Calculation of Muon Depth Distributions in Thin Film Single Crystals

To investigate the effects of sample crystallinity and the consequent channeling on the stopping distribution of low energy muons, we compare the results of the well-known binary-collision-approximation code(BCA): TRIM to results from MARLOWE from Oak Ridge National Laboratory, and those of a code which we have written and given the acronym MUSCLE. TRIM assumes an amorphous stopping medium. MARLOWE is also a BCA code, but treats the stopping medium as crystalline. MUSCLE uses a molecular dynamics approach and should be even more accurate. For the results shown here we use bcc Fe. TRIM, MARLOWE, and MUSCLE are Monte-Carlo codes. We find that the average penetration depths are similar, but that the detailed shapes of the penetration distributions are quite different. When the dependence of the interpretation of experiments depends on the relative probabilities of penetration depth, a use of code which includes the effects of crystallinity is recommended.