RadPhi TechNote
radphi-2000-501
Optimum Target Thickness for Radphi
Richard T. Jones
University of Connecticut and Jefferson Lab
May 15, 2000
Abstract
The Radphi experiment uses a beryllium disk as a photoproduction target.
During 1999 commissioning we ran with a target thickness of 2.6cm and
found that the experiment could sustain rates up to
5•10
/s. For the main physics
run in Y2000 several additional target disks have been fabricated in
case we need them. Assuming that the requested radiator of
3•10
rad.len. is installed
we will have sufficient flexibility in terms of beam current to
consider either increasing or decreasing our target thickness, in steps
of 1.3cm. Increasing the target thickness diminishes our sensitivity
to detector backgrounds not associated with the target, eg. beam halo,
but eventually it begins to limit the angular resolution for showers
reconstructed in the lead glass. One also has to be concerned about
loss in efficiency due to conversions of final-state photons inside
the target. Decreasing our target thickness to 1.3cm can also be
considered if it would lead to a significant improvement in efficiency.
This note reports the results of a study of all of these effects, and
concludes that the target thickness of 2.6cm is close to optimum.
This page maintained by Richard Jones.