Radiation suppression and its oscillatory dependence on target thickness at passing of fast charged particles through an ultrathin crystal

Abstract

We consider the possibility of observation of the coherent radiation suppression effect occurring at motion of GeV positrons in the field of (110) crystal atomic planes of thin Si crystals, and its oscillatory dependence on crystal thickness. The particles move in the regimes of channeling or above-barrier motion when crystal thickness is smaller than the radiation formation length, and the particle performs not more than a few full oscillations. The dependences of the spectral radiation density on crystal thickness, particle energy and particle incidence angle are obtained. We indicate how the peculiarities of the behavior of the spectral density of radiation come from those of the scattering process. The influence of angular divergence of the beam on the studied effect is considered. It is shown that there exist conditions under which at least the suppression effect, if not the oscillatory one, can be observed experimentally. For example, these can be reached within the collaboration CERN NA63.