Influence of the Irradiation Temperature on the Free-radical Response of Alanine.

GSF operates the only IAEA high-level dosimetry reference laboratory and, as a joint project with the IAEA, the International Dose Assurance Service (IDAS). Dosimetry is based on long-lived free radicals in organic alanine induced by ionizing radiation and readout by ESR spectroscopy. The thermal time response of the radical concentration in alanine is fairly constant after irradiation provided that the alanine samples are stored at temperatures below 50°C. By contrast, a positive temperature coefficient had earlier been found at GSF for the production rate of alanine radicals, for irradiation temperatures between 0 and 50°C. This effect has to be considered for reference dosimetry in radiation processing. Radiation processing is also of interest at irradiation temperatures below 0°C. The present study describes experiments on the influence of irradiation temperatures between +50 and -100°C. Comparison is made between the present and earlier results, in the overlapping temperature range. An empirical function is proposed for the temperature coefficient based on the experimental data