From: Chris Tunnell (tunnell@mail.utexas.edu)
Date: Thu Apr 27 2006 - 20:37:26 CDT
Stan is correct, I just added a 'for loop' from 0 to Npmt on some array in ReactorFsim that stored PMT locations, and then dumped the coordinates to a file. You can see the file in CVS at data/pmtcoordinates_spherical_id.dat. There are also scripts in the util directory to go from that format to RATDB. I don't remember changing the coverage, so I don't know why it is off, but this was nearly a year ago.
Currently, the 20 cm from the tank distance seems right in RAT (though the part of the PMT the measurement is made from could be different), but the number of PMTs is too high. We have 27% coverage instead of 24.35%. This has been a known problem for a while, but nobody really knew specifics about the coverage other than 25% when asked, so I made a ticket in RATTRAC about it:
http://nu.ph.utexas.edu/bw/trac/ticket/36
If you could close that when you figure it out. It sounds like you would benifit from adding a feature to RAT that did what ReactorFsim did: added PMTs until a certain coverage is met.
My numerical work just now:
To calculate the area of coverage per PMT at a certain radius: pi * (r_pmt)^2 / (4 * pi * r_photocathode^2) = (20.16/2)^2 / (4 * (350-20)^2) = 0.00023325 = a. Yet a*1044 = 0.2435 and a*1160 = 0.27057. You can use the coverage per PMT at a radius for overall coverage.
On 16:41 Thu 27 Apr , Stan Seibert wrote:
> On Apr 27, 2006, at 4:11 PM, Matthew Worcester wrote:
>
> >Chris put the pmts in RAT, and I don't know exactly what formula he
> >used. There's a simple calculation in ReactorFsim to distribute
> >pmts evenly around a spherical detector. It is called SetPMT and
> >it lives in ReactorDetector.cpp. The code is attached below. The
> >baselines are: R2 is the approximate radius of the photocathodes,
> >PMTcoverage is 0.25 and PMTdiameter is 20.16 cm. The photocathodes
> >will be ~20 cm inside the steel vessel, and for a 350 cm outer
> >radius this gives 1044 pmts per detector.
>
> Chris copied a PMT location set from ReactorFsim, which I assume was
> generated with this formula, although we have 1160 PMTs in RAT, if I
> recall correctly.
>
> ---
> Stan Seibert
>
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