Experimental examination of the enhancement of gyrotron efficiencies by use of profiled magnetic fields

It is pointed out that the gyrotron has become a very promising source for high-power millimeter-wave radiation. For cases involving the use of magnetic profiling, perpendicular efficiencies of 85 percent have been calculated by Chu et al. (1980). Of the proposed methods which utilize an approach involving a profiling of the magnetic field, a procedure based on the employment of a linear ramp has great promise with respect to ease of implementation and the achievable efficiency level. This procedure is further investigated. Attention is given to experiments performed at a frequency of 35 GHz and a calculation of the electronic efficiency. It is found that magnetic field profiling can enhance the efficiency of a gyrotron by a factor of 1.5-1.9. As a result, an electronic efficiency of 67 percent is demonstrated.