Eur. Phys. J. A 24, s2.129-s2.130 (2005)
DOI: 10.1140/epjad/s2005-04-030-2

The transmission Compton polarimeter of the A4 experiment

Christoph Weinrich

Johannes-Gutenberg-Universtität, Institut für Kernphysik, J.-J.-Becher-Weg 45, 55099 Mainz, Germany

(Received 01 November 2004 / Published online 08 February 2005)

Abstract

A transmission Compton polarimeter as a simultaneous, relative monitor for the longitudinal polarisation of a stabilised, polarised electron beam (polarisation degree ~ 80 %) has been constructed in a new design. It is located in the vacuum between the target and the beam dump of the A4 parity violation experiment at MAMI. The analysing power is ~ 80 ppm at 854 MeV and ~ 115 ppm at 570 MeV. The measurement precision for the polarimeter asymmetry (which is proportional to the longitudinal beam polarisation degree) is ~ 3 ppm within 5 min. at 854 MeV and ~ 7 ppm within 5 min. at 570 MeV and the systematical error is about 0.5 ppm + 1 - 2 %. This simple polarimeter consists mainly of two graphite scatterers, a water-cooled Samarium-Cobalt permanent magnet, an aluminum secondary electron emission monitor, an understructure and electronics.

PACS: 29.27.Hj Polarized beams - 29.27.Fh Beam characteristics

The Author, for the A4 Collaboration. This work comprises part of the author's PhD thesis.

© Società Italiana di Fisica, Springer-Verlag 2005