Calibration experiments of CR-39 with 16O, 20Ne and 40Ar ions of more than 100 MeV/u at HIMAC

A calibration experiment of CR-39 with Ar ions for space heavy ion identification has been performed. It is necessary for studying mechanism of mutation breeding induced by space particles. In the experiment, 40Ar ion beams with nominal energy of 500 MeV/u and density of 500 cm-2 supplied by HIMAC were used to irradiate a stack of 18 pieces of CR-39 films vertically. After degraded by a binary filter, the energy at sample position was about 100MeV/u. After the films were etched (etch time t), diameters (d) of the tracks in respective films along a trajectory were measured under a microscope. Then, etch rates VT (=d/2t) were got. Relative distances (R) to every VT refer to the stack bottom (usually film 1 of ion incidence as reference). A fitted line and its fitted formula could be drawn from R in ordinate and VT-1 in abscissa. The slope (dR/dVT-1) of the line was obtained. It is just the point in the calibration curve we need. (author)