

In the 1-st window:
    noric04$ cdPol
    noric04$ run.pl  
NNN1

** In case of problems please contact Yury . **

In the 2-nd window:
            noric04$ cdPol
            noric04$ cd paw_2003
            noric04$ paw

PAW> exec   run   run=NNN1
            PAW> exec   run   run=
NNN2

PAW> exec   checku  run=NNN2   helmh=84.0  hv=700 (analyze the bkgd. run)

Before analyzing the foil data, wait for the background to finish and look at the output. Look for a line that reads something like: signal/tor: 29.78 +/- 0.02  This is the background subtraction that you will put into the actual foil analysis:

 

PAW> exec   checku  run=NNN1   helmh=84.0  hv=700  bgnt=29.78

The last command will analyze the run, subtract the background and print useful information. In case the signal saturates or is close to saturation it would suggest the HV to use. These are a good example of the output plots and  a bad example (saturation).

Documentation:

Make sure to document carefully in the polarimetry run sheets the HV used, the coil current (84A at 22.5V), the rep. rate of the beam (10Hz, not the 60Hz DAQ rate), and the quadrupole settings (typically nominal).

TIPS for the PAW analysis:

Storing the picture in a local file paw.ps and printing it:
    PAW> opla
    PAW> exec   check_1   run=
NNN1   hv=700   helmh=84.
    PAW> clops
    PAW> prpc1

About 20 runs can be attached at the same time. One can also check the logical units by:
PAW> ld  // and use PAW commands to read the ntuple and fill histograms using the appropriate unit.

Detector Y(R)-scan:
    PAW> exec   yscan   run=
NNN1

Target position scan:
    PAW> exec   trg_scan   run=
NNN1

In case of problems please contact Eugene or Yury.
Note: The analysis procedure above is crude, with a purpose to make sure the data are good. The next step would be the background subtraction procedure. It will be added later.


Last Updated: July 28, 2003 by MO and Woods  http://www.slac.stanford.edu/exp/e158/documents/PolMeasure.html)

Robert Michaels   --   e-mail: rom@jlab.org

 Eugene Chudakov   --   e-mail: gen@jlab.org