[Halld-pid] TOF PMT selection and scintillator selection

[Mark M. Ito]

Paul,

That makes sense.

If testing _all_ of the scintillators first is a practical issue, one 
could imagine schemes where they are tested in batches and sorted into 
classes that would allow assigning tubes before every single 
scintillator is tested. Less than optimal, but probably not by much. A 
side effect would be that production could not possibly follow 
installation-on-frame order.

And if it is not and issue, it is not an issue.

   -- Mark

On 04/26/2013 09:21 AM, eugenio at fsu.edu wrote:
> Hi,
>
> Recall at yesterday's meeting we discussed how we planned to match PMT pairs for gluing onto modules.  The plan was to match those with similar gain but different noise characteristics(i.e. noisy with quiet).   We also mentioned that we planned to have high gain tubes used on modules near the center beam hole.  That way, as gain deteriorates  due to dynode ablation, we can increase the gain on these tubes.
>
> Sasha and I continued this discussion after the meeting yesterday, and we think that the scintillator attenuation lengths should also be considered in matching PMT pairs to modules.   The measured attenuation lengths vary from 250 cm to 400cm.  We would like to select those with the highest values for modules near the center.   The modules near the outer edge can have lower values as hits in the outer modules are confined to the paddle center and therefore light would only travel half a paddle length.
>
> For us to proceed in this manner, we would have to measure all scintillators before attaching PMTs.
>
>
> --
> Prof. Paul Eugenio
> Florida State University
> Department of Physics
> Tallahassee, Florida,  USA 32306
>
> (850) 325-0314
> eugenio at fsu.edu
>
>
>
>
>
>
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-- 
Mark M. Ito, Jefferson Lab, marki at jlab.org, (757)269-5295