A Transportable Josephson Voltage Standard

The Army has actively participated in the development and application of quantum voltage standards since the US practical Volt was redefined by NIST in terms of the Josephson Effect in 1972. An Army-led collaborative effort resulted in the commercialization of Josephson array technology in the mi-1990s. Today, the Josephson Effect defines the SI representation of the Volt and Josephson-based systems serve as standards in national metrology institutes and primary laboratories throughout the world. An Army effort is currently underway to make quantum voltage metrology systems practical for use outside the primary standards laboratory by making them more robust, simpler to operate, and eliminating the requirement for liquid helium. The first prototype of a more practical quantum voltage standard is currently being tested at the Army Primary Standards Laboratory (APSL) in Alabama. The new voltage standard is compact, transportable, self-contained, and cryogenically-cooled. This paper describes the prototype and the results of performance tests, including indirect comparisons to the Army primary Josephson voltage standard.