Yong Yin

Simulation and Experiments of a

This paper presents the first experimental results of an extended interaction oscillator (EIO) based on a pseudospark-sourced electron beam, which produced a peak output power over 38 W at W-band. The advantages of the newly developed device are: 1) transport of the electron beam by the positive-ion focusing channel without the need of an external magnetic field and 2) high interaction impedance and high gain per unit length of the EIO circuit. The experimental results agree well with the 3-D particle-in-cell simulations.

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The design and simulation of a G-band extended interaction oscillator (EIO) driven by a pseudospark-sourced electron beam is presented. The characteristic of the EIO and the pseudospark-based electron beam were studied to enhance the performance of the newly proposed device. The beam-wave interaction of the EIO can be optimized by choosing a suitable pseudospark discharging voltage and by widening the operating voltage region of the EIO circuit. Simulation results show that a peak power of over 240u2009W can be achieved at G-band using a pseudospark discharge voltage of 41u2009kV.

-Band Extended Interaction Oscillator Based on a Pseudospark-Sourced Electron Beam

A new kind of coaxial vircator with a three-mirror quasi-optical resonate cavity is proposed and studied in this paper. Theoretical study and particle-in-cell (PIC) simulation are both included. Through two-and-a-half-dimensional PIC code MAGIC, using an input voltage pulse with peak value of 600 kV the average voltage obtained on the diode is 460 kV and the diode current is 50 kA, the instantaneous output power with peak value over 4 GW and the average power 2 GW are obtained with frequency 7.0 GHz. The beam-wave conversion efficiency is reaching 8.7%.

Preliminary design and optimization of a G-band extended interaction oscillator based on a pseudospark-sourced electron beam

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.

Study of a coaxial vircator with a three-mirror quasi-optical resonant cavity

Smith-Purcell (SP) radiation has been widely used for the generation of radiation from microwave to optical frequencies, and it has recently become an attractive candidate for a Terahertz (THz) radiation source. Superradiant SP radiation has sharp angular and spectral distributions due to the bunching of the electron beams, and a three-mirror quasi-optical cavity (TMQOC) which has selectivity at both angles and frequency has been designed to enhance this process. The radiation power over 700 W/m at the 99.4 GHz are obtained through using a 45-keV 4-A/m beam skip over a metal grating with period, width, and depth are 1.6, 1.0, and 0.8 mm, respectively. This results show that the TMQOC can greatly enhance the superradiant SP radiation, and one may utilize this effect to design a compact, tunable, and powerful THz radiation source working at room temperature.

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

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.

Enhanced Superradiant Smith–Purcell Radiation in a Three-Mirror Quasi-Optical Cavity

Extended interaction oscillator (EIO) operation in the terahertz range puts greater demand on the current density and brightness of an electron beam. The pseudospark (PS)-sourced electron beam is a good candidate for driving such high frequency EIOs as it has a very high combined beam current density and brightness. However, the PS-sourced electron beam can have an inherent velocity spread unless some form of post acceleration is used. Before a new EIO device in the Y-band (220 GHz–325 GHz) based on a PS-sourced electron beam can be realized, it is first necessary to analyze the influence of the beam velocity spread on performance. This paper presents the numerical studies of the EIO performance with the inclusion of the beam velocity spread. It was found that the Y-band EIO circuit can operate in a relatively wide velocity spread range when a high beam current density is used. For an electron beam current density of 1u2009kA/cm2, the output power is not less than 0.9 times of the power obtained with an elect...

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

ABSTRACT The relationship between surface loss and field flatness in extended interaction device (EID) has been studied. The field flatness can influence the surface loss in the circuit and hence the efficiency of the device without changing the operation mode. A W-band nine-slot extended interaction circuit operating in the 2π mode has been used in this article. As an oscillator, the nine-slot interaction circuit has different surface loss regions when the field flatness is different. In the study of EID, the operation point is mainly determined by the slow wave structure, but the field flatness should also be studied carefully for it influences the surface loss in the circuit and hence the efficiency of the device.

The effect of velocity spread of pseudospark-sourced electron beam to Y-band extended interaction oscillator

An innovative wire-wrap structure was applied as the slow-wave circuit for a backward wave oscillator (BWO) operating in terahertz (THz) band. The construction of the device features a periodic fine copper wire, a rectangular ridged waveguide, and a rectangular cavity in the upper cover plate. Based on the novel structure, the performance of the device presented by dispersion characteristic, coupling impedance, and S-parameters was analyzed and optimized in the design process. The electron beam parameters with an outer diameter of 0.26 mm have relatively low accelerating voltage around 1.2 kV and beam current of 0.05 A (the current density is 94 A/cm2). Under such conditions, numerical simulation results predict that the novel oscillator is capable of achieving the output peak power in excess of 154 mW and a tunable 3-dB bandwidth over 24 GHz in the range from 324 to 348 GHz. In addition, the machining and assembling methods of wire-wrap structure are another original invention for the physical processing of THz BWO.

Study of the relation between the surface loss and the field flatness in the EID

The circuit suitable for the hollow electron beam (HEB) interaction was formed by parallel connecting of the sheet beam extended interaction klystron circuit at the angular direction. The analysis of this newly developed circuit shows it can interacts with the distributed HEB. To demonstrate this capability, a W-band extended interaction oscillator (EIO) with distributed HEB has been designed. A DC distributed HEB with 27 keV energy and 8A current was injected into the interaction circuit, simulations with a 3-D Particle-in-cell (PIC) code predict an output power up to 6.6 kW at 99.7 GHz was obtained.