Radiation of channelled positrons and electrons; possibilities of application

When a beam of charged particles traverses a crystal along closely packed atomic strings or planes, the particles undergo correlated collisions with the atoms which leads to a constrained motion that is termed channelling. In 1976, M.A. Kumakhov, predicted that channelled positrons or electrons of relativistic energies would radiate, and that as the electric field created by atomic strings or planes is of the order of 1010-1011 V/cm, the radiation should be intense. While the characteristic frequencies of particle trajectory oscillations in channels is 1015-1016/s, the radiation frequencies, owing to the Doppler effect, are shifted to the X and γ-ray region. The author reviews the theoretical aspects and experimental results. (Auth.)