Irradiations with the track segment facility and the analysis of data

Results from track segment irradiations of synchronized mammalian cells are reported previously for a range of LET values listed with the ions used and their LET values. The highest LET values resulted from helium track segments with a considerable change in LET across cellular dimensions. The survival curves obtained for two phases of the cell cycle, namely G1/S and late-S, were fitted by computer analysis to the form: S = e/sup -αD-βD2 where D is the dose and α and β are constants. The best-fit values of the parameters, α and β, are tabulated with 95% confidence limits indicated for protons, deuterons and helium -3 ions. The LET trends of the survival curve parameters for late-S and G1/S cells, respectively, are indicated