Shao Hao

A New Reflector Designed for Efficiency Enhancement of CRBWO

A new reflector consisting of the inner and outer conductors is introduced into the coaxial relativistic backward wave oscillator for the first time through optimizing the distribution of the electric field and distance between the reflector and the slow wave structure. The improved reflector can excite the superposition of the axial electric fields to benefit the electron premodulation. The improved reflector is investigated by the particle-in-cell numerical simulation. A result of 43% power efficiency, 1.0-GW power, and 7.3-GHz operation frequency is obtained under the diode voltage 530 kV and current 4.4 kA.

Simulation Studies of a Relativistic Klystron With Strong Input Power

As one of the potential high-power microwave devices on the level of gigawatts, relativistic klystron amplifier (RKA) can be used for power combination to further improve the radiation microwave power. Because of self-excited oscillation of the intense relativistic electron beam, the frequency and phase characteristics of general relativistic klystron devices are independent with the driven microwave pulse. In order to obtain frequency and phase locking, a method of improving the input power is put forward to inhibit these parasitic oscillations. This paper reports a particle-in-cell simulation study of the RKAs characteristics under the condition of strong power feeding. By making use of the 500-keV 6-kA electron beam, the simulation results show that strong input power can inhibit the parasitical oscillations in cavity and modulate the beam very well with only one cavity. About 5.4-kA modulation current and a microwave with power of 1.4 GW, bandwidth of 5%, and efficiency of 50% are obtained. The new amplifier driven by the strong input power proves to be a potential device to attain high amplitude stability, high efficiency, high spectral purity, wide bandwidth, and low level of phase and amplitude noise.

Theoretical investigation of an electron beam propagating through a wide gap cavity

This paper presents a self-consistent nonlinear theory of the current and energy modulations when an electron beam propagates through an inductively-loaded wide gap cavity. The integro-differential equations are obtained to describe the modulation of the beam current and kinetic energy. A relativistic klystron amplifier (RKA) model is introduced, which uses an inductively-loaded wide gap cavity as an input cavity. And a numerical code is developed for the extended model based on the equations, from which some relations about the modulated current and modulated energy are numerically given.

Space-charge limiting current in spherical cathode diodes

The results of the investigation on the space-charge limiting current for a spherical-cathode diode in the non-relativistic situation are presented in this paper. The results show that the current enhancement factor equals the square of E-field enhancement factor on the cathode surface. The generated space-charge limiting current is deduced. In the case of a pin-shaped-cathode diode, the space-charge limiting current is also obtained, indicating that the current is independent of the geometric parameters of the diode. Analyses of the shielding effects and the conditions for generation of the uniform space-charge limiting beam show that, for pin-arrayed cathodes, the distance between pins should be in the range from 1.2D to 1.5D, where D is the distance between the two electrodes.

Growth rate of the Coaxial Slow Wave Structure

The growth rate of the Coaxial Slow Wave Structure is studied through a simple method employing the relativistic Newtons equation, the driving Maxwell equations and the linear assumption of the small signals. In addition, effects of the electron kinetic energy and the beam current on the growth rate are investigated preliminarily.

Design and near field characteristic of high power microwave dual-reflector antenna

The high power microwave (HPM) dual reflector antenna is the important part of HPM transmission and radiation system. The paper is focused on the near field characteristic and the power capacity of the HPM dual reflector antenna. The dual reflector antenna is suitable for HPM radiation and the power capacity of the antenna is giga watts range.

Effect of longitudinal applied magnetic field on the self-pinched critical current in intense electron beam diode

The effect of applied longitudinal magnetic field on the self-pinched critical current in the intense electron beam diode is discussed. The self-pinched critical current is derived and its validity is tested by numerical simulations. The results shows that an applied longitudinal magnetic field tends to increase the self-pinched critical current. Without the effect of anode plasma, the maximal diode current approximately equals the self-pinched critical current with the longitudinal magnetic field applied; when self-pinched occurs, the diode current approaches the self-pinched critical current.

Approximate Relativistic Solutions for One-Dimensional Cylindrical Coaxial Diode

Two approximate analytical relativistic solutions for one-dimensional, space-charge-limited cylindrical coaxial diode are derived and utilized to compose best-fitting approximate solutions. Comparison of the best-fitting solutions with the numerical one demonstrates an error of about 11% for cathode-inside arrangement and 12% in the cathode-outside case for ratios of larger to smaller electrode radius from 1.2 to 10 and a voltage above 0.5 MV up to 5 MV. With these solutions the diode lengths for critical self-magnetic bending and for the condition under which the parapotential model validates are calculated to be longer than 1 cm up to more than 100 cm depending on voltage, radial dimensions and electrode arrangement. The influence of ion flow from the anode on the relativistic electron-only solution is numerically computed, indicating an enhancement factor of total diode current of 1.85 to 4.19 related to voltage, radial dimension and electrode arrangement.