The Effects of Ambient Conditions of Cesium Clock Rates

Abstract : The rates and errors of 42 cesium clocks in 6 different vaults at USNO were studied using 18 months of hourly data. Temperature effects were found to be negligible when the temperature was controlled to within plus or minus 1 degree C. During excursions much greater than this, rate changes in either sense are possible. No short-term humidity effects were evident, but there appears to be an annual variation in clock rates (in either sense) dependent on absolute humidity. Significant intercorrelations between clocks indicate the general importance of environmental conditions of some kind.