Efficient generation of multi-gigawatt power by an X-band dual-mode relativistic backward wave oscillator operating at low magnetic field

Abstract

An X-band dual-mode relativistic backward wave oscillator (RBWO) operating at low magnetic field is presented in this paper. Three new design principles are introduced in the device. First, the electron beam interacts with TM01 mode and TM02 mode simultaneously, rather than with a fixed single mode. Second, the device outputs with mixed modes, rather than with a pure mode. Third, an internal reflector inserted into the annular cathode, rather than a long resonant reflector before the slow-wave structure, is adopted to reflect part of the backward wave. Accordingly, the beam–wave interaction efficiency is increased significantly and the whole device is very compact. The particle in cell simulation results reveal that at a magnetic field of 0.64 T, the output microwave power is 4.8 GW and the conversion efficiency is up to 44%. In the experiment, at a guiding magnetic field of 0.66 T, a microwave pulse with power of 4.6 GW, frequency of 9.96 GHz, pulse duration of 42 ns, and efficiency of 42% was generated when the diode voltage was 880 kV and beam current was 12.5 kA, which agree well with the simulation results. Furthermore, as the diode voltage was 1.17 MV, a highest microwave power of 7.6 GW was achieved. This is a record of high efficiency and high power of microwave generation in an X-band RBWO operating at low magnetic field.

Experimental research based on a C-band compact transit-time oscillator with a novel diode loading an embedded soft magnetic material and shielding structure

“…In recent years, there have been many research reports in this area. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] A transit-time oscillator (TTO) is a type of HPM source that has the potential to be miniaturized and compact due to its simple structure, which can work efficiently with a low external guiding magnetic field. This kind of device has attracted increasing interest from researchers.…”

Harmonic generation in magnetized plasma for electromagnetic wave propagating parallel to external magnetic field

“…While high-power lasers have already been available for a long time, the production of high-power microwave (HPM) sources is more recent [21][22][23]. In a recent study [23,24], an HPM pulsed source of up to 4.6 GW and of frequency 9.96 GHz has been achieved in experiments. These HPM sources have stimulated interest in the study of nonlinear effects in microwave plasma interaction.…”

Experimental study on the influence of grain boundary on breakdown in relativistic backward wave oscillator

“…Since the first HPM experiment based on a RBWO was conducted in 1970, the output power and single pulse energy of this device have both increased tremendously [7][8][9][10][11]. The X-band microwave output with a power of 7.6 GW has been experimentally achieved by proposing a klystron-like RBWO, while severe pulse shortening has occurred under this microwave power [12]. The phenomenon of pulse shortening is a critical bottleneck that prevents the achievement of higher output power and longer pulse width by RBWOs [13][14][15].…”