Search

This paper is intended to propose the numerical methodology in optimizing the cusp gun for a 70-kV, 1-A W-band gyrotron traveling wave amplifier working at the second-harmonic TE21 mode. Two numerical methods using the simulated annealing algorithm (SAA) and genetic algorithm (GA) are adopted to perform the gun optimization. Classical electron optics software EGUN is employed to compute the beam trajectories. Maintaining the velocity ratio around 1.6, the axial velocity spreads optimized by SAA and GA are 1.44% and 0.33%, respectively, which means a great improvement compared with the manually optimized value of 2.78%. An analysis of the impact of parametric fluctuation on beam quality indicates that this cusp gun can be stably operated within a reasonable parameter scope. This paper will help to enhance the efficiency of electron gun design for gyrotron devices. [ABSTRACT FROM AUTHOR]

To accurately measure the performance of dielectric loaded circuits for gyrotron traveling wave tubes, a novel topological structure to generate the TE21○ or TE01○ (superscript represents circular waveguide) mode is proposed and verified in this paper. The topology is constituted by an overmoded TE10□ to TE20□ (superscript represents rectangular waveguide) mode converter with multiple matching steps and a taper from TE20□ to TE21○ or TE01○ mode. This topology allows the TE21○ or TE01○ mode to be excited by changing the taper dimensions. Simulation results reveal that the TE21○ and TE01○ mode converters, respectively, have a 1-dB bandwidth of 12.8 and 9.3 GHz with an excellent performance. Converters for the back-to-back millimeter-wave measurements were fabricated with computerized numerical control and wire cutting techniques. Vector network analyzer measurements are in good agreement with the simulations. [ABSTRACT FROM PUBLISHER]

In this paper, a novel triode-type magnetron injection gun (MIG) with three emitters designed for gyrotron traveling wave amplifiers has been presented. This MIG can be operated in Ku/Ka/Q single band or Ku-Ka/Ka-Q dual band. The optimization of the MIG is accomplished by a multiobjective genetic algorithm method. It is anticipated that this MIG possesses an axial velocity spread of <5% in all the operating frequency bands. The results of sensitivity study show that this MIG can work stably within reasonable parametric windows. Velocity spreads considering cathode surface roughness and initial thermal temperature are analyzed. Cathode configuration with heat insulation chambers is introduced to cut off the thermal flow among the emitters. Thermal analysis has been performed. [ABSTRACT FROM AUTHOR]

In order to enhance the efficiency of confocal gyrotron traveling-wave tubes (gyro-TWTs), this paper is intended to present a novel triode-type magnetron injection gun for a 140-GHz 2-kW confocal gyro-TWT. This novel gun, which has a pair of sectorial emitters, is expected to obtain an axial velocity spread of 7.83% and a velocity ratio of 1.01 with an anode voltage of 35 kV and a beam current of 2.4 A. The design procedure has been given in detail. Computer simulations have been carried out using 3-D electromagnetic code computer simulation technology particle tracing. The sensitivity analysis has been performed to study the parametric dependence of modulating anode voltage, accelerating anode voltage, and cathode magnetic field on beam qualities. Results show that this novel gun can be operated stably within a certain parametric scope. [ABSTRACT FROM AUTHOR]

The effects of a small misalignment of the inner rod in a corrugated coaxial-gyrotron on eigenvalue, resonant frequency, and electronic efficiency, and so forth, are presented. As a practical application, with the electronic velocity spread and cavity wall resistivity being taken into account, the beam–wave interaction of a 170 GHz megawatt corrugated coaxial-gyrotron operating with TE 31,12 mode has been investigated. The results show that the eigenvalue increases slightly when the ratio of misalignment to outer radius D/R increases in the case of small ratio of outer to inner radius C= R/R_{\rm {in}} , but is uniform in the case of large ratio of C$ . The electronic efficiency decrease slightly when $D/R$ increases within the range of 0–0.01. If $D/R$ increases to 0.02, the efficiency decreases seriously to only about 5%. For both cold cavity and hot cavity, the resonator frequency increases with $D/R$ increasing. [ABSTRACT FROM AUTHOR]

This paper is intended to present the optimal design of a triode type magnetron injection gun (MIG) for a 300 kW, 30 A gyrotron traveling wave tube (gyro-TWT), which is operated at Q band fundamental TE 01 mode. Based on the analysis of velocity ratio (VR) distribution along the emission strip (ES), a further optimization of cathode geometry on the basis of a preliminary optimized gun is performed, and a new cathode structure is proposed. Compared with initial optimal parameters, the new structure demonstrates a decline of transverse velocity spread (TVS) from 3.66% to 0.57% and longitudinal velocity spread (LVS) from 4.11% to 0.72%, while VR is maintained at 1.05. The achieved overall LVS reaches as low as 3.44% when considering cathode surface roughness and thermal temperature effect. The sensitivity study has been carried out by changing the gun parameters like anode voltage, beam current, and cathode magnetic field to ensure the practical operation stability. [ABSTRACT FROM AUTHOR]

The effects of a tiny misalignment of the inner rod in a coaxial-gyrotron on the eigenvalue, quality factor Q , resonant frequency, and electronic efficiency are investigated. As a practical application, with the electronic velocity spread and cavity wall resistivity being taken into account, the beam–wave interaction of a 170 GHz MW coaxial-gyrotron operating with TE 31,12 mode has been studied. The results show that the eigenvalue of the operating mode decreases slightly when the ratio of misalignment to outer radius D / R increases for the case of smaller values of the ratio of outer to inner radius C = R / R in , but is unchanged with the increasing value of D / R for the case of large ratio of C . The electronic efficiency decrease slightly when D / R increases within the range of 0–0.015. However it decreases at a faster rate when D / R is larger than 0.015. If D / R increases to 0.024, the efficiency decreases sharply to only about 2.2%. For both cold and hot cavity, the resonant frequency decreases slightly with D / R increasing. [ABSTRACT FROM AUTHOR]