When a beam of charged particles enters a single crystal along a major crystallographic planar or axial direction, one observes a spectacular reduction of the yield associated to events that imply close nuclear encounters (nuclear reaction, large angle elastic scattering, formation of core-shell electron vacancies on target atoms and corresponding X-ray emission. . .). All these effects are characteristic of a phenomenon called Channeling, discovered and explained 40 years ago [1]. Channeling is the direct consequence of the fact that, in the particular beam-crystal geometry described above, the particles experience strongly correlated binary collisions with target atoms. These collisions focus the beam far from the atomic strings or planes of the crystal. Thus, the uniform flux associated to an beam impinging a crystal surface becomes progressively highly non-uniform as the particles penetrate in the bulk, with a pronounced maximum at the center of the ‘channels’ delimited by the atomic rows or planes.

The effect of channeling/blocking is studied with Medipix type semiconductor pixel detectors.