THIN-FILM ALANINE-POLYETHYLENE DOSIMETER

A thin-film dosimeter was prepared by homogeneously mixing ground DL-alpha-alanine crystalline powder and melted low-density polyethylene and by subsequent extrusion into a long tape with 8 mm width. The basic dosimetric characteristics of the 200-mum thick film dosimeter were studied for Co-60 gamma-rays and 2.0-MeV electron beams. Dose responses were measured using a conventional electron spin resonance (ESR) spectrometer as well as a custom-made compact reader. The ESR measurement procedure was improved by the design of a dosimeter holder for high reproducibility, which avoided the orientation effect of samples during ESR readings. The random uncertainty of dose response among 20 irradiated replicate dosimeters is +/- 1 % (1sigma) for absorbed doses of 10(3)-10(5) Gy, with correction being made for the weight differences of the dosimeters. The measurable dose range using the conventional ESR spectrometer is from 0.05 to 100 kGy. The compact reader can also be applied for dose evaluation above 1 kGy, with a precision within 1 %, covering the measurable dose ranges of both FWT-60 radiochromic film and cellulose-triacetate film dosimeters. The estimated dose derived from two calibration curves for gamma-rays and electron beams was in good agreement. The thin-film polyethylene-alanine dosimeter can be useful as a reference dosimeter for medium energies of electron beams (approximately 2 MeV) as well as for comparison of radiation effects on various materials for photons and electron beams.