The Experimental Investigation of Continuous Frequency Tuning in Sub-THz Gyrotrons with Short Cavities

In this paper, we present the results of two experiments with sub-terahertz gyrotrons with wide frequency tuning range provided by the use of short cavities. The first experiment is carried out on a 163 GHz gyrotron operating in a TE1,3 mode. In this tube, the excitation of five axial modes provided the frequency tuning band of 2.1 GHz and average output power at high-order modes of 100 W. The second experiment was carried out with the gyrotron designed for second-harmonic 527 GHz operation but switched to the regime of operation at the fundamental cyclotron resonance with TE5,2 mode and 250 GHz frequency. In this gyrotron, the obtained frequency tuning range was 3.8 GHz with output power about of 50 W. Both experiments prove the feasibility of the developed approach and open up new possibilities of gyrotron applications in spectroscopy.