MODELING FREQUENCY FLUCTUATIONS AND NOISE THERMOMETRY USING AN R-SQUID NOISE THERMOMETER

We have measured the white and additive noise generated by an R-SQUID noise thermometer whose temperature was varied from 6.3 mK to 0.738 K. We have also conducted room temperature simulations of the effect of white and additive noise on the circuit used to measure the noise for the R-SQUID. We generally found that the measured noise in all cases w as fit to within the 0.1% statistical measurement imprecision by a mod el for the R-SQUID based on frequency modulation. This conformity is s ufficiently good that any deficiencies in either do not lead to system atic inaccuracies in the noise temperature scale which exceed 0.1%. Co mparisons of the R-SQUID with several other thermometers indicate that the overall agreement is at worst 0.2%.