PAPER 15 – The Three-Level Solid State Traveling-Wave Maser†*

Broadband very-low-noise microwave amplification can be obtained from solid state maser action in a propagating microwave structure. Such a traveling-wave maser produces unilateral amplification with a high degree of gain stability. The theory of the traveling-wave maser is developed and used to compare the gain, bandwidth and gain stability of the traveling-wave maser with that of the cavity maser. The general requirements for traveling-wave maser slow-wave structures are discussed. Theoretical analysis and experimental results are presented for the comb-in-waveguide slow-wave structure. A traveling-wave maser consisting of a ruby-loaded comb structure was tested. A gain of 23 db at 6 kmc with a bandwidth of 25 mc was obtained. Further performance characteristics of this amplifier and one using gadolinium ethyl sulfate are given. Experimental verification of the low noise temperature of solid state masers was obtained.