[Color_transp] [EXTERNAL] HGC

[Sebouh Paul]

Hi Dave and Bill,
Can you tell me more about this hole in the acceptance?  This sounds
concerning to me.
Thanks,
Sebouh

On Fri, Oct 31, 2025, 13:29 Dave Gaskell <gaskelld at jlab.org> wrote:
>
> Hi Sebouh -
>
> In principle, 0.65 atm should not be a problem - I think one would
> expect about 15 photoelectrons at that pressure.  However, there's a
> pretty big hole in the center of the acceptance that will need to be cut
> out.
>
> I'm cc-ing Bill Henry here as he takes care of the Cherenkov
> configuration for the Hall C experiments.  Bill - do you see any issue
> with running at 0.65 atm?
>
> Cheers,
> Dave
>
> On 10/31/25 12:35 PM, Sebouh Paul wrote:
> > Hi Dave,
> > We seek your advice regarding the HGC.  In the Pion CT experiment at
> > Hall C, we will want to detect pi+ and filter out kaons in the SHMS
> > using the HGC.  We calculated that in order to ensure that the index
> > of refraction is less than 1/β for the highest momentum kaons within
> > the acceptance in the SHMS at our highest momentum setting (the
> > central momentum would be approx 9 GeV, exact value TBD), we'd need to
> > have around 0.65 atm.  Would this be feasible?  Are there standard
> > procedures we would need to follow, or anything else we would need to
> > know, in order to set up the HGC for this experiment?
> > Thanks,
> > Sebouh
>