[Tpe] tagger calibration

[Larry Weinstein]

Dear Volker,

I notice that you have scheduled 4 days for tagger calibration following 
the TPE run.

One possibility for calibrating the tagger is to put direct 300 MeV beam 
thru the tagger, scan the tagger magnet, and use epics to record the 
magnet current and the tagger detector scalers.  We would want to take 
10^4 data points to give 10^-4 precision. At an EPICS data rate of 1 Hz, 
this implies a 3-hour scan. This would need to be done before and after 
removing the tagger detectors.

If the beam is horizontally detuned to 1 mm, a 1 nA average beam current 
would give a tagger detector dose of about 6x10^4 Rad.  To be safe, we 
would want to reduce the current to 100 pA (or increase the EPICS daq 
rate to 10 Hz).  Hari Areti pointed out that the accelerator could be 
tuned at higher beam current and then run for a few hours at lower 
currents.  He also said that repeating an existing accelerator tune (eg: 
362 MeV) would be easier than creating a new one.

I am not a tagger expert so I do not know the other problems with this 
approach.  If you want to do this, the pre-removal run could possibly be 
done this week while all three halls are down.


-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 5809 (fax)
weinstein at odu.edu
http://www.physics.odu.edu/~weinstei