Development of zener calibration system using 10 V programmable Josephson voltage standard at NMIJ

We are developing a calibration system for Zener voltage standards using a programmable Josephson voltage standard (PJVS) for the purposes of the reduction in liquid-helium consumption and also the improvement of the calibration performance. The PJVS array is composed of total 524 288 NbN-based Josephson junctions and is cooled with a 10 K compact cooler. For verifying the validity of the system, the indirect comparison between the PJVS system and our conventional JVS (CJVS) system has been carried out. As a result, the agreement within the relative expanded uncertainty of 7.8 × 10^-9 was obtained. The uncertainty in the calibration of Zener voltage standards using our PJVS system is also discussed.