[G14_run] Natalie's talk at 10-12-12 meeting - collimators

[Eugene Pasyuk]

Andy, 

Having 25 mm target would have increased energy losses in it and therefore the threshold, particularly for protons.

-Eugene

----- Original Message -----
> From: "A.M. Sandorfi" <sandorfi at jlab.org>
> To: "Eugene Pasyuk" <pasyuk at jlab.org>, "Reinhard Schumacher" <schumacher at cmu.edu>
> Cc: "g14 run" <g14_run at jlab.org>
> Sent: Wednesday, October 17, 2012 1:06:09 PM
> Subject: Re: [G14_run] Natalie's talk at 10-12-12 meeting - collimators
> 
> Folks,
> As Eugene mentioned, Linear polarization from diamond required a 2.0
> mm
> collimator to define angles and maximize the photon polarization.
> This
> produced a spot of about 7.5 mm OD on target and our cell was 15 mm
> ID.
> 
> For circular running we just copied the g9 conditions and used the
> 2.6 mm
> collimator. But we could easily have made 25 mm ID targets so, while
> it's
> unpleasant to think of these things now, I guess for circular running
> in g14
> we could have used a larger collimator, which would have given us
> more flux
> on target - sigh!
> 
> Andy
> 
> 
> 
> 
> On 10/17/12 12:57 PM, "Eugene Pasyuk" <pasyuk at jlab.org> wrote:
> 
> > Reinhard,
> > 
> > This is because for g14 run we collimated (2.6 mm for circularly
> > polarized and
> > 2mm for linearly polarized) photon beam while for g1c and g11 the
> > beam was
> > uncollimated.
> > We used small collimator to make sure the beam does not hit target
> > cell walls.
> > The inner diameter of the HD cell is 15 mm. With this collimation
> > beam spot
> > size on target is bout 10 mm. The targets for g1c and and g11 had
> > diameter 60
> > and 40 mm respectively.
> > 
> > -Eugene
> > 
> > ----- Original Message -----
> >> From: "Reinhard Schumacher" <schumacher at cmu.edu>
> >> To: "g14 run" <g14_run at jlab.org>
> >> Sent: Wednesday, October 17, 2012 12:47:17 PM
> >> Subject: [G14_run] Natalie's talk at 10-12-12 meeting
> >> 
> >> Hi Natalie,
> >> I liked looking through the slides of your talk last Friday, the
> >> one
> >> at
> >> the Collaboration meeting I missed.  There is some interesting new
> >> material.
> >> 
> >> My immediate question is about slide 13 showing a measurement of
> >> the
> >> beam line transmission function, based, I assume, on an analysis
> >> of
> >> the
> >> TAC data from a normalization run.  Why is the transmission
> >> efficiency
> >> as small as 35%?  For g1c and g11 the transmission fraction was
> >> much
> >> larger.  Is it because of the size of the collimator?  If that is
> >> the
> >> case, why did we use such a small collimator?
> >> 
> >> Anyone can comment on this of course, not just Natalie.
> >> 
> >> Cheers,
> >> Reinhard
> >> 
> >> 
> >> --
> >> ___________________________________________________________________
> >> Reinhard Schumacher         Department of Physics, 5000 Forbes
> >> Ave.
> >> Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.
> >> phone: 412-268-5177         web: www-meg.phys.cmu.edu/~schumach
> >> ___________________________________________________________________
> >> _______________________________________________
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> >> 
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> 
>