A 60 GHz, 200 kW CW gyrotron with high output mode purity

Abstract

For the first tlae, a Varlan 60 GHz gyrotron, designed specifically to generate microwaves In a single output aode, has been operated .:'-power levels up to 200 kW CW. High ou .put mode purity is required for the efficient utilization of gyrotrons as high power Microwave sources for electron cyclotron resonance heating (ECRH) In Magnetic fusion plasmas. Using node-speclt'ic directional couplers, Measurements of the output Mode content Indicated that greater than 951 of the microwave output was in the desired TE02 aode, with only snail percentages In the neighboring TE0, and TE03 circular electric aodes.The pure node CW design uses a 2.5-inch diameter collector. The collector has a magnetic field arrangment which capably avoids excessive heating by distributing the 610 kW CW beam over a sufficient collector area. With pure node operation, window temperatures are 10 C to 15 C higher than with eixed Mode operation.