Concerning one feature of energy conversion in diffraction-radiation generator/free-electron laser systems

A novel excitation mechanism has been observed in diffraction-radiation generator/free-electron laser systems which leads to the generation of self-oscillations under conditions when the initial electron velocity is less than the phase velocity of the synchronous component of the open-cavity field. Here, it is shown that this mechanism involves nonlinear transfer of electron energy to the open-cavity field. The features observed in the tuning of diffraction-radiation generator/free-electron laser systems using the beam current and accelerating voltage in the case when the phase velocity of the synchronous component of the open-cavity field exceeds the initial electron velocity are examined with reference to both theoretical and experimental results.