The NASA/GSFC Hydrogen Maser Program: a Review of Recent Data

Mary Chiu, Alvin G. Bates, Lauren J. Rueger, Victor S. Reinhardt, Peter Dachel, Richard Kunski, Robert Kruger, S. Clark Wardrip

Abstract:	The NASA/Goddard Space Flight Center Hydrogen Maser Program has had as goals for many years the development of improved field operable hydrogen masers, the improvement of existing field operable hydrogen masers and the development of novel hydrogen maser frequency standards. This paper presents a review of recent data, taken both in the laboratory and in the field, in these areas. Data is presented on the phase and frequency stability, over time periods extending to one week, of the new NR field operable hydrogen masers developed by the Applied Physics Laboratory (APL) and the older NX and NP field operable hydrogen masers developed by Goddard Space Flight Center and maintained and upgraded by Bendix Field Engineering Corporation (BFEC). Data is presented on the NR masers in the laboratory showing frequency stabilities well into the 10- range and phase stabilities well into the 100 psrange for periods of up to one day. Data is presented on upgraded NP masers in the laboratory showing that the frequency stability has been improved substantially to virtually the NR level. VLBI data is presented on the phase difference between NX-2 at Owens Valley, California and NR-2 at Fort Davis, Texas for a one week period showing, after removal of a constant frequency drift, a 350 ps RMS phase stability. The role of a temperature control chamber for hydrogen masers developed by BFEC in improving the long term stability of hydrogen masers is discussed. Extensive development work is being performed by both APL and BFEC to improve the performance of hydrogen masers beyond their current levels. A quartz cavity liner designed to retrofit into existing NR, NP, and NX microwave cavity structures has been developed by BFEC and APL in a cooperative effort. This liner has been installed in an NR maser and has been shown to reduce the cavity temperature coefficient by a factor of 8. Data is presented showing the stability of this maser against other NR masers. A completely quartz cavity and storage bulb structure, called the integral cavity, which will also retrofit into the NR, NX, and NP masers is being developed by BFEC and APL in another cooperative effort. This structure should reduce the cavity temperature coefficient by a factor of 25 or more and should improve the maser's frequency stability under mechanical shock. Data is presented on the recent progress in the development of an external bulb variable volume hydrogen maser primary frequency standard.
Published in:	Proceedings of the 14th Annual Precise Time and Time Interval Systems and Applications Meeting November 30 - 3, 1982 NASA Goddard Space Flight Center Greenbelt, Maryland
Pages:	421 - 449
Cite this article:	Chiu, Mary, Bates, Alvin G., Rueger, Lauren J., Reinhardt, Victor S., Dachel, Peter, Kunski, Richard, Kruger, Robert, Wardrip, S. Clark, "The NASA/GSFC Hydrogen Maser Program: a Review of Recent Data," Proceedings of the 14th Annual Precise Time and Time Interval Systems and Applications Meeting, Greenbelt, Maryland, November 1982, pp. 421-449.
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