ION Technical Content
Cryogenic Masers
| Abstract: | The long-term frequency stability of a hydrogen maser is limited by the mechanical stability of the cavity, and the magnitudes of the wall relaxation, spin exchange, and recombination rates which affect the Q of the line. Recent magnetic resonance studies of hydrogen atoms at temperatures below 1 K and in containers coated with liquid helium films have demonstrated that cryogenic masers may allow substantial improvements in all of these parameters. In particular the thermal expansion coefficients of most materials are negligible at I K. Spin exchange broadening is three orders of magnitude smaller at 1 K than at room temperature, and the recombination and wall relaxation rates are negligible at 0.52 K where the frequency shift due to the He-coated walls of the container has a broad minimum as a function of temperature. Other advantages of the helium-cooled maser result from the high purity, homogeneity, and resilience of the helium-film-coated walls and the natural compatibility of the apparatus with helium-cooled amplifiers, which are necessary to take advantage of the intrinsically low thermal noise of the cooled cavity. |
| Published in: |
Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 3, 1981 Naval Research Laboratory Washington, DC |
| Pages: | 547 - 562 |
| Cite this article: | Berlinsky, A.J., Hardy, W.N., "Cryogenic Masers," Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting, Washington, DC, December 1981, pp. 547-562. |
| Full Paper: |
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