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Summary
In principle, resonant cavities can be excited by magnetic moments of a polarized beam, thus allowing to determine the beam’s polarization by measuring the amplitude of the resonating cavity’s fields. The steady state field amplitude can be determined by calculating the energy transfer from the beam to the resonator’s fields. Analytic formulas for different cavity modes are obtained by integrating over the longitudinal relativistic Stern-Gerlach force. It is shown that in case of ultra-relativistic electrons the signal for transverse polarization is independent of beam energy whereas the signal for longitudinal polarization scales with 1/gamma. The expected signal power is derived for different cavity modes and compared with thermal noise and background by cavity excitation due to charge interaction. A possible layout for first prove-of-principle experiments at CEBAF/JLAB and ELSA/Bonn is presented and a possible employment at future storage rings is illustrated.
