Study On Two-Beam Terahertz Radiation Source

In order to develop the high power Terahertz radiation source, the electron beam-wave interactions in a plasma waveguide immersed in a finite magnetic field are studied. And the coaxial gyrotron with two electron beams (CGTB) is proposed and investigated. The results of numerical calculations and PIC simulation show that CGTB has some distinguished advantages: mode competition is improved; output power is enhanced and it is able to obtain dual frequencies radiation, etc.1. The theoretical study on the electron beam-wave interactions in a plasma waveguide immersed in a finite magnetic field is given in the chapter II, in which both the plasma and the electron beam are considered as special media and the surface current density due to the ripple of the plasma/beam is also calculated. According to this approach, the dispersion figure of an electron beam is obtained; the beam-wave interactions in plasma Cherenkov maser and the two-beam instability in a waveguide filled with magnetized plasma have been studied in detail. The results show that this approach is more accurate and can provide more information. In addition, the two-beam instability in a waveguide filled with magnetized plasma is found to be able to produce high power Terahertz radiation theoretically.2. The coaxial gyrotron with two electron beams is proposed and investigated by the linear theory of CGTB. The results of the numerical calculations show that CGTB have a better performance in mode competition than the coaxial gyrotron with one beam (CGOB). Besides, the self-consistent nonlinear program is developed on C++ Builder platform, which can deal with two electron beams and the coaxial cavities with corrugated inner conductor. The results of calculations show the beam-wave interaction efficiency of CGTB can reach the same value as that of CGOB.3. The dual frequency operation (DFO) of CGTB has been investigated. In such an operation, one beam works at the first harmonic while another at l^th harmonic. According to this principle, a CGTB operation on the first harmonic (10GHz), the second harmonic (20GHz) is designed. The results of the numerical calculations and PIC (MAGIC) simulation show that CGTB can obtain high output power at two different frequencies simultaneously. 4. As a preparation for CGTB experiment, the author designs a 0.22THz, TE03 mode gyrotron. The testing results show that the design approach and technics of gyrotron is practicable. In addition the design of a 0.11THz/0.22THz CGTB has been carried out.