Improved frequency stability of the dual-noble-gas maser

We report improved frequency stability of the dual-noble-gas maser. This recently developed device can measure very small changes in the Zeeman transition frequencies of cohabitating ensembles of Xe-129 and He-3 atoms, and thus may be useful for symmetry tests and precision measurements such as a search for a permanent electric dipole moment of the Xe-129 atom. Using the dual-noble-gas maser, we measured the frequency stability (i.e., the Allan deviation) of the 3He Zeeman transition to be approximately 100 nHz in 6000 s of data acquisition. This Zeeman frequency stability is an order of magnitude improvement over our previous report.