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Re: PS target issues (fwd)
Dear Hrachya,
Currently we have some space inside and outside the cave
as well (though the resolution is dominated by the beam
spot size at high energies, it's better to have only one
source with the dominant contribution).
For the rate/(PS background) studies the target position really
doesn't matter (I want to keep this position before I finish
with these estimates).
Cheers,
Sascha
On Thu, 11 Sep 2008, Hrachya.Hakobyan wrote:
> Dear Sasha,
>
> I'm sending this email with some delay due to my local over-occupancy
> yesterday.
> Thank you for calculations of MS influence. I ve already seen them
> and I ve sent slightly earlier my evaluation of MS effects to Richard (see
> below) and would remark on the distance of converter from Magnet. Richard
> has suggested the need in large distance, seems for direct polarimetry
> needs. At YeRPHI we applied even a 19m upstream setting. But for the
> ordinary PS functioning and aim to decrease the angular divergence
> influence, including that of MS , I suggest the use a converter insert at
> the entrance
> of the magnet, which corresponds to 3.5m long distance to FSF and WSF
> hodoscopes. For direct polarimetry needs the distance should be choosen
> big enough to provide a domonance of the pairs angular divergence over
> the beam spot size at the magnet entrance..
>
> Cheers, Hrachya
>
>
> ---------- Forwarded message ----------
> Date: Mon, 8 Sep 2008 17:35:34 +0500 (AMST)
> From: Hrachya.Hakobyan <hakopian@mail.yerphi.am>
> To: Richard Jones <richard.t.jones@uconn.edu>
> Cc: jstewart@jlab.org
> Subject: PS target issues
>
> Richard,
>
> You may easily check quantitatively that the influence of PS converter
> thikness,trough multiple scattering(projection angle's RMS) onto FSF and
> WSF arms is ranged from:
> - 0.2 to 0.62mm for thicknsses x=10^-3 10^-2 Xo and Ee=8GeV and distance
> 3.5m
> - 0.45 to1.15mm for thicknesses x=10^-3 to10^-2 Xo and Ee=3.5GeV
>
> Influens of mult.scat. is small and allows to increase the convererter
> thickness from 10^-3 to 5*10^-3 Xo, without worsening reslution. For end
> point energy measurement is also possible to use 1,2mm wide strips for
> better resolution,even thicker than 5*10^-3 Xo,while for CB peak
> measurements that is not allowed due to azimutal asymmetry of CB angular
> distribution. As a conclusion, there is a reserve for PS rate increse by
> use of thicker converter and end-point energy is possible to measure with
> better resolution, using 1-1.2mm wide strip and thickness up to 10^-2.
>
> Hrachya
>
>