Axial- to Planar-Channeling Transition

Axial and planar channeling of 1.0- to 2.8-MeV protons in silicon was studied both by transmission in some {μ}m-thick crystals and by Rutherford backscattering. Transmission experiments were simulated by a Monte Carlo program. A sharp transition between axial and planar channeling is observed by measuring both the effective stopping number B of channeled particles and the dechanneled fraction. Computer simulations exhibit the same features and show that at the transition, the transverse energy component is such as to produce a maximum probability of hitting the atoms. These experiments also give some criteria for the interpretation of backscattering measurements.