SCATTERING OF FAST PROTONS INCIDENT AT GRAZING ANGLES ON THE SURFACE OF A SINGLE CRYSTAL. GUIDING OF CHARGED PARTICLE BEAMS BY CRYSTALS.

Computer simulation is used to study the reflection of 10 Mev protons from the (100) and (110) planes of a tungsten crystal when the beam is incident at grazing angles and channeled in a plane. The angular spread of the reflected beam due to multiple proton scattering by the nuclei in the crystal increases as the crystal is heated and as the angle THETA //0 between the incident beam and the face to the crystal increases; the angular spread also increases if the plane of incidence of the beam contains approximately with an axis of densest packing on the surface of the crystal. Even for THETA //0 equals THETA //c, where THETA //c, is the critical angle for plane channeling, the halfwidth of the angular distribution of the reflected protons is DELTA THETA // one-half approximately equals 0. 01 THETA //0 at room temperature; this is approximately 10**2 less than when protons are reflected by an equivalent amorphous target under the same conditions. The results indicate that multiple reflection of a beam by a system of crystals can be achieved under conditions of planar channeling, i. e. , that crystal can be used as ionguides.