A new interferometric system for the BIPM Kibble Balance

The paper describes a new interferometric system for measuring the coil displacement in the BIPM Kibble balance. The system has led to a significant reduction in both the type A and type B uncertainty of the Kibble balance measurement. Compared to the previous version, the new instrument doubles the measurement signal thanks to a novel design. The optical and mechanical set-up is more compact, more stable and less sensitive to vibration noise. It is also more easily aligned, particularly for adjusting the interferometer beams vertically.