Specific Heat Measurements in 1–10°K Range Using Continuous Warming Method

Abstract

We describe a system for measuring specific heats by a continuous warming method with accuracy at least as high as has been attained with the usual heat burst method. Using this system data can be obtained very rapidly, even by unskilled operators, and reduced to final form with straightforward analysis and small amounts of computer time. We analyze the method in terms of simple models which take into account uncertainties in the stray heat, thermal gradients in the specimen assembly, the effects of electrical noise and finite bandwidth in the thermometer circuits, and their relation to the measurement of small heat capacities. Data on lead, mercury, and gallium are presented which indicate that the models lead to fair estimates of the anticipated scatter once certain characteristics of the apparatus are known. The observed scatter varied from 0.3% for gallium, where electrical noise in the amplifiers was a dominant factor, to less than 0.1% for lead and mercury, where no single factor was conspicuous. In addition, completely independent measurements were reproducible to about 0.1%. In these experiments the measuring intervals were never greater than 1% of the absolute temperature.

Measuring small changes in calorimetric properties using a ’’direct difference’’ technique

“…10, and the conclusions drawn there remain basically unchanged when the direct difference technique is used. 10, and the conclusions drawn there remain basically unchanged when the direct difference technique is used.…”

Velocity of Sound at 1 MHz Near theHe4Critical Point

“…The calibration points were fitted to a four-parameter equation of the form 1/T = A log R +B/(log R+D) + C by a least-squares computer program. 22 Temperatures above the highest-temperature calibration point were determined by extrapolation. Since the range of extrapolation was only 0.1 to 0.…”

“…Since the range of extrapolation was only 0.1 to 0. 2°K and the fitting function has been found to represent the R(T) relation over a wide range of temperature, 22 this procedure introduces only a small error in the determination of temperature and most of the temperature uncertainty can be ascribed to uncertainties in the calibration itself.…”

A compensated heat-pulse calorimeter for low temperatures

“…The measurement of the temperature dependence of the heat capacity of a material is an often used means to achieve a first step into the understanding of its physical properties. Besides the adiabatic technique several nonadiabatic techniques, like the relaxation-time method, 1 the continuouswarming principle 2 or the ac-calorimetry 3 are used. For more details the reader is referred to review articles covering lowtemperature calorimetry.…”