Hydrogen maser uses the transition frequency of hydrogen atom at hyperfine energy level of ground state torealize precise timing. It has excellent frequency stability, especially in medium- and short-term, and lowfrequency drift. It has been used as high-precision frequency standard in engineering fields such as time keeping,navigation, and very long baseline interferometry. Clock transition of hydrogen maser is the transition betweenstates of and . State selection is realized by state selection magnet, throughwhich high energy atoms are converged and low energy atoms are dispersed. In conventional magnet state-selecting system, both atoms of states, which are required for the maser transition, and uselessatoms of states are focused into storage bulb, which places restrictions on the medium- andlong-term frequency stability performance of hydrogen maser. In order to further improve the quality of atomictransition spectral lines and the performance of hydrogen maser, double state-selection beam optical systemwhich is based on the Majorana transition mode is constructed through calculations and simulations. In thiswork, we use Majorana method to invert atomic states. The magnetic field required for Majorana transition isestablished by using two coils with reverse current. The two coils are separated by 71 mm, and the coil axes arealigned with the direction of atomic beam. The other two pairs of transverse Helmholtz coils are separated by22 mm in the center of the state reversal to adjust the zero point of magnetic field, which should coincide withthe atomic beam to ensure a complete reversal of atomic polarity. The state reversal region is surrounded byfour magnetic shields to reduce the influence of stray magnetic fields. Relationship between selected-statemagnetic field gradient and distance of magnetic poles is analyzed by simulation, and trajectories of the atomswith high and low energy under different selected-state magnetic fields are calculated. The utilization andpurity of high energy state atoms entering into bulb atoms are obtained. The purity of the selected state atoms reaches 99% and the utilization rate is 58%. This is ideal for engineeringapplications. It effectively enhances the proportion of state atoms entering into the atomicstorage bulb and ensures the utilization of atoms. We verify the state-selection beam optical systemexperimentally. By turning on double state-selection system the maser signal can be enhanced. By adjusting thecoil current of the double state-selection system, the maser signal varies with coil current, which verifies the effectiveness of double state-selection system
