The photons resulting from the interaction of beta particles and matter have a certain complexity of origin; but the spectrum is made up, in large part, of two primary components, one of these being the white radiation continuum produced by the external bremsstrahlung mechanism of beta acceleration at the target atom. The second fraction consists of the characteristic K and L X-rays of the target atom. Published beta-excited X-ray spectra are centered about a small fraction of the available pure beta emitters and a restricted group of target materials. Furthermore, intercomparisons between references are difficult, due to an infinite variety of source and detector parameters influencing the data.
This laboratory has begun a comprehensive reference compilation of these spectra, done on a comparative basis and simplified and standardized for sensible cataloging and easy reproduction of the experimental design. The prime purpose is to make available coherent data for many beta-excited X-ray sources in which beta activities, target geometries, and other critical parameters are known, controlled, and constant. Spectral sets for given source-target combinations may, therefore, be intercompared, and application of the beta-excited X-ray may be made with the best possible source-target atom combination.
The spectra are studied by three proportional counters (operating down to the 1 kV energy range) and two standard scintillation crystals, accumulated in a 256-channel analyzer, and are presented in sets (representing one beta source-target combination) consisting of a minimum of eight spectra, six of which represent the most critical transmission target geometry.
Examples of the cataloging of the spectral sets, for the mixture, apposition, and compound isotopic X-ray sources, are presented.