Radiological physics and dosimetry research with a small positive ion accelerator

The distribution of energy along and around the path of charged particles is the fundamental determinant of the chemical and biological effects of ionizing radiation. The current status for measuring the energy deposition in simulated biological matter is reviewed. Inasmuch as current radiobiological information indicates that the sensitive volume is very small, diameter of order one micrometer or smaller, deposition in volumes of this dimension are of primary interest. Limitations of experimental techniques make the direct measurement of energy deposition in such small volumes difficult and hence very uncertain. A Monte Carlo method for calculating this discreet initial track structure is discussed. The input data for calculations of microscopic energy depositions are double differential cross sections for electron ejection by energetic ions. The current status of the experimental measurement of these cross sections is reviewed.