Integrated thin-film dc RSQUIDs for noise thermometry

Integrated thin-film de RSQUIDs (Resistive Superconducting QUantum Interfer ence Devices) have been developed that significantly simplify noise thermom eter operation. We show theoretically that the main equations for noise the rmometry deduced for rf RSQUIDs can also be applied to dc RSQUIDs. Our dc R SQUIDs can at least be operated down to 0.04 K. Between 0.14 and 5.9 K the measured noise temperature agrees with the temperature of calibrated refere nce thermometers. We investigate the errors and uncertainties of a dc RSQUI D noise thermometer, in particular errors due to excess noire, A model for excess noise and its impact on the noise temperature e is presented and sho wn to be in agreement with the measurements.