CERN Accelerating science

Preprint
Report number	EXT-2004-056 ; IPNO-DR-2004-06
Title	First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO
Author(s)	Collin, B ; Arianer, J ; Essabaa, S ; Frascaria, R ; Gacougnolle, R ; Kunne, Ronald Alexander ; Aulenbacher, K ; Tioukine, V
Affiliation	(IPN, Universite Paris 11,Orsay, France) ; (Institut fuer Kernphysik,Johannes Gutenberg-Universitaet Mainz, Germany)
Publication	2004
Imprint	11 Jun 2004
Number of pages	17
Subject category	Accelerators and Storage Rings
Abstract	The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5 nm which is observed and analyzed.
Submitted by	[email protected]