ESR DOSIMETRY WITH MAGNESIUM-SULFATE

The aim of the investigation is to enhance the ESR dosemeter sensitivi ty in the therapy dose range below 10 Gy, where the ESR spectrum of th e alpha-alanine radical becomes increasingly difficult to evaluate for dosimetry. Anhydrous magnesium sulphate, MgSO4, appears to be an exce llent candidate from the spectrometric point of view. On irradiation w ith Co-60 gamma-rays the stable radical SO3-is produced whose ESR sign al amplitude increases linearly with dose up to about 10(5) Gy. Ignori ng the abundant isotopes O-17 (0.04%) and S-33 (0.74%), the spectrum o f SO3- is a single line at g = 2.0036 of width 0.5 mT which is stable at temperatures up to at least 120-degrees-C. Using the conventional p eak-to-peak method of dosemeter readout, the MgSO4 dosemeter is somewh at more sensitive than the traditional alanine dosemeter of the same m ass. Its main advantage over the alanine dosemeter is, however, the ea se of computer enhancement and the possibility of integration which th e single-line spectrum offers.