Darmstadt 2008 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 25: Instrumentation und Anwendungen I

HK 25.3: Talk

Tuesday, March 11, 2008, 11:45–12:00, 2C

The Compton polarimeter at the electron stretcher accelerator ELSA — •Jürgen Wittschen — Electron Stretcher Accelerator ELSA, Physikalisches Institut, Universität Bonn, Germany

Part of the hadron physics program performed at ELSA in the framework of the SFB/TR16 focuses on double polarization experiments, where both the beam and the target are polarized. In order to supply an external beam of high polarization a large number of depolarizing resonances have to be successfully compensated. It is therefore mandatory to determine the beam polarization. This measurement is based on Compton backscattering of circularly polarized laserlight off the electron beam. The polarization degree is extracted from the shift of the center of the photon spatial distribution when switching the polarization of the laserlight from left to right handed polarization. Precision polarimetry requires a measurement of the shift with an accuracy of a few microns. In order to reach this accuracy, a counting silicon microstrip detectorsystem has been developed and set up.

In the talk the status and expected performance of the polarimeter will be presented.