The new interferometer of the BIPM watt balance

This paper reports on the new 3-axis interferometer for the velocity measurement for the BIPM watt balance. The frequency of a commercial Nd:YAG 532 nm laser has been stabilized to a hyper fine transition in iodine by saturated absorption techniques. The interferometer was first mounted, aligned and characterized in a separate test bench. The whole experimental set-up was then transferred to the watt balance laboratories. The new interferometer is at present being integrated and aligned inside the watt balance apparatus.