Theoretical Study of a Plasma-Filled Relativistic Cerenkov Generator With Coaxial Slow-Wave Structure
The linear and nonlinear theory of a plasma-filled relativistic Cherenkov generator with coaxial slow-wave structure (SWS) is developed. Linear analysis includes the space-charge limiting current, dispersion relations, dispersion curves, and coupling impedance. In nonlinear theory, the electron beam space-charge effect, nonsynchronous interaction, and complex reflection coefficients of the electromagnetic wave at the boundaries of the SWS are taken into account. With the assumption of quasi steady state, the self-consistent equations are numerically calculated using the fourth-order Runge-Kutta method. The effects of the relative phase between inner and outer corrugations, phase and amplitude of the complex reflection coefficient at the boundaries of the SWS, and plasma density on device efficiency are discussed. Efficiencies of up to 37% without plasma and about 50% with plasma density of np = 3-7 times 1011 cm-3 are obtained.
An X-Band Dual-Frequency Coaxial Relativistic Backward-Wave Oscillator
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.
Time behavior of gas pressure and PD activity in insulation cavities under AC voltage
In the framework of developing defect-based life models (i.e. the life model of partial discharge-induced damage growth from a micro-void in polymer matrix), ageing tests were performed on PE layered specimens with artificial cavities under constant gas pressure and constant gas volume conditions, respectively. Time behavior of the discharge repetition rate and amplitude were recorded and compared under these two conditions. Results show that pressure variation has little influence on PD activities at constant gas volume. Under constant gas pressure, the evolution of gas volume has similar characteristic to the product of discharge amplitude and repetition rate.