Single-state selection system for hydrogen masers.


We describe a single-state selection system for hydrogen masers based upon the adiabatic fast passage method of state inversion. The present design improves the vacuum performance over a previously reported system, and includes increased storage bulb collimation. The system provides line Q's up to 7.2 x lo9, and removes from the hydrogen beam approximately 90% of atoms in the F = 1, mF = 1 state. INTRODUCTION AND SYSTEM DESIGN In the hydrogen maser, hydrogen atoms in the F = 1, mF = 0 hyperfine state (called state "cn) are confined in a storage bulb where they make transitions to the F = 1, mF = 0 state (state "an). In masers with traditional state selectors, the state selection magnet removes from the atomic beam entering the storage bulb essentially all atoms in states "an and "bn (F = I , mF = I), leaving equal numbers of atoms in states "c" and "dn (F = 1, mp = 1). Atoms other than in state "c" do not contribute to maser oscillation, but cause undesired spin exchange relaxation of the radiating atoms, and can cause frequency shifts of the output signal[']. By eliminating the state "dn atoms from the beam, it is possible to reduce these undesirable effects and achieve increased frequency stability. We have designed a single-state selection system that removes approximately 90% of the state "d" atoms from the beam121. We describe here a system with improved construction, and discuss results obtained using the system. The single-state selection system consists of a traditional hexapole state selection magnet that removes atoms in states "an and "bn from the atomic beam, followed by a state-changing apparatus that inverts atoms in state "dn into the "bn state but leaves "c" atoms undisturbed. A second state selection magnet then removes the "bn atoms from the beam, leaving only the desired "cn atoms to enter the storage bulb. In our design, the state changing mechanism, which operates on the adiabatic fast passage (AFP) principle,13] consists of two electromagnets, shown in Fig. 1: a longitudinal variable-pitch solenoid that creates a DC magnetic field varying in intensity along the beam path between roughly 0.3 and 3 gauss, and a transverse four-wire coil, mounted within the solenoid, that produces an RF magnetic field with a frequency on the order of 2 MHz. In the present design the statechanging coils are wound on six aluminum oxide tubes secured to an aluminum framework by molybdenum snap rings. The low vapor pressure materials used minimize the evolution of background gases that can contribute to beam scattering, while the open construction allows increased pumping speed in the beam region. These characteristics permit the use of increased beam flux, thus improving the short-term frequency stability attainable. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE DEC 1987 2. REPORT TYPE 3. DATES COVERED 00-00-1987 to 00-00-1987 4. TITLE AND SUBTITLE Single State Selection System for Hydrogen Masers 5a. CONTRACT NUMBER

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@article{Mattison1987SinglestateSS, title={Single-state selection system for hydrogen masers.}, author={Edward M. Mattison and Robert F . C . Vessot and Weisen Shen}, journal={IEEE transactions on ultrasonics, ferroelectrics, and frequency control}, year={1987}, volume={34 6}, pages={622-8} }