Absorbed Dose Rate in Air at the NIFS Site before the Deuterium Plasma Experiment in LHD

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The absorbed dose rate in air was measured at the National Institute for Fusion Science (NIFS) site before the deuterium plasma experiment in the Large Helical Device (LHD). A pocket survey meter was used for the measurement of 1cm dose equivalent rates in units of µSv h⁻¹ and these results were converted to absorbed dose rates in air (units: nGy h⁻¹) using a conversion factor. The arithmetic mean of the absorbed dose rates in air based on 257 measurement points at NIFS site was 45 nGy h⁻¹. The result of this study suggests that the building material and/or paving stone enhance the dose rates in air at the NIFS site.