[Halld-physics] current Ckov response in hdgeant

[Nathan Sparks]

Hi all,

Richard and I went over the problems I have been having with the Cerenkov simulation earlier. Here is a quick summary.

I had observed that the number of photoelectrons for Cerenkov hits is too small, but when he checked the simulation, he found a reasonable distribution for photoelectrons and also that the optics are working as expected (see previous email). We verified that I have the Cerenkov enabled in the geometry correctly and I use the same gustep.F. Then, I did the simulation using the same control.in file as Richard, but was still not able to reproduce the same results as Richard.  We realized that we were using different types of the code: He was using 32-bit code and I 64-bit. Next, Richard demonstrated that for the 64-bit code, the optics do not work correctly: light is not focused onto the PMT, and he is investigating further.

Regards,
Nathan

----- Original Message -----
From: Richard Jones <richard.t.jones at uconn.edu>
Date: Monday, April 11, 2011 4:41 pm
Subject: [Halld-physics] current Ckov response in hdgeant
To: "halld-physics at jlab.org" <halld-physics at jlab.org>

> Nathan and all,
> 
> I just re-enabled the gas Cerenkov currently defined (but disabled 
> by default) in the standard geometry and ran it, just to see if 
> something is broken.  To test it, I shoot 9 GeV pions at theta=8 
> degrees, phi = 0 degrees and count photoelectrons in the first 
> sector only.
> 
>     * pe statistics for first 100 events 
> <http://zeus.phys.uconn.edu/halld/hdgeant/ckov-4-
> 2011/ckov_pi_9GeV.gif>     * current settings: mirror reflectivity, 
> PMT window refractive index (for loss due to reflections at PMT 
> window), photocathode quantum efficiency 
> <http://zeus.phys.uconn.edu/halld/hdgeant/ckov-4-
> 2011/ckov_sim_params.gif>     * picture of geant tracking including 
> ckov photons bouncing off mirrors to PMT 
> <http://zeus.phys.uconn.edu/halld/hdgeant/ckov-4-2011/ckov_event.gif>
> 
> The Cerenkov radiation window is 1.5 - 5.0 eV.  This quantum 
> efficiency is not the best you could find for UV-sensitive 
> photocathodes.  Eugene's talk is also found in the same directory 
> as the links above.  It doesn't look like my QE curve corresponds 
> exactly to any of the ones shown by Eugene.  If you have a 
> preferred curve, I can put it in.
> 
> -Richard J.
> 
> 
>