Physical characteristics of 670A MeV /sup 20/Ne at its Bragg peak

The dose delivered to a patient in heavy ion radiotherapy is dependent not only on the properties of the primary beam, but also on the properties of its secondary fragment distribution. Measurements are presented for several points on the unmodified Bragg peak of 670 A MeV /sup 20/Ne giving the charge and velocity distributions of the beam components. The experiments were performed at LBL's Bevalac Bio-Medical Facility using a time-of-flight particle identification spectrometer. The authors will present for a high statistics run the derived LET spectra for each fragment. Once corrections for backgrounds and acceptance have been made to the data, then the experimental measurements of the fluence, charge, and velocity of beam components constitutes a complete characterization of this point on the Bragg curve. The interpretation of radiobiological experiments at this point can then be made in terms of models of the direct biological action of radiation rather than in the more primitive terms of averaged quantities