Liu Shenggang

Surface plasmon wave propagation along single metal wire

Recently, the single metal wire (SW) has become attractive for its potential applications in the terahertz and higher frequency range. However, as the most simple and typical surface plasmon polariton (SPP) transmission line, its study seems far from enough. Many important transmission behaviours have not been explained satisfactorily from the viewpoint of physics. In this paper, making use of the modified Drude model (MDM) based on the Sommerfeld theory, the transmission behaviours of SPPs along SW are systemically investigated theoretically. Some important physical phenomena such as the mode transformation, the lifetime of the radiative mode and the resonance frequency are revealed, and their mechanisms are explored. The results obtained in the paper will facilitate a general understanding of the features and the physical essence of the SPP transmission, not only for SW itself but also for other SPP transmission lines.

The kinetic theory of the electron cyclotron resonance maser with space charge effect taken into consideration

The kinetic theory of the electron cyclotron resonance maser is given in this paper with the space charge effect and non-resonance cyclotron harmonics taken into consideration. The dispersion equations have been calculated using a digital computer and the influence of these factors are discussed in detail.

Theory of harmonic gyrotron with multiconductors structure

A novel gyrotron RF structure operating at a substantially reduced magnetic field is proposed. The cavity consists of multiconductors distributed around a circle, with or without an inner conductor. The multiconductor, which is a slotted cylindrical metal shell, has the effect of creating a strong harmonic field near the electron orbits and, as a result, greatly reducing the beam voltage for harmonic operation. The efficiency of the field-electron interaction is examined numerically. For fifth and sixth harmonic of the electron cyclotron frequency, a maximum overall efficiency of 15·2% and 14·2%, respectively, has been calculated

Theory of wave propagation along corrugated waveguide filled with plasmas immersed in an axial magnetic field

Analytical theory of wave propagation along a corrugated waveguide filled with plasmas immersed in a finite axial magnetic field is presented in this paper. Preliminary numerical calculations are also done, showing that the intensity of magnetic field has considerable influence on the dispersive characteristics of wave propagation and the properties of such devices.

Basic theoretical formulation of plasma microwave electronics. II. Kinetic theory of electron beam-wave interactions

For pt.I see ibid., vol.28, no.6, p.2135-51 (2000) Building upon the theoretical foundations presented in Part I of this paper, the kinetic theory of electron-beam-wave interactions in a magnetized plasma-filled waveguide (MPW) is presented in this second part. This kinetic theory treatment is more generally applicable to cases of less-intense electron-beams (Montgomery and Tidman, 1964). The dispersion relations for longitudinal and transverse interactions, in both smooth and corrugated waveguides, are all derived by using kinetic theory to model the e-beam dynamics. This includes kinetic theory treatments of the plasma filled electron cyclotron resonance maser (ECRM) and a combination of Cherenkov-cyclotron resonance phenomena. It is important to note that in an MPW, transverse interactions (e.g., ECRM interactions) are always coupled with longitudinal interactions. Using the kinetic treatment is essential for studying the ECRM because its energy conversion mechanism is based on azimuthal phase bunching and finite Larmor radius effects. The dispersion relation that we derive shows that the presence of a plasma-fill tends to increase the growth rate of the waveguide mode ECRM instability.

Third-harmonic complex cavity gyrotron self-consistent nonlinear analysis

Starting from general transmission line equations with an electron beam source, a self-consistent nonlinear theoretical model for a complex cavity gyrotron with gradual transitions is presented in this paper. The model accounts for mode coupling in the transition region of the complex cavity. The interaction between the electron beam and H/sub 61/-H/sub 62/ RF field in the complex cavity for a third-harmonic gyrotron is simulated; many calculations are carried out under different cavity dimensions and electron beam parameters.

35 GHz third-harmonic gyrotron with a permanent magnet system

A systematic theoretical and experimental study on 35 GHz 45 kV third-harmonic gyrotron with a permanent magnet system is presented in this paper. A complex cavity with gradual transition, and a diode magnetron injection electron gun (MIG) are employed in the gyrotron. The permanent magnet system provided the axial magnetic field of about 4.5 kG in the cavity region. The Ka band third-harmonic gyrotron with a permanent magnet system has been designed, constructed and tested. A peak output power of 147.3 kW was obtained at a beam voltage of 45 kV with beam current of 32.2 A, corresponding to an efficiency of 10.2%.

Gyrotron with quasi-optical cavity of special configuration†

Abstract A quasi-optical cavity of special configuration suitable for use in a high-power gyrotron operating at short millimetre and submillimetre wavelength has been developed. A gyrotron using this new type of cavity is under development. Both the linear and non-linear analyses are worked out. Digital calculation predicts efficiency of 37% at V 0 = 50 kV.

Static strength of gold compressed up to 127 GPa

Gold powder is compressed non-hydrostatically up to 127 GPa in a diamond anvil cell (DAC), and its angle dispersive X-ray diffraction patterns are recorded. The compressive strength of gold is investigated in a framework of the lattice strain theory by the line shift analysis. The result shows that the compressive strength of gold increases continuously with the pressure up to 106 GPa and reaches 2.8 GPa at the highest experimental pressure (127 GPa) achieved in our study. This result is in good agreement with our previous experimental result in a relevant pressure range. The compressive strength of gold may be the major source of the error in the equation-of-state measurement in various pressure environments.

Dielectric effect on the rf characteristics of a helical groove travelling wave tube

A new type of partial-dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analysed. The results show that the dispersion of the helical groove circuit is weakened, the phase velocity is reduced and the position of the maximum Ez is moved from the mouth to the inside of the groove after partially filling the dielectric materials in the helical groove SWS. Therefore, the dielectric-loaded helical groove SWS is suitable for a multi-beam TWT with broad band and high gain.