Modern Gas-Based Temperature and Pressure Measurements

Since the beginning of the preparation of this volume, we have been convinced that temperature and pressure measurements should not be separated, particularly in different applications at low temperatures. This belief has made us deeply conscious of the fact that the advanced applications and modern experimental methods of investigation in science and technology need the combination of various professional experiences and approaches. Although the book is divided into two parts (Part I by F. Pavese and Part II by G. F. Molinar), we have tried to correlate low-temperature and low-pressure measurements as much as possible. We hope that our readers will find this book, which contains a large number of experimental and reference data, useful in their effort to solve measurement problems. We are pleased to acknowledge our debt to several persons and wish to express our gratitude to them for their valuable cooperation and help: to our research group colleagues at the Istituto di Metrologia "G. Colonnetti" -IMGC (CNR), without whom the knowledge and the experience we built up during many years could not have been acquired; to G. T. McConville, M. Durieux, and K. Grohmann for revisions of and various suggestions for Part I; to V. E. Bean and C. R. Tilford of NIST and G. T. McConville for revisions of and various suggestions for Part II; and to I. Prinetti of IMGC for many valuable suggestions and careful textual revisions.

Inhalt

List of Acronyms.- PART I: Temperature measurements in the range from 0.1 K to 300 K.- List of Symbols.- Introduction.- The concept of temperature.- Definitions of temperature.- The phenomenological approach.- The axiomatic approach.- The microscopic approach.- Negative and non-equilibrium thermodynamic temperatures.- Temperature scales.- Thermodynamic temperature.- Empirical temperature.- Semi-empirical scales.- Empirical scales.- Official temperature Scales.- The 'mise en pratique' of the kelvin.- Summary of a temperature scale definition.- Gas-based fixed points for thermometry.- Thermodynamic states versus standard reference materials.- Substances and standard reference materials.- Thermodynamic states and phase diagrams.- Reference points: triple, boiling and critical points.- Physics associated with gas triple points.- Triple point of a pure substance.- Triple point of an impure substance Cryoscopy.- Ideal solutions of solid-insoluble impurities.- Solid-soluble and isotopic impurities.- Eutectic, peritectic and other mixtures .- The realization of temperature fixed points using gas triple points.- Thermal problems in the design of triple point cells.- Vapour-pressure bulb-type cell, used with the dynamic technique.- Small cell with inner thermometer, used with the equilibrium technique .- Hydrostatic temperature gradient.- Chemico-physical problems in triple point realizations.- Purity.- Reactive substances.- Ortho-para composition.- Gas handling systems.- The technique of sealed cell for the realization of a temperature reference.- Cells with vapor-space extending to room temperature.- Totally cold cells.- Modern design of temperature fixed points based on the triple point of gases.- Sealed cells for capsule thermometers.- Single cell design.- Multiple-cell cells.- High enthalpy cells.- Sealed cells for long-stem thermometers.- Fixed points using other phase transitions.- Liquid-to-liquid transition.- Solid-to-solid transitions.- The ITS-90 between13.80 K and 273.16 K and Scale approximations using sealed fixed points.- Realization of the ITS-90 in the Laboratories .- Approximating the ITS-90.- Gaseous Standard Reference Materials and the sealed cells.- Summary of triple-point sealed-cell design criteria.- Summary of sealed-cell fabrication techniques.- Summary of the sealed-cell measurement procedures by step-melting.- Gas thermometry between 0.5 K and 273.16 K.- Constant volume gas thermometry.- Influence of physical parameters.- Virial coefficient.- Amount of 'active' substance.- Gas purity.- Influence of technical parameters.- The gas bulb.- Pressure measuring line.- Filling molar density.- Gas thermometer with built-in pressure measuring device.- Use of a CVGT with a differential cryogenic pressure transducer .- Use of a CVGT with an absolute pressure transducer.- The bulb volume of the gas thermometer.- Interpolating constant-volume gas thermometers.- ICVGT types with stipulation of the virial function.- Three-fixed point ICVGTs.- Two-fixed point ICVGTs.- Four-fixed point ICVGTs.- ICVGT types without stipulations.- Three-fixed point ICVGTs.- Two-fixed point ICVGTs.- Four-fixed point ICVGTs.- Gas thermometer realization.- CVGTs with reference at temperatures lower than 273.16 K.- Measuring bulb.- Pressure capillary.- Pressure measuring system.- Modern realizations.- CVGTs with reference temperature at 273.16 K.- CVGTs using a cryogenic pressure-measuring gauge.- Realizations of interpolating gas thermometers.- Gas thermometry in the ITS-90, and future development.- Dielectric-constant, refractive-index, and acoustic gas thermometers.- Dielectric-constant gas thermometer.- Refractive index gas thermometer.- Acoustic thermometer.- Summary of design criteria for an absolute CVGT in the low temperature range .- Summary of differences and simplifications in design criteria of an ICVGT.- Summary of the measurements procedures for an absolute CVGT in the low temperature range.- Summary of differences and simpl