PRMI Temperature Scale in the Range from 4,2 K to 20 K

Abstract

In 1964 the authors published preliminary results of their work on establishing the practical temperature scale in the temperature range from 4.2 K to 20 K. The temperature scale for this range was defined using a germanium resistance thermometer, as its sensitivity and reproducibility of readings are as good as it is required for the most accurate determinations of temperature. At the same time germanium thermometers have noticeable defects among which the main one is non-reproducibility of temperature dependence of its resistance from sample to sample, but no better thermometers for this range are available now.The results of the well-known works on establishing IPTS in the temperature range from 12 K to 273 K show that even the platinum-thermometers cannot be fitted a sufficiently simple analytical resistance-temperature function. The only method which appears to be acceptable for semiconductor resistance thermometers is the table method.The establishment of a temperature scale by any method possible involves calibration of the secondary (in our case germanium) thermometers against a primary device reproducing the thermodynamic temperature scale. As a primary instrument we used a gas thermometer without a dead space. Four thoroughly examines germanium thermometers formed a standard group, conserving a temperature scale defined by individual curves T = T(W) for each thermometer of the standard group (the resistance ratio W = RT/RH2). Based on smooth W(T) tables, obtained as a result of the standard thermometers' calibration against the gas thermometer, tables have been made, to be used for converting resistance values of the standard thermometers into temperature values.The temperature in our scale is defined as an average of readings of the standard group thermometers. This paper presents a detailed description of the work on establishing the temperature scale.