Fluctuations of the Weight Indicated by a Microbalance in the Pressure Range Between 1 and 103 torr with the Sample at a Lower Temperature than the Beam

Large fluctuations in the indicated weight of up to 0.1 Hz frequency and 50 µg amplitude, were observed when using a vacuum microbalance with suspended pans, of which one was cooled to 77 K and the balance beam kept at room temperature. The amplitudes increased with increasing pressure and temperature difference between sample and beam. In a nitrogen atmosphere, the fluctuations began at 200 torr, and in an argon atmosphere at 140 torr, while in helium and hydrogen no fluctuations were observed. When the balance pan was empty, the fluctuations were particularly large, and when loaded, they generally decreased. With horizontally suspended disks and vertical tubes, practically no fluctuations were observed.