Microdosimetry of negative poins at LAMPF.

Lineal energy distributions and linear energy transfer (LET) spectra are being measured at the biomedical facility of the Los Alamos Scientific Laboratory for a negative pion beam having an initial momentum of 168 MeV/c. The results show that the fraction of the dose for lineal energies greater than 50 keV/mum is approximately 2% in the plateau and approximately 12% at the Bragg peak. Preliminary data indicate that the high lineal energy (and high LET) component increases significantly in the region slightly downstream from the peak.