ESR dosimetry in the ''gigarad'' range

ESR spectroscopy of radiation induced free radicals in organic and inorganic solids has recently been accepted for photon dosimetry in the high-level dose range. With alanine as the commonly used dosimetric material, the ESR spectroscopy has proven reliable applicability for doses up to 0.5 MGy irradiation and storage temperatures up to 500C. The upper detection limit is given by effects of saturation, respectively thermal instability of the radiation induced paramagnetic centres. For most solid materials saturation of the paramagnetic centres is reached at dose levels below or equal to 1 MGy. It was the subject of the present study to develop a dosimetric procedure that (a) allows for dosimetry at dose levels between, at least, 0.01 MGy and 0.1 GGy, (b) operates at irradiation temperature levels up to 2500C, and (c) is able to integrate the radiation dose over periods of up to 5 y. Among the different crystalline and amorphous materials investigated, crystalline quartz was found to match best the requirements. It is the E'1 centre in quartz that could be shown not to saturate up to absorbed doses of at least 50 MGy, and provide thermal stability up to at least 2000C for long periods of irradiation time. (author)