Noise Measurements of the Lowest Frequency Longitudinal Mode of an Aluminum Cylinder at Liquid Nitrogen Temperatures.

摘要

The lowest frequency longitudinal mode of an aluminum cylinder has been studied over the temperature range 60K - 78K. Lead zirconate titanate crystals were bonded to the cylinder for observation of the thermal fluctuations, and relaxation phenomena. Large amounts of excess noise were observed whenever the cylinder was not in thermal equilibrium. The cylinder appeared to have attained thermal equilibrium after its temperature had been maintained near liquid nitrogen temperatures for several weeks. Noise temperatures within a factor 2 of the temperature measured by a platinum resistance thermometer were observed when the mean temperature of the cylinder was drifting less than 0.01 degree Kelvin per day. The very large fluctuations in noise temperature are not understood and warrant further investigation. (Author)