The BIPM Compact Josephson Voltage Standard

Fifteen National Metrology Institutes have recently confirmed their interest in participating in the International Bureau of Weights and Measures (BIPM) direct on-site comparison of Josephson array voltage standards at the level of 10 V. This comparison has been ongoing since 1994, and the BIPM primary standard involved needs to be replaced by a new standard built from components based on modern technology. We present here in detail the components of the new BIPM Josephson voltage standard. The main goal during its development was to realize a standard that is more easily transportable, more convenient to use, and as efficient and reliable as its predecessor. Both primary standards have already shown agreement within a total combined relative uncertainty of 1.4 × 10^-10 (k = 1).