Beam Characteristics in the LANPF Biomedical Channel

We report on techniques to determine the muon component in the pion therapy beams at the Clinton P. Anderson Meson Physics Facility biomedical channel. The objective is to provide input to the project\´s treatment planning code PIPLAN which uses measured beam data to generate dose distributions. In these data it is important to identify the particles emanating from the channel by type, i.e., pion, muon, or electron. Muons from decays in the latter portion of the channel form a large "halo" around the pion beam. As our pion field sizes have increased, this "halo" has become an increasingly larger fraction of the beam. Results from beam measurements and computer simulations are presented.