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

[A.M. Sandorfi]

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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