Spontaneous and stimulated γ radiation emitted by relativistic charged channeled particles (review)

An analysis is made of the current status of investigations of γ radiation emitted by channeled relativistic charged particles in single crystals. It is shown that the spectral and angular distributions of radiation emitted by channeled particles differ significantly from the corresponding distributions in the case of familiar coherent bremsstrahlung in crystals and they appear as a result of radiative transitions of a particle between different levels (bands) of the transverse motion. It is shown that by increasing the energy of the incident particle, it should be possible to obtain an emitted frequency in the x-ray and γ ranges as a result of the Doppler effect. Possible methods of amplifying γ radiation in a crystal are discussed. An analysis is made of stimulated radiation and the lasing threshold value of the particle current density is given.