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Intrinsic Characteristics of the Nine Detectors and Evaluation of Their Performance in Non-Equilibrium Radiation Dosimetry

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M Markovic

M Markovic1*, S Stathakis1 , I Jurkovic1 , P Mavroidis1,2 , N Papanikolaou1 , (1) University of Texas Health Science Center, UTHSCSA, San Antonio, TX, San Antonio, Texas, (2) University of North Carolina, Chapel Hill, NC


SU-E-T-512 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

The aim for the study was to compare intrinsic characteristics of the nine detectors and evaluate their performance in non-equilibrium radiation dosimetry.

The intrinsic characteristics of the nine detectors that were evaluated are based on the composition and size of the active volume, operating voltage, initial recombination of the collected charge, temperature, the effective cross section of the detectors. The short-term stability and collection efficiency has been investigated. The minimum radiation detection sensitivity and detectors leakage current has been measured. The sensitivity to changes in energy spectrum as well as change in incident beam angles were measured an analyzed.

The short-term stability of the measurements within every detector showed consistency in the measured values with the highest value of the standard deviation of the mean not exceeding 0.5%. Air ion chamber detectors showed minimum sensitivity to change in incident beam angles while diode detectors underestimated measurements up to 16%. Comparing the slope of the tangents for detector’s sensitivity curve, diode detectors illustrate more sensitivity to change in photon spectrum than ion chamber detectors. The change in radiation detection sensitivity with increase in dose delivered has been observed for semiconductor detectors with maximum deviation 0.01% for doses between 1 Gy and 10 Gy. Leakage current has been mainly influenced by bias voltage (ion chamber detectors) and room light intensity (diode detectors). With dose per pulse varying from 1.47E⁻4 to 5.1E⁻4 Gy/pulse the maximum change in collection efficiency was 1.4% for the air ion chambers up to 8% for liquid filled ion chamber.

Broad range of measurements performed showed all the detectors susceptible to some limitations and while they are suitable for use in broad scope of applications, careful selection has to be made for particular range of measurements.

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