Interlaboratory beta source calibration using TL and OSL on natural quartz

Laboratories using luminescence methods for dose reconstruction have to make interlaboratory source calibrations-initially this will be a single isotope beta or gamma source using one particular reference material. The procedure requires not only the administration of exact doses to the material but also the uniform handling of the dosimetric material and standardization of the procedures.

An interlaboratory calibration of an Sr-90 beta source was recently carried out by our five laboratories which are involved in a retrospective project. The reference material was quartz but there were difficulties finding sufficient suitable quartz. Five different batches were obtained from the Merck company and tested for sensitivity, linearity and stability of the 340 degrees C peak, the 1992 batch was found to be the most appropriate.

The irradiations were performed at the Secondary Standard Dosimetry Laboratory at GSF using a Go-60 source as well as the in situ measurements with an ionization chamber, calibrated to the primary standards of PTB Braunschweig. Irradiated and unirradiated quartz was distributed to the five laboratories and although different procedures were used for thermoluminescence and optically stimulated luminescence, the source calibrations for the different laboratories agreed within +/-3% compared to the previous calibrations of the laboratories.