Research On Back Wave Oscillator Device With Carbon Nanotube Cold Cathode

Carbon nanotube(CNT) which has excellent field emission characteristics can be an ideal cathode material for the field emission devices. In order to develop microwave and millimeter wave electric vacuum radiation source devices with CNTs cold cathode, the field emission characteristic of CNTs cold cathode is researched, and a back wave oscillator device with CNTs cold cathode is designed in this paper. The BWO device can work in frequency range of 8mm band. The main body of research as follows:(1) Field emission characteristic of CNTs cold cathode with a diameter of 4mm is researched and the maximum emission current density of 127mA/cm2 is obtained. Based on the experimental results, field emission simulation model of CNTs cold cathode is established by three-dimensional electromagnetic simulation software. The influence of mesh grid structure on CNTs cold cathode has been analyzed. An optimal size of mesh grid structure is obtained. While the size of mesh grid is selected to d=0.1mm and D=0.4mm, CNTs cold cathode has good emission property and the transparency of electron beam can be 60%.(2) A sheet beam electron gun with CNTs cold cathode is designed. The effects of mesh grid structure, anode voltage and magnetic field on sheet beam electron have been analyzed. Simulation results of the sheet beam electron gun show: when the gun worked on a grid-cathode distance of 0.25 mm, grid voltage of 2.5 kV, anode voltage of 18 kV and a periodic permanent magnetic field, the waist radium of sheet beam electron is 0.35 and the output current density can get to 17.2 A/cm2.(3) Combined with EIGENMODE solution, the dispersion of rectangular double vane slow-wave structure has been deduced. The structure of metal rectangular double vane used for frequency of 8mm band is designed by three-dimensional electromagnetic simulation software.(4) Carbon nanotube cold cathode is used as radiation source in BWO device. The back wave oscillator worked in in frequency range of 8mm band is researched by PIC simulation software. The simulation results show that BWO with CNTs cold cathode produced a back wave of 33.95 GHz, the output power can be 2.35 kW, and the signal efficiency is up to 8.73%.