Experimental studies of overmoded relativistic backward-wave oscillators

Abstract

Internal field-emission breakdown in the electrodynamic structures of high-power microwave (HPM) devices can seriously limit the device's output power and pulse duration. Increasing the diameter of the electrodynamic structure to several times an electromagnetic wavelength can reduce these internal fields to below critical breakdown levels, but may introduce mode competition as an unwanted side effect. This paper presents the design and results of experiments with overmoded (D= 3), sinusoidally corrugated backward-wave oscillators (BWO's) that successfully produced TM 01 , high-power microwave radiation in the frequency range of 5.2-5.7 GHz. Overmoded BWO's reproducibly generated 200 MW of peak power with corresponding efficiencies of 4%. Pulse shortening was not observed in any of the experiments. The radiation generated by the devices was highly coherent (typically, 1f=f < 0:5%) and corresponded to a fundamental TM 01-mode interaction. The experimental results were compared with calculations made with recently developed nonlinear models; the measured data are shown to agree favorably with theory. The results of the experiments and modeling demonstrate that overmoded electrodynamic structures can be used to decrease internal electric field stresses while avoiding multimode generation and maintaining good spectral purity.

A repetitive 0.14 THz relativistic surface wave oscillator

“…To overcome these problems, the overmoded structure is the best choice, though it was introduced for increasing the maximum handling power in microwave devices at first. [12][13][14] So an overmoded RSWO, one of typical Cerenkov devices, is adopted to generate 0.14 THz high power radiation in our design. The 0.14 THz RSWO with key structural parameters denoted is schematically shown in Fig.…”

Experiment on the plasma-loaded backward-wave oscillator using a gas-loaded foil-less diode

“…Many authors [1][2][3][4][5][6][7][8][9][10][11][12] have focused their attention on this device for more efficient operation at high-power levels, and important results have been obtained both experimentally and theoretically. In order to further enhance the output power of microwave and the conversion efficiency of electron beam to microwave radiation, some scientists [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] have introduced background plasmas into the BWOs, and both theoretical and experimental results have demonstrated that the background plasmas improve the beam-waveguide interaction dramatically.…”

Simultaneous operation of X band gigawatt level high power microwaves

“…The oversized approach has been successfully used to increase the power-handling capacities of slow-wave HPM devices. Important examples of overmoded devices are the multi-wave Cerenkov generator (MWCG) developed by Bugaev et al (1990a), the relativistic diffraction generator (RDG) developed by Bugaev et al (1990b), the relativistic backward-wave oscillator (RBWO) developed by Abe et al (1998), and the surface-wave microwave oscillator developed by Vlasov et al (2000). Although significant improvements have been achieved by using overmoded structures to reduce the internal reversed electric fields in HPM devices, there are still other issues that need to be investigated.…”