Wenjie Fu

Two-beam magnetron injection guns for coaxial gyrotron with two electron beams

To verify the concept of a coaxial gyrotron with two electron beams (CGTB), an electron gun with two beams is needed. In this paper, two types of two-beam magnetron injection guns are proposed: a normal two-beam magnetron injection gun and a coaxial two-beam magnetron injection gun. The design models and space charge limiting current are given. The simulation results show that both types of guns could fulfill the requirement for a CGTB. Comparisons between the two types of injection guns are discussed.

Design and Experiment of a 220/420-GHz Gyrotron for Nondestructive Evaluation

We report the design and experiment of a 220/420-GHz gyrotron oscillator for nondestructive evaluation which operates at the fundamental near 220 GHz and the second harmonic near 420 GHz of the electron cyclotron resonance frequency. Through optimizing electron gun for both operation modes, the TE26 mode at 423.1 GHz and the TE03 mode at 221 GHz are observed at output powers up to 8 and 6 kW, respectively, by only changing the beam voltage at a magnetic field of 8.2 T. The experimental results are in reasonable agreement with the design and simulation. In addition, the measurements of potential operation modes with peak output power are also presented in this paper.

High harmonic terahertz confocal gyrotron with nonuniform electron beam

The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

Design of a 220-GHz continuous frequency-tunable gyrotron with quasi-optical cavity

The design of a 220 GHz continuous frequency-tunable gyrotron with a three-section tapered quasi-optical cavity is presented. The HE06 mode in quasi-optical cavity is selected as the operating mode. The tuning is achieved by changing the distance between the two mirrors, which ensures continuous variations in eigenfrequencies of the cavity. The PIC simulation results demonstrate the possibility of tuning the oscillation frequency by 8 GHz near 220 GHz (within a frequency band of about 3.6%) with an output power no less than 5 kilowatts.

Experimental results of a 0.42 THz harmonic gyrotron

We report primarily results of a 0.42 THz second harmonic gyrotron. In microsecond pulse length operation at 52kV and 3A, 4.4kW output power have been observed at the TE2,6 mode at 0.423 THz. Modes at fundamental, including the TE0,3 at 0.221 THz and the TE2,3 at 0.216 THz, have output powers up to 20kW.

A high current density plasma cathode electron gun

The design, performance, and characteristics of a plasma cathode electron gun are presented. The plasma cathode is based on a hollow cathode direct current discharge, and the electron beam is accelerated by pulse voltage. By discharging at high gas pressure and operating at low gas pressure, both the maximum accelerating voltage and maximum emitting current could be increased. Utilizing argon, with the accelerating voltage up to 9 kV and gas pressure down to 52 mPa, the gun is able to generate an electron beam of about 4.7 A, and the corresponding emitting current density is about 600 A/cm2.

Design of a magnetron injection gun with low velocity spread for 0.56THz third harmonic gyrotron

In this paper, the design of a double-anode magnetron injection gun for a 0.56THz third harmonic gyrotron is presented. Simulation predicts that a high quality electron beam is generated with parallel velocity spread of 2.19%, perpendicular velocity spread of 1.0%, and velocity pitch spread of 3.18% at α=1.5. The variations of velocity spread due to operation parameters are also presented.

Research on a magnetron injection electron gun based on carbon nanotube cold cathode

In order to develop the microwave and millimeter-wave vacuum electronic radiation source devices with field emission cold cathodes, an electron-optical system based on carbon nanotube cold cathode is investigated in this paper. A magnetron injection electron gun is designed for a 220GHz TE03 mode gyrotron. And the preliminary experiment results of the carbon nanotube cathode show the maximum beam current reach 25mA and the electric field of between cathode and anode is 11.5kV/mm.

Design of a frequency tunable 0.2 THz gyrotron-backward wave oscillator

The preliminary design of a frequency tunable 0.2 THz gyrotron-backward wave oscillator is presented. This gyrotron utilizes reflected structure, and simulations show that, the magnetic tuning bandwidth is over 1GHz, while power is over 1 kW, and the voltage tuning bandwidth is over 1GHz, while power is over 2 kW.

Studies on two-beam magnetron injection gun for coaxial gyrotron with two electron beams

To verify the concept and the theoretical results of coaxial gyrotron with two electron beams (CGTB), the electron gun with two beams is needed. In this paper, two types of two-beam magnetron injection gun (TBMIG): normal two-beam magnetron injection gun (NTBMIG) and coaxial two-beam magnetron injection gun (CTBMIG) are proposed. The simulation results show that both of them can satisfy the requirement of CGTB.