The motion of energetic charged particles inside a monocrystalline solid can be strongly influenced by channeling and blocking effects. The present article reviews the theory, the experimental studies, and some of the applications of these effects. The coverage of the published literature extends through June 1973.

Channeling and related effects in the motion of charged particles through crystals

The production and use of a nuclear microprobe of ions at MeV energies

A method is described and demonstrated for a nondestructive determination of the hydrogen content inside materials in sheet form by measurement of the energy‐loss distribution from proton‐proton scattering events. The method is absolutely specific for hydrogen, and has a sensitivity of 1 ppm (atomic), or better. Materials analyzed (with ppm of hydrogen in parentheses) were: Ti (4200), Zr (5000), Al (20), Fe (∼ 10), C (13000), and Teflon (220). In the titanium and zirconium samples, the hydrogen content drops off near the surfaces. The method also detects oil or moisture on surfaces for thicknesses down to about 1 A; all materials studied had such surface films several hundred A thick.

Nondestructive Analysis for Trace Amounts of Hydrogen

Collimation of ion beams to micrometer dimensions

The qualitative features of the angular distribution of particles emergent from thin ∼ 1μ, uniform single crystals of silicon and germanium for incidence at small angles to axial directions are discussed in terms of the continuum picture of particle channeling. Blocking of axially channeled particles in the transverse plane is demonstrated. Implications and possibilities arising from observation of non-equilibrium of the transverse momentum vector are discussed. The use of the radial spreading of the angular distribution to investigate the average inter-atomic potential distribution in the plane transverse to the axial direction is explored and perturbations due to multiple scattering in surface films or inside the crystal and to beam divergence are qualitatively considered.

A qualitative description of the transverse motion of axial channeled particles in thin crystals

A technique for producing highly collimated beams of negative ions using apertures is discussed. The application of the method produced a 30 μ diam H− beam with an angular divergence of 1.5 mdeg. The results of a study of the small angle scattering of protons from a carbon are presented. Other possible applications are outlined.

H. E. Wegner

Papers

Supercollimation of Negative Ion Beams with Apertures