Filling Factor and Isolator Performance of the Traveling-Wave Maser

In order to make a large gain and simultaneously large instantaneous bandwidth traveling-wave maser (TWM), it is necessary to orient the * This work was supported in part by the IT. S. Army Signal Corps under Contract No. DA 36-039-SC-89169. 1005 1006 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , MAY 1964 active material so that the susceptibility tensor has a maximum interaction with the RF magnetic field of the slow-wave structure. Quantitatively this is expressed as a filling factor, F, where: 1 F = FVFP. (1)