Ionization in Microscopic Volumes Irradiated by Energetic Photons.
OREGON STATE UNIV CORVALLIS RADIATION CENTER
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The energy absorbed by microscopic volumes exposed to ionizing radiation is not well represented by the average dose due to the small number of discrete energy transfers involved. The energy deposited in a microscopic volume can be determined by measuring the ionization in a detector filled with gas at low pressure. A grid-walled spherical proportional counter suitable for making such measurements for photon irradiation is described and compared to a solid-walled counter. Measured ionization distributions are presented for 60Co gamma irradiation, filtered and unfiltered 250 kVp x-rays, and for 65 kVp x-rays. Other distributions which may be of use in understanding radiation damage models are calculated from these measured distributions. Author