| Compton T. Pussieux The Hall A Compton Polarimeter In order to measure the longitudinal polarization of the 3-6 GeV high intensity TJNAF electron beam, a Compton Polarimeter was built by Saclay Clermont , and Jlab . The Compton was used for the HAPPEX parity violation experiment in 1999 and for the N-Delta experiment in 2000. The Compton effect, light scattering off electrons, discovered by Arthur Holly Compton (1892-1962), Nobel prize in Physics, 1927 , is one of the cornerstone of the wave-particle duality. Compton scattering is a basic process of Quantum Electro-Dynamic, the theory of electromagnetic (EM) interactions. This is a well established theory, and is thus natural to use the EM interaction, such as Compton scattering, to measure experimental quantities, such as polarization of an electron beam. Many of the Hall A experiments of Jefferson Laboratory using a polarized electrons beam require a measurement of this polarisation as fast and accurate as possible. Unfortunately the standard polarimeters, like , require the installation of a target in the beam. Therefore, the polarisation measurement can not to be performed at the same time than the data taking because the beam, after the interaction with the target, is misdefined in terms of polarization, momentum and position. Another physical solution has to be found in order to permit a non-invasive polarisation measurement of the beam. This is the principle of the Compton Polarimetry. | |
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