Demonstration of an ultra-stable temperature platform

We report on a new thermometer design and precision heater controller for use in cryogenic experiments near 2.2 K. The thermometer design reduces the thermal resistance between the thermometer and the liquid 4He sample to the point where the noise is limited by thermally driven electrical current fluctuations in the PdMn. The heater controller uses a series array of rfbiased Josephson junctions on a constant voltage state to precisely control the voltage drop across the heater resistor. This technology may be used to create a blackbody reference device with unprecedented stability.