Integrated microwave cavity resonator and magnetic shield for an atomic frequency standard

The subject invention relates to an improved microwave cavity resonator and internal magnetic shield of small design for use with an atomic frequency standard. In an embodiment for an optical-physics package the invention comprises a light source, a cell having a predetermined volume in which atoms are contained capable of undergoing a hyperfine transition within a microwave region of the spectrum and disposed to receive the light from said source, a microwave cavity resonator composed of a ferromagnetic or magnetically equivalent material and having a cavity substantially commensurate in volume with the predetermined cell volume, means for detecting the light transmitted through said cell and producing a detection signal representing the transmission of light therethrough, means for subjecting the cell within said cavity to electromagnetic waves inducing the hyperfine transition of the atoms to increase the absorption of the light, means for applying a magnetic field to the cell to provide a substantial bias field to said cavity, said means for applying said magnetic field being generated within the cavity, and control means responsive to the detection signal for modifying the frequency of said electromagnetic waves so as to steer and maintain their frequency substantially centered on the frequency of the hyperfine transition of said atoms.