Yuan Xuesong

Theoretical research on electron beam modulation in a field-emission cold cathode electron gun

In order to develop miniaturized and integrated electron vacuum devices, the electron beam modulation in a field-emission (FE) electron gun based on carbon nanotubes is researched. By feeding a high-frequency field between the cathode and the anode, the steady FE electron beam can be modulated in the electron gun. The optimal structure of the electron gun is discovered using 3D electromagnetism simulation software, and the FE electron gun is simulated by PIC simulation software. The results show that a broadband (74–114 GHz) modulation can be achieved by the electron gun with a rhombus channel, and the modulation amplitude of the beam current increases with the increases in the input power and the electrostatic field.

Cavity design and linear analysis of 225 GHz frequency-quadrupling gyroklystron

This paper considers the frequency-quadrupling three-cavity gyroklystrons with successive frequency-doubling in each cavity. The cavities of 225 GHz frequency-quadrupling gyroklystron are designed with the scattering matrices method and the possible operating mode are discussed. With the point-gap theory, the starting currents of the possible operating modes and the potential parasitic modes in the output cavity are calculated. The optimal operating mode is proposed under consideration of the mode competition and the power capacity of the cavity.

The Study of Coaxial Gyrotron with Two Beams

Results of the theoretical analysis and computer simulations for the coaxial gyrotron with two electron beams (CGTB) are given. It is shown that CGTB has a number of advantages, the output power can be doubled and the mode competition can be significantly improved, the CGTB can also operates simultaneously at two modes with different cyclotron harmonics.

Two-Beam Instability for THz Radiation Source

Theoretical study and digital calculations on the two beams instability in a cylindrical waveguide by a finite axial magnetic field for THz radiation source have been given in the paper. In our approach the electron beams are considered the moving non-neutralized plasma and the surface current due to the ripple of electron beams are taken into consideration in the analysis of beam-wave interactions. With the boundary conditions, the dispersion equation was obtained and solved numerically. The results show that under certain conditions, THz radiation may be achieved.

Vavilov-Cherenkov radiation in a Photonic Crystal

Theoretical study and computer simulation on the Vavilov-Cherenkov radiation (VCR) in one dimensional (1D) and two dimensional (2D) photonic crystals are given in the paper. A variety of interesting and important behaviors for the VCR in a 2D photonic crystal have been revealed previously, such as the backward VCR may occur when the electron energy is lower than the threshold, etc.(Chiyan Luo, 2003). Some new important features of the VCR in photonic crystals have been observed and the physical mechanism is studied as well. The possible applications of the VCR in crystal are discussed.

Theoretical study on the two electron-beam instability in a plasma waveguide

In relativistic plasma electronics, both theoretical and experimental studies indicate that the operating frequency of the mechanism of electron beam coupled with a TG mode wave in plasma filled waveguide can not be higher than either the plasma frequency or the beam plasma frequency. However, our recent investigation on the two stream instability (TSI) shows that the operating frequency may be much higher than plasma frequency or the beam plasma frequency.