Use of a Resistive SQUID for Noise Thermometry
The recently-developed international temperature scale, ITS 90, does not extend below 0.65K. However, a considerable body of research, particularly that devoted to defining the physical properties of liquid 3He, has been conducted below this temperature without benefit of a common temperature scale. Accordingly, we have been developing a temperature scale in this region. The primary thermometer used in this effort is a special form of noise thermometer consisting of a resistively- shunted Josephson junction, or an R-SQUID. The R-SQUID offers advantages over conventional analogue noise thermometry in that the influence of the measuring circuits on the measured noise temperature is considerably reduced. A review is given of the decade of experience gained at NIST in the operation of this thermometer and in modelling its systematic errors. The reproducibility of the temperatures measured using the R-SQUID noise thermometer will also be presented, as well as comparisons of the noise temperature scale with scales defined by other thermometers.
KeywordsJosephson Junction Noise Temperature Johnson Noise Noise Thermometer Cerium Magnesium Nitrate
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