[Halld-cal] Fwd: 1.2-V vs 1.4-V calibration of BCAL

[Elton Smith]

-------- Forwarded Message --------
Subject: 	1.2-V vs 1.4-V calibration of BCAL
Date: 	Fri, 5 Feb 2016 17:14:01 -0500 (EST)
From: 	semenov at jlab.org
To: 	wmcginle at andrew.cmu.edu
CC: 	elton at jlab.org, zisis at uregina.ca



Will:

I made a comparion of the calibration constants (NSA=55,NSB=-5) for 1.4-V
overbias (end-of-2015 cosmic data) with the ones for 1.2-V overbias
(end-of-2014 cosmic data) - see the plot in the attachment. It looks like
the factor is about 0.78-0.79 that is smaller than "gain
ratio"=1.2/1.4=0.86 (viz., PDE is affected indeed) but bigger than the
0.69 factor that you used before.

The right tail on "Downstream" histogram is (probably) the result of
imperfect  1.2-V calibration because of relatively small signals and
relatively small statistics.

Just in case if you are interested...

Thank you,
Andrei


> ...
> For your "new" results are you using data with SiPM over bias at 1.4 V or
> 1.2 V? We changed the over bias from 1.2 V to 1.4 V when we went from the
> Fall run to the Spring run period and I don't think we changed it back for
> the cosmic runs after that, but most of the cosmic data taken from Fall
> 2014 and earlier was set at 1.2 V over bias. My constants that I put in
> ccdb Nov. 16 were using the Spring data at 1.4 V over bias. When I
> compared my gains that I extracted in Fall running (1.2V over bias) to the
> Spring running (1.4V over bias) I had to multiply by a factor of 0.69 to
> go from Fall to Spring, that might explain some of this.
> ...
> Will



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