Observation of Fine Structure in Channeling of Particles in Bent Crystals.

We observed highly efficient manipulation of the 530 MeV positron beam at Mainz Microtron via bent crystals. The low beam divergence revealed a fine structure in the angular distribution of channeled particles. A compact analytical model, supported by Monte Carlo methods including multiple scattering, accounts for the measurements. We established a criterion for designing a crystal with reduced angular spread of channeled particles for beam manipulation at any energy. This finding is particularly useful in view of applications of channeling to the highest energies.