We describe a direct method for monitoring the geometrical dimensions of a
synchrotron beam at the target position for internal target installations.
The method allows for the observation of the proton beam size as well as th
e position of the beam relative to the target. As a first demonstration of
the technique, we present results obtained by means of the COSY-11 detectio
n system installed at the cooler synchrotron COSY. The influence of the sto
chastic cooling on the COSY proton beam dimensions is also investigated. (C
) 2001 Elsevier Science B.V. All rights reserved.