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