Gyromagnetic autoresonance: Phase stability in a photon factory regime

The theory of ultrarelativistic gyromagnetic autoresonance is developed with emphasis on destabilizing effect of synchrotron radiation on the particle dynamics. A special regime in which the acceleration, due to the rotating electric field, is nearly or totally compensated by deceleration, due to the radiative braking (Photon Factory Regime) is investigated. The main results are: (1) the Photon Factory Regime is unstable when acceleration and radiative retardation are strictly compensating each other, (2) the phase stability is restored if the magnetic field is maintained at a level slightly lower than that in the case of exact compensation. © 1984 IOP publishing Ltd.