Re: Tagger energy resolution? (fwd from David)

[Alexander Somov <somov@jlab.org>]

Hi David,

> Thanks Sascha for the correction on the microscope range. I will include the 
> correct range
> in my talk. I'm not getting something about what the 2% of 12GeV (=240MeV) 
> represents.
> Is this the actual tagged photon resolution? If so, what happened to the 
> 60MeV?

Sorry, it was a misprint, I meant 0.02% of course. The beam optics 
resolution is ~2.4 MeV.

> I'm not sure though that I follow the fixed array argument. It would seem 
> that
> the limitation of the electronics would be applied on a per channel basis. If 
> the single
> channel rate is 5MHz, then that would be a hit once every 200ns which the 
> scintillator
> and our electronics should easily handle. Is the 20 counters coming from the 
> solid angle
> subtended by a bundle of 20 fiber scintillators into the magnet being about 
> the same as
> that of a single fixed array scintillator? I guess that would make sense (5 
> scintillators per
> energy bin times 4 (8MeV) energy bins would cover 32 ~= 30MeV). However, I'm 
> not
> sure how well the argument holds even then since more than half of the rate 
> is contained
> in the center fiber of a row of 5 in the microscope (see slide 6 of Igor's 
> talk GlueX-doc-1167).

I was talking about accidential in the fixed array in the range above 
9.0 GeV (if you want to tag with the fixed-array counters in the range 
9-11.7 GeV). There are 90 fixed-array counters in this range, each 
counter's rate is roughly 5MHz. The total rate is ~450 MHz (at high lumi).
(the probability of double hits in a 2 ns window is 90%)

Cheers,
        Sascha