Preliminary measurements of T-T90 using acoustic gas thermometer in neon gas

The measurements of the difference between the thermodynamic temperature T and the temperature T90 based on the International Temperature Scale of 1990 (ITS-90), (T-T90), by using an acoustic gas thermometer (AGT) working on neon gas is reported in this paper. The AGT introduced a one-liter quasi-spherical resonator made of oxygen-free-copper. The thermodynamic temperature was determined relatively from the speed of sound measurements at a desired temperature regarding to those at the triple point of water. At the present stage, the aimed temperature range was the gallium melting point. Based on the obtained measured speed of sound, the thermodynamic temperature T and the values of (T-T90) were determined, and the associated uncertainties were estimated. The (T-T90) obtained in the present work was found to agree within the estimated uncertainty with the currently reported values that exist in temperature range overlapping with the present work.