Physics of Systematic Frequency Variations in Hydrogen Masers
SMITHSONIAN ASTROPHYSICAL OBSERVATORY CAMBRIDGE MA
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The frequency stability of hydrogen masers for intervals longer than 10000 seconds is limited at present by systematic processes. We discuss the physics of frequency-determining mechanisms internal to the maser that are susceptible to systematic variations, and the connections between these internal mechanisms and external environmental factors. Based upon estimates of the magnitudes of systematic effects, we find that the primary internal mechanisms currently limiting long-term maser frequency stability are cavity pulling, at the level of parts in 105 per day, and wall shift variations, at the level of parts in 10 to the 16th power to parts in 10 to the 15th power per day. We discuss strategies for reducing systematic frequency variations.
- Lasers and Masers