From: Matthew Worcester (mworcest@hep.uchicago.edu)
Date: Fri May 06 2005 - 21:02:21 CDT
Hi all,
Here are the plots I promised last week.
Attached are the energy spectra (pmtrad_energy.ps) from PMT radiation
(gammas from Tl and Bi decays in the U/Th chain) for oil buffer
thicknesses from 90 cm (baseline) to 20 cm. The setup is a two-zone
detector, with the steel vessel fixed at R = 350 cm. The PMTs are
"point-sources" located 30 cm inside the steel vessel. Thus, the buffer
thickness of 30 cm would have the acrylic vessel just at the tip of the
PMT glass. There are 935 PMTs. The gammas are generated isotropically
with multiplicity and energy determined by BR and then compton scattered
through the oil.
Also attached is the rate in Hz (pmtrad_rate.ps) of the PMT radiation
gammas that leave any energy at all inside the scintillator. This
assumes a 10 decay/sec rate from the Hamamatsu R5912s, which is a number
that they provided a long time ago. We can improve on this with
measurements we have taken of the radiation off of the R5912 tubes that we
have at Chicago.
Cheers,
Matt
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