Alanine radicals, part 4: relative amounts of radical species in alanine dosimeters after exposure to 6-19 MeV electrons and 10 kV-15 MV photons.

The amino acid l-alpha-alanine can be used for high-precision dosimetry over a wide dose range, using EPR spectroscopy for monitoring radical concentrations. It is important, however, to understand the underlying composition of the observed EPR spectrum. In previous work, it was shown that the EPR signal from irradiated alanine consists of at least three different radical species, with the relative importance of each of these being almost independent of absorbed dose. However, it was not known whether the relative importance of each radical is independent of the radiation quality responsible for the EPR signal. In the present work, the relative contributions of the different radical species to the total EPR signal from alanine dosimeters irradiated with 6-19 MeV electrons and 10 kV-15 MV photons at a dose of 10 Gy were examined. By spectrum reconstruction using benchmark spectra generated from a simulation procedure, the relative amounts of the three different radical species were shown to be virtually independent of these radiation beam qualities.