The minimum yield in channeling

A first estimate of the minimum yield was obtained from Lindhard's theory, with the assumption of a statistical equilibrium in the transverse phase-sp ace of channeled particles guided by a continuum axial potential. However, computer simulations have shown that this estimate should be corrected by a fairly large factor, C (approximately equal to 2,5), called the Barrett fa ctor. We have shown earlier that the concept of a statistical equilibrium c an be applied to understand this result, with the introduction of a constra int in phase-space due to planar channeling of axially channeled particles. Here we present an extended test of these ideas on the basis of computer s imulation of the trajectories of 2 MeV alpha particles in (1 0 0) Si. In pa rticular, the gradual trend towards a full statistical equilibrium is studi ed. We also discuss the introduction of this modification of standard chann eling theory into descriptions of the multiple scattering of channeled part icles (dechanneling) by a master equation and show that the calculated mini mum yields are in very good agreement with the results of a full computer s imulation. (C) 2000 Elsevier Science B.V, All rights reserved.