Preparation Condition and Dose—Response Characteristics of Thin-film Dosimeters Using Fine Grain Alanine Crystal

Development of thin-film alanine dosimeter is required for application of reliable alanine/ESR dosimetry technique to short-range radiation. Molding condition and dose-response characteristics of the dosimeters were studied in terms of fine-grain alanine crystal prepared by grinding and recrystallization, five different lowdensity polyethylenes (PE) as binders, and two different molding methods of press and extrusion. Physical characteristics of the dosimeter after molding depend on grain size and shape of alanine crystal, fluidity and solidity of binders, and molding methods. The thin film alanine dosimeters of 150-200μm in thickness, were manufactured by two methods: (1) press-molding of the mixture of recrystallized alanine powder and PE with high melt index (MI) value, and (2) extrusion of the mixture of ground alanine powder and PE with relatively low MI value. The former method (1) is useful to prepare thinner films, and the latter method (2) enables us to achieve higher precision of dose responses within ± 2 % (at 95% confidence level) for the dose range of1-100 kGy.