LAUSR

The article 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 setup is more compact, more stable, and less sensitive to vibration noise. It is also more easily aligned, particularly for adjusting the interferometer beams vertically.