[Tpe] Tagger calibration

[Larry Weinstein]

Dear Folks,

One possibility suggested by Dave Kashy (with modifications from Stepan 
and Eugene) is to use the primary electron beam to calibrate the tagger.

   1. Put a 300 MeV pulsed low-current electron through the tagger magnet
   2. Sweep the magnet field slowly.
   3. Read out the tagger detector scalers and the tagger magnet current
      in epics.
   4. Correlate the magnet current with the location of each of the
      tagger detectors.

After the TPE run, when we have replaced the detectors, repeat the 
procedure to determine the precise locations of the detectors.

According to Arne, it would take about 12 hours to configure the machine 
in this way.  It would take an hour or two to do the measurement, so the 
total time required would be less than one day of exclusive beam (ie: no 
other expt can run during this time).

If Qweak is willing to let us do this, we can do this before the summer 
shutdown.  Alternatively, if Primex runs before TPE, we could do this at 
the end of the Primex run.  It would be better do this before the summer 
shutdown to allow us the flexibility of removing low energy tagger 
counters during the summer shutdown (assuming that Primex won't use them).

Note that this assumes that TPE will run this fall.

-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
weinstein at odu.edu
http://www.lions.odu.edu/~lweinste/

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