Reference measurements of SQUID-based magnetic-field fluctuation thermometers

The magnetic-field fluctuation thermometer (MFFT) is a noise thermometer that has been developed for thermometry in sub-Kelvin refrigerators. Meaningful MFFT operation requires a prior measurement at one known temperature in the temperature range of operation. From this reference measurement a set of calibration parameters is determined that characterizes the thermometer. Aiming at improving the measurement quality of the MFFT and extending its acceptance, we have developed a setup and procedure for reference measurements at temperatures directly traceable to the PLTS-2000. The reference measurements allow the assessment of methods to determine the uncertainty of a MFFT measurement. Temperature measurements with relative uncertainties of <1% can be obtained within measurement times of ?10?s.