This is our photons target ! Injected with a 300mW Laser, the resonant cavity delivers more than 1kW of circularly polarized infra-red light ... Basics of resonant Fabry-Perot cavity for Compton polarimetry can be found in Nuclear Instruments And Methods In Physics Research Section A412 1 (1998) pp. 1-18. To reach and maintain a resonant state, one needs to ... turn the Laser On, and lock the cavity. In order to reduce systematic errors in the measurement of the electron beam polarization, the photon polarization can be reversed.

From time to time the cavity needs to be re-tuned. This requires to deal with the feedback system to lock the frequency of the Laser on a resonance frequency of the cavity, and the alignment of the laser beam with respect to the cavity optical axis. Here is the procedure for experts to do a cavity finess measurement.

Contact : F. Marie, Tel. 33-1-69082450.