Experimental Determination of the Low-Energy Spectral Component of Cobalt-60 Sources

摘要

A knowledge of the relative fraction of low-energy photons in the energy spectrum of cobalt 60 irradiators is essential to the proper interpretation of dosimetry and device test data in radiation response testing of electronic devices and circuits. It is shown that the relative magnitude of the low-energy spectral component of cobalt 60 gamma radiation can be determined experimentally by the use of a gold-and aluminum-walled air ionization chamber. The design and details of the construction of such a chamber are given. Experimental data from a large variety of cobalt 60 irradiator facilities are given and the facilities are ranked in order of the gamma spectrum hardness. Finally it is shown that the ionization chamber data can be used to calculate an upper limit on the expected interface dose-enhancement factor for a given material geometry. Keywords: Dose enhancement; Cobalt 60 irradiator; Radiation hardness testing; Photon spectrum; Differential absorption spectrometer; Ionization chamber; and Interface dose enhancement.