Fast Johnson noise thermometry using a temperature dependent sensor

Johnson noise thermometry is a well established technique that allows the determination of the temperature starting from the measurement of the thermal noise produced by a known resistance at thermal equilibrium. Notwithstanding that, under proper conditions, the Johnson noise thermometer is a primary thermometer, the very long measurement time that is required to reach accuracies in the order of a fraction of a Kelvin is possibly the main reason why it is used only in a limited set of application fields. Here we propose to employ a strongly temperature dependent device as a sensor, namely a semiconductor diode at equilibrium, in order to significantly reduce the measurement time. It will be shown how, by means of the simultaneous measurements of the noise produced by the sensor device (diode) and by a high accuracy and high stability reference resistor, the sensor can be calibrated with high accuracy. Preliminary results are presented demonstrating the effectiveness of the approach we propose and the possibility of reaching accuracies in the order of a small fraction of 1 K in the temperature range from 300 to 400 K.