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This article presents the development of a dual-state Ku-band gyrotron traveling-wave tube (gyro-TWT) dual-state curved-profile magnetic injection gun (MIG) generating high-quality electron beams, in which the pitch factor is up to 1.2 and 1.35 for the pulse wave (PW) state and the continuous wave (CW) state, separately. A multiobjective genetic algorithm (MOGA) is applied in the profile optimization. Meanwhile, the parametric sensitivity is also discussed in detail. A periodic dielectric-loaded interaction circuit is adopted to suppress oscillations. Furthermore, thermal analyses of the interaction circuit under different duty cycles are also elaborated. The interaction circuit is analyzed in accordance with the proposed nonlinear self-consistent theory and particle-in-cell (PIC) codes. The results of hot experiments show that the dual-state tube obtains the output power of 150/30 kW corresponding to a saturated gain of 40/41 dB and the maximum efficiency of 25%/21% within the bandwidth of 2.0/1.1 GHz for the PW/CW state, respectively. [ABSTRACT FROM AUTHOR]

The establishment of an automatic hot test platform is one of the important conditions to ensure the safe and stable operation for the gyrotron traveling wave tubes (gyro-TWTs). In order to verify the reliability of the controlling strategies used in the long period hot test of a high peak/average power gyro-TWT, the control process of the cathode-anode beam voltage and current is described by a mathematical model based on a proportional—integral—derivative (PID) controller. The beam voltage is controlled by the high-voltage power supply and the beam current is regulated by the high-voltage power supply and filament heating power. A mathematical model of the PID controller is developed and evaluated by the MATLAB to analyze the performance of the system. The comparison between the experimental and modeling results show that the second-order inertia model with time delay can express the control process of the beam voltage and current well. The PID controlling theory can be used to model the control process of the hot test of a gyro-TWT with digital signal, so that the damage of the immature strategy is prevented. [ABSTRACT FROM AUTHOR]

In this paper, a lossy dielectric-loaded high-gain $X$ -band gyrotron traveling-wave tube (gyro-TWT) which operates at the fundamental circular TE11 mode is designed and analyzed. The designed gyro-TWT has the features of high-gain and megawatt level output power. Lossy dielectric is applied to suppress spurious oscillations and to improve the stability of the gyro-TWT. In addition, the interaction behavior of the electron beam is investigated. In the condition of 4.5 W input power, a peak RF output power of 2.14 MW with a gain of 56.7 dB at 8.4 GHz is predicted, corresponding to the electron beam-wave interaction efficiency of 35.6% at 150 kV, 40 A. The research also obtains stable output power over 1.5 MW in the range of 8–8.4 GHz with 2-W input power and output power over 1.2 MW with 150-W input power in the range of 8.6–9 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a new type input/output (i/o) structure, adopting the multiaperture coupler, for broadband sheet-beam traveling-wave tube was designed and analyzed. This novel coupling structure not only can get a larger electron passway, which will greatly benefit the transmission of the electron beam, without deteriorating electromagnetic transmission characteristics, but also work over an extremely broad bandwidth. The transmission characteristics of this coupling i/o structure are investigated by Ansoft’s high-frequency structure simulator (HFSS). Operating at TE \(_{10}\) mode, the maximum insertion loss and isolation of the i/o structure over 36–52 GHz, which equals to 36.4% bandwidth, are −25 and −20 dB, the transmission coefficient is above −0.3 dB. The results of HFSS were verified by Computer Simulation Technology Microwave Studio. [ABSTRACT FROM PUBLISHER]

The design of a high-power low-velocity-spread space-charge-limited cusp gun is presented. The Lagrangian formulation is used to analyze the velocity spread and beam ripple (orbit center spread). It shows that the two electron orbit off-center mechanisms, the radial velocity and the nonideal cusp magnetic field, can be adjusted to cancel each other. The characteristics of the cusp gun including the cusp magnet are calculated by cosimulation employing the Maxwell2D, Matlab, Egun, and CST-PS codes. The cusp gun is designed to generate a beam of 8 A at 70 kV with a pitch factor from 1.0 to 1.8 and an axial velocity spread from 3% to 7%. The development of this cusp gun is in progress at the University of Califonia, Davis, for use in the development of harmonic gyrotrons, peniotrons, and gyro-traveling-wave tubes. [ABSTRACT FROM AUTHOR]