An X-band dual-frequency coaxial relativistic backward-wave oscillator (CRBWO) with sectioned slow-wave structures (SWSs) is presented and investigated in this paper. Through theoretical and numerical analysis and particle-in-cell (PIC) simulation, a combination generation of two stationary single-frequency regimes is selected as the operation regime of the two-section CRBWO, and a better understanding of the high-frequency characteristics of the system, including the unstable beam-wave interaction regions of each section and the operation mode of each section, is obtained. The PIC simulation results indicate that, with an electron beam of 500 kV and 8.7 kA guided by an axial magnetic field of 0.82 T, average power of 700 MW with power conversion efficiency up to 16.1% is obtained, and the two dominant frequencies are 10.06 and 10.49 GHz, respectively. Theoretical analysis indicates that the operation modes of the two sections are TM01 modes.

An X-Band Dual-Frequency Coaxial Relativistic Backward-Wave Oscillator

We have studied the possibility of controlling the radiation spectrum of a high-power relativistic backward wave tube (BWT) by varying the period of its delay system. For a BWT comprising several sections with different corrugation periods, two-and three-mode generation regimes with commensurate amplitudes of spectral components have been found, the separation of which can be controlled by changing the corrugation period. It is shown that, for a sufficiently large detuning, such a configuration of the interaction space makes possible the generation of noiselike chaotic signals with separated or overlapping spectra. In the latter case, the width of the radiation spectrum is almost twice that of a regular BWT of the same length.

On the synthesis of radiation spectrum in a sectioned relativistic backward wave tube

Two types of relativistic backward wave oscillators (RBWOs) used to produce dual-band microwaves are proposed and investigated by use of the particle-in-cell(PIC) simulation code KARAT [V. P. Tarakanov, User’s Manual for Code Karat (Berkeley Research Associates, Springfield, VA, 1992)]. The first type of RBWO, for generation of C -band and X -band microwaves, is designed based on a single beam and a sectioned structure. With an electron beam of 650 keV and 5.0 kA guided by a magnetic field of 2.0 T, an average power of 380 MW with a total power conversion efficiency of 11.7% is obtained and the frequencies are 5.48 and 9.60 GHz, respectively. By changing the distance between the two sections, single-band oscillations are realized with higher power conversion efficiency than that of the dual-band oscillation. The second type, based on a coaxial structure and dual parallel annular beams, is a dual-band RBWO designed with separated beam-wave interaction regions for generation of C -band and X -band microwaves. With a dual beam of 650 keV and 11.8 kA (the outer beam current is 6.4 kA and inner beam current is 5.4 kA) guided by a magnetic field of 2.0 T, an output power of 1400 MW with a total power conversion efficiency of 18.3% is generated and the frequencies are 4.60 and 8.40 GHz, respectively. PIC simulations demonstrate that the two beam-wave interaction regions operate independently. The two types of dual-band RBWO are also compared and analyzed.

Dual-band relativistic backward wave oscillators based on a single beam and dual beams

An X-band dual-frequency coaxial relativistic backward-wave oscillator with a modulating resonant reflector is presented and investigated in this paper. Through a theoretical study, numerical analysis and particle-in-cell (PIC) simulation, the stationary single-frequency regime is selected as the operation regime, and the high-frequency characteristics of the system, including the unstable beam?wave interaction regions and operation mode of each section, are obtained. The PIC simulation results indicate that an average power of 1.07?GW with a power conversion efficiency of 24.2% is obtained with an electron beam of 520?kV and 8.5?kA guided by an axial magnetic field of 2.4?T, and the two dominant frequencies are 9.43 and 10.30?GHz, respectively. Furthermore, a periodic-like change in the smaller dominant frequency with a frequency agility bandwidth of about 0.40?GHz is acquired.

A dual-frequency coaxial relativistic backward-wave oscillator with a modulating resonant reflector

A dual-band high-efficiency coaxial relativistic backward wave oscillator (CRBWO) with asymmetric resonant reflector is designed and presented in this paper. Improved sectioned coaxial slow wave structure (SWS) with stepwise variation of coupling impedance and phase velocity is employed, and the performance of the dual-band CRBWO is investigated by use of a 2.5-D particle-in-cell (PIC) simulation code. When the diode voltage is 510 kV and beam current is 9.03 kA, an average microwave power of 1.0 GW with power conversion efficiency of 21.7% is obtained. Synchronously radiating dual-band frequencies of 8.1 GHz and 9.9 GHz are obtained, corresponding to C-band and X-band, respectively. A more clear and stable beating radiation microwave power with beating frequency of 1.8 GHz is acquired.

Design of a high-efficiency dual-band coaxial relativistic backward wave oscillator with variable coupling impedance and phase velocity

A Cherenkov oscillator operating simultaneously at two different wave bands (3cm and 8mm) is described in this paper. Experimental results from the oscillator are reported. The measured output power is 10 MW at 3cm wave band, and 1MW at 8mm wave band. The operating modes for BWO and R-orotion are E01 and E13, respectively.

Jiayi Li

Papers

A Cherenkov oscillator operating at two different wave bands