\documentstyle[11pt,apsab]{article}
\nofiles
\MeetingID{DNP08}
%\DateSubmitted{20080701}
%\LogNumber{DNP08-2008-000477}
\SubmittingMemberSurname{Jones}
\SubmittingMemberGivenName{Richard 
}
%\SubmittingMemberID{60028219,USA}
\SubmittingMemberEmail{richard.t.jones@uconn.edu}
\SubmittingMemberAffil{University 
of Connecticut}
\PresentationType{poster}
\SortCategory{12.}{}{}{}
\received{01 
Jul 2008}
\begin{document}
\Title{Beam Position Stabilization Using an Active 
Collimator in Hall D at Jefferson Lab}
\AuthorSurname{Jones}
\AuthorGivenName{Richard 
}
%\AuthorEmail{richard.t.jones@uconn.edu}
\AuthorSurname{Senderovich}
\AuthorGivenName{Igor}
%\AuthorEmail{senderovich@phys.uconn.edu}
\AuthorAffil{University 
of 
Connecticut}
\AuthorSurname{Collaboration}
\AuthorGivenName{GlueX}
\thanks{photon 
beam working group}
\CategoryType{E}
\begin{abstract}
The GlueX experiment 
planned for Hall D at Jefferson Lab relies
on the process of coherent bremsstrahlung by 12 GeV electrons in
a diamond crystal to produce a secondary beam of 9 GeV photons
with a high degree of linear polarization.  To achieve optimum
polarization, the photon beam must be collimated to a half-angle
of 20 $\mu$r, which requires a long flight path of 75 m
between the radiator and collimator and a means to keep the beam
spot centered on the collimator aperture with an accuracy of a
few $\mu$r.  A active collimator has been designed which is
capable of monitoring the centroid of the photon beam to within
$\pm 200$ $\mu$m, with a sampling frequency of up to several
hundred Hz.  A prototype of this this device has been tested in
the photon beam in Hall B.  Results from this test are 
presented.
\end{abstract}
\end{document}

