A correction method between sample mass and EPR intensity in radiation dose reconstruction

Abstract

In electron paramagnetic resonance (EPR) radiation dose reconstruction, maintaining a consistent mass across a series of aliquots is crucial. However, due to sample limitations or experimental uncertainties, achieving this consistency may not always be possible. To address these challenges and optimize experimental processes, a theoretical model ($I-M$ model) was developed to describe the relationship between EPR intensity emanating from a TE₀₁₁ mode cylindrical resonant cavity and sample mass. The model was verified using the TEMPO paramagnetic standard and quartz, a common material employed in dosimetry reconstructions. Based on this model and the evaluation of the modulation magnetic field uniformity, correction methods for EPR intensity in solid powder samples were proposed. The model reveals that the non-uniformity of the microwave magnetic field distribution in the resonant cavity leads to spatial inconsistency in sample responses, resulting in a non-linear relationship between EPR intensity and sample mass, characterized by a “sinusoidal + linear” pattern. The parameter $I_{\mathrm{cen.}}$ is recommended as a metric for EPR intensity, as it intrinsically characterizes the spin concentration of the sample regardless of sample mass, thereby enhancing the accuracy of quantitative EPR measurements and equivalent dose evaluation.