Implementation of a programmable Josephson voltage standard in a zero boil-off dewar

MSL has successfully operated a programmable Josephson array system based on a NIST 2 V chip. The system is required for MSL's watt balance under development and involves a custom cryoprobe in a zero boil-off dewar. The design of the cryoprobe and its performance will be described. For example, at the optimum microwave power of 18.6 GHz and with all chip subarrays biased, a 1.34 mA step width of the quantized voltage was obtained at 4.25 K. In this mode the cryocooler maintained reserve cooling power of approximately 100 mW.