EXPERIMENTAL FINDINGS IN 180-DEGREES BACKSCATTERING ENHANCEMENT FROM SOLIDS

We use a backscattering assembly developed recently to investigate the enhanced backscattering from polycrystalline materials near 180 degre es. The nominal scattering angle can be continuously varied between ex actly 180.0 degrees and 178.5 degrees. It is shown that the stochastic model of flux peaking, though its predictions are surprisingly consis tent with experimental results, either does not apply to real measurem ents or does only take account of a negligible fraction of the effect, which cannot be documented by experiment. The energy loss of He proje ctiles along correlated inward and outward trajectories turns out to b e the same as in any random direction. To get the enhancement factor u naffected from detector resolution we measured the integrated backscat tering yield from a number of targets with different thickness and ded uced the yield by two different methods. For 400 keV He projectiles sc attered from partly oxidized Ta a maximum enhancement factor of 2.8 is found.