Dechannelling of fast ions at dislocations

The probability of a channelled ion being knocked into a random trajectory as a result of lattice distortion near a dislocation is investigated using computer simulation to generate directly the trajectories of channelled ions. The width over which dechannelling can occur on either side of the dislocation is given with good accuracy by an analytic formula due to Quéré [2]. However the probability of a dechannelling event per individual channel within this region is normally much less than unity. The total dechannelling, proportioned to the probability and the width, is considerably smaller than predicted by Quéré. The total dechannelling (i) varies as b3/2, where b is the Burgers vector of the dislocation; (ii) is independent of energy at low energies; and (iii) varies as E1/2 at high energies.