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Published on: May 9, 2014
Evaluation of monthly variations in electrometer calibration coefficients using a charge generator for radiation
Motohiro Kawashima1, Maria Varnava2, Shuichi Ozawa3,4,5
1Gunma University Heavy Ion Medical Center, 3-39-22 Showa-Machi, Maebashi, Gunma, 371-8511, Japan. mkawashi@gunma-u.ac.jp.
Abstract:
Electrometers are important devices that are part of the standard dosimetry system. Therefore, we evaluated the variation of electrometer calibration coefficients (kelec) over 1 year in this study. We investigated two types of electrometers: a rate mode and an integrate mode. Each electrometer was connected to a charge generator, a constant charge was applied, and kelec was determined by measuring the current. The current measurements were repeated once a month. For electrometers with multiple ranges, measurements were taken at low and medium ranges. Almost all kelec measurements agreed within 0.2% of the initial measurements. However, the low range of the electrometer with an integrate mode showed seasonal variation, with a variation greater than 0.2%. This study shows that electrometers may exhibit errors that cannot be detected through annual inspections. The importance of quality assurance using a charge generator at one's own institution was demonstrated.
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