Study On Basic Theory Of Relativistic Traveling Wave Tube Filled With Plasma

Relativistic traveling wave tube (RTWT) is an important high power microwave device which has been well developed in the past twenty years. The application mechanism is the interaction of a slow space charge wave, propagating in an electron beam, with an electromagnetic wave supported by a slow wave structure and that the high frequency signal is amplified. The RTWT has a lot of applications, such as the cyclotron resonance heating of fusion plasmas, drivers for new-generation high-energy electron accelerators and the phased array radars. Recently, it has been found experimentally that injected plasma into the RTWT may enhanced the interaction efficiency and the output power. Plasma filling can also improve the transmission quality of electron beam, even make beam transmission without a guiding magnetic field. All-Russian Electrotechnical Institute(VEI), Moscow, Hughes Research Laboratories and University of Maryland have reported their research achievements in this area. At first their research focused on the backward wave oscillator. Then research of traveling wave tube filled with plasma has been reported. At present, much research activities in this area have been carried out in Institute of High Energy Electronics, University of Electronic Science and Technology of China. In this dissertation, the theoretical studies on plasma-filled high-power microwaves devices in both the corrugated waveguide and helix structure have been carried out. The main works are as below:1. A plasma-filled traveling wave tube with sinusoidally corrugated slow wave structure is driven by a finite thick annular intense relativistic electron beam and the entire system is immersed in a strong longitudinal magnetic field. By means of the linear field theory, the dispersion relation for the traveling wave tube is derived. The dispersion characteristic of the RTWT filled with plasma is analyzed firstly by numerical calculation. The trends of the change for gain, bandwidth and center frequency of the RTWT are discussed in detail in different cases: various densities of plasma, transmission places of electron beam, voltages as well as currents. Some useful results have been obtained on the basis of the discussion. 2. A helix type slow wave structure filled partially with plasma is immersed in a strong longitudinal magnetic field. By means of sheath model, the linear theory is built up. Hybrid modes which are formed at frequencies where the phase velocities ofelectromagnetic wave and electrostatic wave coincide are found. The trend of change for dispersion characteristic, interaction impedance and linear gain is analyzed in different plasma densities by numerical calculation.3. The principle, characteristics as well as structure of the PASOTRON Amplifier have been analyzed. 4. A relativistic electron beam is injected into plasma whose density is lower than the beam's density. The head of the electron beam pushes out the plasma electrons, leaving an ion channel. The ion focusing force is similar to the magnetic field in binding electrons. The dispersion equation of corrugated waveguide filled with plasma is derived. For TM01 mode, the influence of the gain and bandwidth of relativistic traveling wave tube amplifier affected by geometry parameters of slow-wave structure, such as periods, depth of ripple and average radius of waveguide, are analyzed by numerical calculation. All these are very helpful for designing RTWT.5. The dispersion characteristics of the low frequency plasma modes are analyzed by means of the theory of the smooth walled cylindrical waveguide and the corrugated wall waveguide filled with plasma. Both uniform plasma and infinitely thin annular plasma filling have been discussed respectively. It is found that the dispersion relation without electron beam satisfies exactly the Floquet theorem and the frequency of electromagnetic wave couldn't be confined by plasma oscillation frequency in a corrugated wall waveguide filled with an infinitely thin annular plasma like it was in a completely plasma fi...