High-energy beam transport in crystal channels

The transport of high-energy accelerating charged particles in channeling conditions in a crystalline solid is considered by means of a Fokker-Planck model. Multiple scattering on electrons, appropriate to the channeling of positive particles, and radiation damping due to the emission of channeling radiation are also included. Analytic solutions have been obtained for the case of a harmonic channeling potential. Without acceleration, diffusion due to multiple scattering occurs. With acceleration, the adiabatic damping retards this, although the reduction in critical channeling angle with increasing energy eventually competes. For light particles (positrons), the emission of channeling radiation can lead to a steady state. Implications for crystal accelerator schemes are discussed.