Design for a Subcompact Q-Enhanced Active Maser

Abstract

A design is presented for a compact hydrogen maser considerably smaller than those previously developed by this laboratory. The design uses cavity loading to reduce the diameter and length of the microwave cavity to 3 in., and Q-enhancement to achieve maser oscillation. The smaller cavity size leads to commensurate reductions in the size of several other components, particularly the magnetic shields, with the result that the assembled physics package (microwave cavity, vacuum chamber, dissociator, state selector and four nested magnetic shields) will fit within a 5.5-in. by 5.5-in. by 14-in. envelope. Significant improvements have also been made in the size and power consumption of the maser electronics. New, smaller components have allowed a complete microwave front-end (a 1.42-GEz amplifier, an active mixer, an active phase shifter and attenuator, a 5 to 1400-MHz frequency multiplier, several dividers and combiners) and a critical part of the cavity-control electronics to be housed in a 5.5-in. by 5.5-in. by 2-in. package. Further reductions in system size have been made possible by the commercial availability of integratedcircuit number controlled oscillators (NCOs), which have permitted the development of small, efficient frequency synthesizers for the receiver and cavitycontrol system. The maser which will result when all of these components are combined should prove very attractive for applications in which high stability, small package size and low weight are ll critical requirements.