電子天びんを用いた真空中でも質量測定 Mass Measurement in Vacuum Using an Electronic Mass Comparator
A new electronic mass comparator, capable of automatic weighing in vacuum, was introduced into the National Research Laboratory of Metrology. The standard deviation of 0.1 μg, a factor of 3 smaller than the standard deviation of the best previous measurement using a mechanical balance, was achieved for the mass comparison between two 1-kg weights. For eight days, mass difference of two 1-kg weights with the surface area difference of 66.7 cm<SUP>2</SUP> was measured in vacuum. We observed an outgassing rate of 9×10-<SUP>6</SUP> Pa·<SUP>3</SUP>·s<SUP>-1</SUP>·m<SUP>-2</SUP> after an evacuation for 3.9-6.8 hours, and below 6×10<SUP>-9</SUP> Pa·m<SUP>3</SUP>·s<SUP>-1</SUP>·m<SUP>-2</SUP> after an evacuation for 107 hours. Residual gas in the vacuum chamber, which housed the electronic mass comparator, was analyzed to monitor the oil contamination. At a total pressure of 5.5×10<SUP>-4</SUP> Pa, we observed the main peaks due to hydrocarbon at 41, 43, and 57 amu with a partial pressure of 3×10<SUP>-6</SUP> Pa.
真空 43(3), 181-183, 2000-03-20
The Vacuum Society of Japan