Abstract

The accurate measurements of low doses using EPR dosimetry with alanine are highly challenging due to the weak EPR dosimetric signal from low dose alanine, measurement errors due to the sample anisotropy in crystalline alanine, and the background signals from sample impurities. This study explores the feasibility of using the dose spiking EPR technique to overcome these challenges and decrease the detection limit in a low dose measurement using EPR. The measurement errors from the sample anisotropy were reduced by rotating the samples relative to the constant magnetic field direction using a goniometer and averaging the resulting EPR spectra. However, this technique only reduces the measurement errors in the high dose measurements, but it was ineffective in decreasing the measurement errors and dose detection limit at the low doses (20 - 220 mGy). As a result, the measurement accuracy obtained at the high dose (4 Gy) was exploited to increase the accuracy at the low doses using the dose spiking EPR technique. In this method, the low-dose alanine sample, undetectable and not reliably measurable in the X-band CW EPR spectrometer, spikes with a high dose (4 Gy). Then, the total dose was measured and subtracted from a spike dose to get the initial low dose. Using this technique, the low-dose alanine samples were measured with reliable precision. As a result, we concluded that this method has great potential to solve the low dose measurement problems in alanine.

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