Channeling, superfocusing, and nuclear reactions

Abstract

A highly collimated beam of protons (≈1 MeV) entering the channel of a monocrystal film forms at a certain depth an extremely sharp (<0.005 nm) and relatively long (some monolayers of the crystal) focusing area where the increase of the flux density can reach hundreds times. Impinging atoms in this focusing area can undergo nuclear or atomic reactions with proper foreign dopants which disappear if the crystal is tilted from this position by only 10−3 rad. This effect can be called channeling superfocusing, in contrast to the ordinary flux peaking where the increase of flux density reaches only few times. Results are predicted by the exactly solvable quantum mechanical model calculations and confirmed by channeling Monte Carlo simulations accounting for several properties of the real lattice. Unfortunately, the mosaic structure of the film and statistical spread of the film and statistical spread of the axes of channels prevent the observation. Special technologies and materials choice are needed to minimize this effect.