Effect of Room Temperature Changes on Gravity Observation with Superconducting Gravity Meters.

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  • 超伝導重力計を用いた重力観測に及ぼす室内温度変化の影響
  • チョウデンドウ ジュウリョクケイ オ モチイタ ジュウリョク カンソク ニ オ

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Abstract

Spatial and temporal variations of room temperature in the gravity observation room of Kyoto University were investigated with 13 quartz thermometers for clarifying the effect of room temperature changes on precise gravity observation with superconducting gravity meters. Observational data of room temperature and gravity in July 10, 1993-July 9, 1994 were analyzed. Although the air conditioner has not been operating in the observation room, annual and diurnal changes of room temperature are 10°C and 0.2°C at the most, respectively. Ratios of these changes to atmospheric temperature changes were about 0.5 and 0.03, respectively. The effect of room temperature changes on gravity observation is considered to be caused by thermal expansion of piers of gravity meters, movements of the tilt control system depending upon temperature changes, as well as thermal noise of electric circuits. Gravity changes due to thermal expansion of piers are in the order of a few ngals in a year and 0.01 ngal in a day at the most. Those due to movements of the tilt control system depending upon temperature changes are lower than 1 ngal. On the other hand, thermal noise of electric circuits might cause gravity changes in the order of 1 Fugal in proportion to annual change of room temperature. In a period band shorter than a few days, however, it causes gravity changes by 0.01 μgal at the most. Therefore, the effect of room temperature changes on gravity observation can be ignored in that shorter period band, even if the air conditioner is not used.

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