The VNIIFTRI magnetic temperature scale is compared with the provisional low-temperature scale (PLTS-2000), based on the melting pressure of He-3, in the 0.37–0.56 K range. The magnetic temperature scale is reproduced from the readings of a rhodium-iron alloy resistance thermometer. The disagreement between the scales does not exceed 0.23 mK.

A thermodynamic temperature scale in the range 0.3–3 K is established by a magnetic method. The results of investigations enable the range of the State Standard of temperature to be extended from 0.8 K to 0.3 K with a simultaneous increase in its accuracy by a factor of 2–3.

Self-calibrated resistance thermometers to be used as standards have been investigated. The heat exchange of the sensor coil with liquid helium per unit coil surface area at 0.3 K is 12 times better than that of a conventional gas-filled thermometer. The exchange is due to Kapitza surface thermal resistance. The λ point in liquid helium filling of the thermometer is reproducible to within 0.1 mK.

Self-calibrated resistance thermometers to be used as standards have been investigated. The heat exchange of the sensor coil with liquid helium per unit coil surface area at 0.3 K is 12 times better than that of a conventional gas-filled thermometer. The exchange is due to Kapitza surface thermal resistance. The lambda point in liquid helium filling of the thermometer is reproducible:to within 0.1 mK.

A thermal flowmeter of gaseous helium with a linear scale and an upper flow rate limit of 450 mu mol/s is described. The error of measurement is 5% of the upper limit.

Mechanical creep of the diaphragm is well recognized as a major problem for obtaining a reproducible cryogenic pressure transducer and it is mainly caused by the stress at the diaphragm edge, where this is rigidly constrained to the transducer body. The double-diaphragm design alleviates this problem. In this design, the rigid constraint of the diaphragm edge is replaced by a (non-ideal) hinge between two identical diaphragms, which allows for a considerable improvement of the reproducibility on thermal cycling. Sapphire has normally been used for this design because of its excellent elastic properties. However, the quality of the results critically depends on technological details of the fabrication. The paper describes the design criteria used for the actual implementation of the double-diaphragm technique, making use of monocrystal sapphire disks of limited dimensions (O 25 mm). Results on the stability for Ap = 0 of a capacitive prototype (0. 1 bar f.s., sensitivity 1.35.10 -3 pF Pa -1 ), designed mainly for work in the range 3-30 K with a gas thermometer in the differential mode, showed a nearly zero temperature coefficient in that range, a zero shift decaying logarithmically with thermal cycling between 77 K and 300 K and limited to 0.025%, and a creep limited to 50 ppm in 8 days at 80-95 K.

Mechanical creep of the diaphragm is well recognized as a major problem for obtaining a reproducible cryogenic pressure transducer and it is mainly caused by the stress at the diaphragm edge, where this is rigidly constrained to the transducer body. The double-diaphragm design alleviates this problem. In this design, the rigid constraint of the diaphragm edge is replaced by a (non-ideal) hinge between two identical diaphragms, which allows for a considerable improvement of the reproducibility on thermal cycling. Sapphire has normally been used for this design because of its excellent elastic properties. However, the quality of the results critically depends on technological details of the fabrication.The paper describes the design criteria used for the actual implementation of the double-diaphragm technique, making use of monocrystal sapphire disks of limited dimensions (empty set 25 mm). Results on the stability for Delta p = 0 of a capacitive prototype (approximate to 0.1 bar f.s., sensitivity 1.35.10(-3) pF Pa-1), designed mainly for work in the range 3-30 K with a gas thermometer in the differential mode, showed a nearly zero temperature coefficient in that range, a zero shift decaying logarithmically with thermal cycling between 77 K and 300 K and limited to approximate to 0.025%, and a creep limited to 50 ppm in 8 days at approximate to 80-95 K.

In agreement with a prediction of the theory, we have observed experimentally the intrinsic quadrupole electric field of a centrosymmetric crystal.

A new version of the VNIFTRI gas-thermometric scale has been established on the basis of new measurements of the thermal expansion of copper used to make the bulbs of gas thermometers. Scales MPTSh-68 and MTSh-90, differing from the international temperature scales, are established for the range from 13 to 308 K.

New measurements of the thermal expansion of the copper used to manufacture the VNIIFTRI gas thermometer were performed and the temperature scale was corrected. The deviations of recalculated T(gas) scale from the IPTS-68 scale and from the ITS-90 scale in the range 13 K to 308 K were found.

We report the results of an experimental study of the external magnetic field of an antiferromagnetic Cr2O3 single-crystal. They confirm reliably that this field corresponds to a magnetic quadrupole field, as predicted by Dzyaloshinskii [Solid State Comm. 82, 570 (1992)] and observed by D. N. Astrov and N. B. Ermakov [JETP Lett. 59, 297 (1994)]. The quadrupole moment of the sample was found to be several times smaller than the value predicted by calculations.

We describe standard resistance thermometers made of a rhodium-iron alloy designed for operation in the temperature range 0.02-2 K. The sensitive element of the thermometer is filled with liquid helium-4 or helium3, which improves the heat exchange by several orders of magnitude. This makes it possible to significantly increase the measuring current and to use conventional technology for precise measurement of resistance.

Experimental confirmation has been found for Dzyaloshinskii's theoretical prediction [Solid State Commun. 82, 579 (1992)] that a magnetoelectric crystal would have an intrinsic quadrupole magnetic field.

An intercomparison between the primary pressure balance of the LNE and a mercury manometer developed at the All-Russian Research Institute for Physical, Technical and Radio-Technical Measurements (VNIIFTRI) for purposes of temperature measurement was undertaken in 1990. A short description of the two standards is given. The transfer standard was a pressure balance equipped with a piston-cylinder assembly that has the same characteristics as the standard of the Laboratoire National d'Essais (LNE). The results obtained from 30 kPa to 110 kPa showed a systematic relative difference of 12 parts in 106 between the two standards. This difference is significant, as the combined relative uncertainty at 1 σ level is estimated to be 4,2 parts in 106. These results are analysed in this paper.

The paper describes a cut-off valve whose volume changes by less than 0.2 mm(3) during operation, it was designed to handle pure gases.

As a part of preparatory work for the establishment of the new ITS-90 temperature scale, measurements of thermodynamic temperature by means of a gas thermometer without "dead space" were performed. The deviation of the NPL-75 scale from thermodynamic temperature was found to lie between zero and 0.7 mK. The value for the thermodynamic temperature of the hydrogen normal boiling point was found to be only 0.6 mK higher than that of Berry. The deviation of our scale, referenced to 273 K, from that of Steur and Durieux does not exceed 0.4 mK from 4.2 K to 27 K. Independent values of the second virial coefficient in the range 2.5 K to 27 K were found. In agreement with the results of other workers the deviations of the IPTS-68 from thermodynamic temperature were found to be - 8 mK near 20.3 K and +11 mK near 83 K. The maximal deviation of the IPTS-68 from thermodynamic temperature, viz 15 mK, was found near 150 K. This result is 4 mK higher than that of Kemp et al and lower by the same amount than was measured by the total radiation thermometer of Martin et al. The new values found for the thermodynamic temperatures of the fixed points are in good agreement with the results of other workers. The reference function W(T) for a standard platinum resistance thermometer is calculated.