A "C"-band rutile traveling-wave maser

The development of a traveling-wave maser (TWM) with an iron-doped rutile active crystal and a meander line slow-wave circuit is described. This maser exhibited high-quality performance over a frequency range of 5.4 to 5.9 Gc. Iron-doped rutile exhibited a fast recovery time from saturation signals (3.5 ms). Inversion ratios of 10 to 1 were obtained with conventional microwave pumping techniques and a two-pump technique provided ratios of 13 to 1. This maser has been operated with a superconducting magnet.