Radiation Quality of Californium-252

The radiation quality of 252 Cf has been determined in a tissue-equivalent phantom for simulated sample sizes of 1 and 2 μm. The measurements were made with a 2.54 cm spherical proportional counter of tissue-equivalent plastic with a source-to-counter distance of 7.8 cm. Event spectra have been obtained for lineal energy densities between 0.04 and 10 3 keV μm -1 . The distributions in both lineal energy density and LET are presented. The dose mean of the distribution in lineal energy density is 38 keV μm -1 for the 1 μm site and 34 keV μm -1 for the 2 μm site. Correspondingly, the dose mean values of the distribution in LET are 34 and 30 keV μm -1 respectively. A mean quality factor of about six for 252 Cf is obtained for the geometry used here. The absorbed dose rate per unit source mass was found to be 11 rad s -1 g -1 , in substantial agreement with most previous measurements, and the ratio of absorbed dose due to protons and other heavy particles to that of electrons is approximately 0.9.