Thin film alanine-PE dosimeter for electron beam transfer dosimetry

Abstract

Thin film alanine-PE dosimeter developed at CIAE is expected to be used as transfer dosimetry system particularly for electron beam dose measurement. Its basic dosimetry characteristics were studied under 60Co γ-ray and electron beam irradiation. The investigated dose range was between 20 and 3×10 5 Gy. The background dose for the unirradiated dosimeter was about 4 Gy. The inter-specimen scattering among 10 replicate irradiated dosimeters was less than 0.6% ( 1 σ ) for the doses of 1 kGy after correction of weight differences of dosimeters. The ratio of EPR signals from two batches was about 1.0091±0.0049 ( 1 σ ) for 15 dose points from 70 to 40 kGy. No significant dose response dependent on energy or dose rate was found in both γ-ray irradiation (average energy 1.25 MeV, dose rate down to 0.4 Gy/s) and electron beams irradiation (energy up to 14 MeV, dose rate to 10 8 Gy/s). The irradiation temperature coefficient was about 0.26%/°C between 15 and 50 °C in the dose range from 5 to 50 kGy. Another important feature, post-irradiation stability, was also studied in detail for dosimeters stored at 4 °C, room temperature and 40 °C with relative humidity of 98%, 76%, 58%, 33% and 12%. Uncertainty of the dosimetry system for electron beam dose measurement was 2.9% ( k = 2 ) for dose from 10 2 to 10 4 Gy, while 5.6% ( k = 2 ) for dose higher than 10 4 Gy. The preliminary inter-comparison results between CIAE alanine-PE/EPR dosimetry system and the reference dosimetry systems from RISO, JAERI and INCT were comparable within their combined uncertainty, which showed the potential of CIAE alanine-PE/EPR dosimetry system to be used as transfer dosimetry system.