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Volume 26, Issue 11, November 1999
- PH. D. THESES ABSTRACTS
26(1999); http://dx.doi.org/10.1118/1.598776View Description Hide Description
Electron paramagnetic resonance(EPR) methodologies for radiationdosimetry are investigated using various dosimeter materials. Specifically, methodologies were developed and used which were intended to improve the accuracy and precision of EPR dosimetric techniques, including combining specimen rotation during measurement, use of an internal manganese standard, instrument stabilization techniques, and strict measurement protocols. Characterization and quantification of these improvements were performed on three specific EPR dosimeter materials. The dosimeter materials investigated were walrus teeth, human tooth enamel, and alanine dosimeters. Walrus teeth showed the least desirable properties for EPRdosimetry yielding large native signals and low radiation sensitivity. The methods for tooth enamel and alanine resulted in large improvements in precision and accuracy. The minimum detectable dose (MDD) found for alanine was approximately 30 mGy (three standard deviations from the measured zero dose value). This is a sensitivity improvement of 5 to 10 over other specialized techniques published in the literature that offer MDDs in the range of 150–300 mGy. The accuracy of the method on tooth-enamel was comparable to that typically reported in the literature although the measurement precision was increased by about 7. This improvement in measurement precision enabled a more nondestructive testing evaluation procedure to be developed (where the whole sample need not be additively irradiated in order to calibrate its radiation sensitivity). Using this virtually nondestructive evaluation procedure on numerous samples showed that the method could reconstruct the same doses to within 10 mGy of those evaluated destructively. Doses used for this assessment were in the range of 100–250 mGy.