Dependence of the images of the imaging plate on incident angles of heavy nuclides

We are investigating the basic characteristics of an imaging plate (IF) as a detector for ultra-heavy cosmic rays. Irradiating the IPs with Ar and Fe particles from several incident angles, the images on the IP were measured. We confirmed that the images due to particles extend to the incident direction and that the information is useful for the determination of the incident angle. Moreover, we found a certain relation between the incident angle and the photostimulated luminescence (PSL) value on the IP due to the deposited energy. Using the relation, we can find out the PSL value at which the particle would be injected perpendicular to the IF. From the normalized PSL value, the dE/dx of the particle can be determined. As the relation is held independently of the nuclide and the energy of the incident particle, it is useful to measure the dE/dx