Progress report on the A4 Compton backscattering polarimeter
The A4 collaboration at the Dept. of Nuclear Physics, University of Mainz, is conducting experiments on parity violation in the elastic electron-nucleon-scattering which require the use of polarized beams. In order to measure the absolute beam polarization, we have installed a Compton backscattering polarimeter in front of the target, using for the first time the internal cavity concept. A maximum intracavity intensity of 90 W has been measured, and in August 2003, first backscattered photons have been detected. This article describes the new design concept and the current status and results.