Microdosimetry of fast heavy ion beams

Biophysical and biochemical studies of the effects of high-LET radiation under way at numerous laboratories indicate the importance of understanding the pattern of energy deposition in volumes comparable to that of subcellular structures. The inadequacy of LET as a quantitative description of radiation quality has been shown in numerous experiments employing heavy charged particles. In order to better understand the molecular mechanisms responsible for the biological effects of high-LET radiation, it is important to obtain more detailed information regarding the stochastic nature of energy deposition in volumes of subcellular dimensions. During the past year we have completed a study of the distributions of ionization as a function of the radial distance from high-energy iron ions in collaboration with scientists from Lawrence Berkeley Laboratory (LBL) and Columbia University and initiated new studies at the UNILAC accelerator at GSI-Darmstadt, West Germany