A SQUID-based primary noise thermometer for low-temperature metrology

Area of Science:

• Physics
• Metrology
• Thermodynamics

Background:

• Accurate temperature measurements are crucial for scientific advancement and require traceability to international standards.
• The upcoming redefinition of the kelvin based on the Boltzmann constant necessitates advanced primary thermometry methods.
• Existing methods face limitations in the broad temperature ranges required for fundamental research.

Purpose of the Study:

• To develop and validate a novel DC superconducting quantum interference device-based noise thermometer.
• To enable primary thermometry for the realization and dissemination of the kelvin.
• To measure thermodynamic temperature accurately across a wide range, from 5 K down to below 1 mK.

Main Methods:

• Development of a DC superconducting quantum interference device (SQUID) based noise thermometer.
• Detailed description of the primary magnetic field fluctuation thermometer and its underlying thermodynamic temperature determination model.
• Experimental validation through comparison with the Provisional Low Temperature Scale 2000 (PLTS-2000).

Main Results:

• The developed thermometer successfully measures thermodynamic temperature in the range of 0.7 K to 16 mK.
• Experimental results show excellent agreement with the PLTS-2000.
• A relative combined standard uncertainty of 0.6% was achieved for the thermodynamic temperature measurements.

Conclusions:

• The DC SQUID-based noise thermometer is a viable primary thermometry technique for realizing and disseminating the kelvin.
• This instrument provides accurate thermodynamic temperature measurements in the millikelvin range with low uncertainty.
• The findings support the transition to a new SI definition of temperature based on fundamental constants.