[Halld-tracking-hw] [CDC] preAmps with premixed gas

[Yves Van Haarlem]

Hi All,

Results of Fe-55 measurements with new and old preamps are shown in

http://www.jlab.org/Hall-D/software/wiki/index.php/PreAmp_tests_with_premixed_gas

It looks like:

1/ The new preamps gain is a factor of 2 lower (finally!)
BUT the dynamic range of the new preamp is also a factor of 2 lower so 
in the end we do not really gain anything.

The plan is to take cosmics at 1450V (working voltage determined with the 
old preAmp for 90%-10% Ar-CO2) and see if we can bring the pedestal cut 
down. 2nd step is to lower the voltage in steps of 25V and see if we can 
reach the dynamic range we need in this way (this boils down to determine 
a new efficiency/hv plateau curve). We assume we have better noise 
conditions.

A bottle of premixed 50%/50% Ar/CO2 has been ordered and should be in next 
week.  We will try to figure out what is wrong with our gas mixing system 
in parallel.

Cheers,
 	Yves


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                          /   Yves Van Haarlem
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