Evaluation of a salicylic-acid-based Fricke gel for gamma radiation dosimetry.

Three-dimensional dosimetry enables the assessment of spatial dose distributions, which is particularly important in radiation processing and medical applications. Among chemical dosimeters, the Fricke system is widely recognized as a reference standard based on its reliability and well-established response mechanisms. Various modifications to this system, including the incorporation of gel matrices and optical indicators, have expanded its applicability to volumetric dose measurements. In this study, a modified Fricke gel dosimeter using salicylic acid as an ion indicator (FSG) was developed and characterized. The dosimeter response was evaluated after irradiation with a cobalt-60 gamma source. Optical analysis was conducted using spectrophotometry to determine the dose-response behavior over the range from 5 to 200 Gy. The results reveal a linear relationship between absorbance and absorbed dose within the investigated range. When compared with the conventional Fricke xylenol gel (FXG), the proposed formulation exhibits a broader dynamic range, with no saturation observed up to 200 Gy. Although FXG exhibits higher initial sensitivity, it reaches saturation at significantly lower doses. Additionally, the temporal stability of the dosimeter response was investigated through spectrophotometric measurements, which were performed up to 24 h after irradiation. The results indicate time-dependent behavior, with an initial increase in absorbance, followed by a gradual signal decrease. These findings indicate that salicylic acid is a viable and promising alternative as an ion indicator in Fricke gel dosimeters, offering advantages such as low cost, accessibility, and reduced toxicity.