| Ion implanted silicon thermistors have been used successfully as thermometers for high-resolution X-ray microcalorimeters. The energy resolution obtained, however, has not generally been as good as that predicted by the thermodynamic model for a calorimeter with an ideal resistive thermometer. The 1/f noise of the thermometer is thought to be one of the main causes of this observation, but its effect has never been quantified before. This noise can have a significant effect on detector performance, and needs to be taken into account in the design optimization of infrared bolometers and X-ray microcalorimeters.;The intrinsic 1/f noise of ion-implanted silicon thermistors with doping density parameters, T0, ranging from 1.4 to 43 K have been characterized in the 0.05--0.5 K temperature range using an adiabatic demagnetization refrigerator. These measurements show that the noise can be reasonably well fit as DeltaR/R fluctuations whose spectral density varies as 1/f and whose magnitude increases steeply with lower doping density and lower temperatures. An arbitrary analytic approximation to the observed 1/f noise was obtained. Measured noise levels show quite good reproducibility for the 1/f noise behavior for devices of the same type. Good agreement has been found with measurements of devices made in other facilities (NASA Goddard Space Flight Center and INFN, Italy) according to somewhat different recipes. |
