Raman spectroscopy as a tool to evaluate oxygen effects on the response of polymer gel dosimetry

CHACÓN, D.; J. VEDELAGO; M. STRUMIA; M. VALENTE; F. MATTEA

APPLIED RADIATION AND ISOTOPES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2019 vol. 150 p. 43 - 52

0969-8043

Currently, advanced dosimeters like polymer gels are capable of reliable and accurate 3D dose distributions obtained from correlation with the different polymerization degrees induced by incident radiation. Samples of polymer gel dosimeters are commonly read out using magnetic resonance imaging or optical methods like visible light transmission or laser computed tomography. Alternatively, this work proposes and evaluates the implementation of Raman spectroscopy to provide direct information on the chemical changes of each monomer that polymerized, due to irradiation, for three types of polymer gel dosimeters, namely NIPAM, ITABIS and PAGAT. The aim of the present study is to provide better and complete interpretations using three different containers, adequate for integral, 2D and 3D dose mapping. Moreover, Raman spectroscopy has been used to analyze the well-known effect ofoxygen inhibition on the different polymer gel dosimeters remarking the importance of avoiding air exposition during sample storage and readout. Dose-response curves for different polymer gels were obtained in terms of measurements with a calibrated ionization chamber. Additionally, dedicated Monte Carlo simulations were performed aimed at characterizing dose rate for different X-ray irradiation setups, providing also suitable information to evaluate oxygen diffusion through the sample wall. The obtained results were contrasted with optical transmission readout as well as Monte Carlo simulations attaining very good agreements for all dosimeter types.