Search

The high-order mode oscillation is studied in designing a four-cavity intense relativistic klystron amplifier(IRKA). The reason of the oscillation caused by high-order modes and a method to suppress this kind of spurious modes are found through theoretical analyses and the study on the influence of major parameters of a high frequency structure (such as, the oscillation frequency of cavities, the cavity Q value, the length of drift tube section and the characteristic impedance etc.). Based on much simulation, a four-cavity Intense Relativistic Klystron Amplifier with a superior performance has been designed, built and tested. An output power of 2.22 GW corresponding to 27.4% efficiency and 61 dB gain has been obtained. Moreover, the high-order mode oscillation is suppressed effectively, And an output power of 1.95 GW corresponding to 26% efficiency and 62 dB gain has been obtained in the laboratory. more...

How to improve the efficiency of the gyrotron is always the focus of attention in studying gyrotron. There are many way to enhance the efficiency of the gyrotron, which are mainly concentrated in two aspects, one is designing the gyrotron with a depressed collector, the another is by changing the cavity structure to improve efficiency. In the paper, we adopt a new cavity structure which can better inhibit mode competition and get higher coupling efficiency. the gyrotron with the new cavity has been optimized and simulated. An output power more than 1.5 MW is obtained at the accelerating beam voltage of 80 kV, the beam current of 45 A, the transverse-to-axial velocity ratio of 1.3, corresponding to the overall efficiency of 47.2%. more...

How to improve the efficiency of the gyrotron is always the focus of attention in studying gyrotron. There are many way to enhance the efficiency of the gyrotron, which are mainly concentrated in two aspects, one is designing the gyrotron with a depressed collector, the another is by changing the cavity structure to improve efficiency. In the paper, we adopt a new cavity structure which can better inhibit mode competition and get higher coupling efficiency. the gyrotron with the new cavity has been optimized and simulated. An output power more than 1.5 MW is obtained at the accelerating beam voltage of 80 kV, the beam current of 45 A, the transverse-to-axial velocity ratio of 1.3, corresponding to the overall efficiency of 47.2%. more...

Based on the mode-matching technique and simulation software CST, this paper analyzes and simulates the input cavity of gyroklystron amplifier, and gets the structure model of TE01 mode W-band gyroklystron input cavity. Then it contrasts the influence of the size of coupling slots to the coupling frequency and Q-value. more...

A complex cavity with gradual transition is employed in the 94 GHz gyrotron. A self-consistent field nonlinear theory has been used and numerical simulations for electron beam interaction with RF modes are given. A pulse output power of 235.2 kW is obtained by simulation at a beam voltage of 60 kV with beam current of 10 A, a velocity ratio of 1.45, and magnetic field 17kG, corresponding to an efficiency of 39.2%. more...

Cyclotron electron beam provided by magnetron injection gun has a direct impact on the performance of the whole gyro-devices. Based on the initial study and computer simulations, A 10 A single-anode electron gun has been studied and designed according to the requirements of the gyrotron. Calculations have been performed to optimize the electrode shape and the beam parameters. The electron beam with a beam pitch ratio of 1.5 and a low velocity spread of 4% are obtained. more...

A complex cavity with gradual transition is employed in the W-band gyrotron. A self-consistent field nonlinear theory has been used and numerical simulations for electron beam interaction with RF modes are given. A pulse output power of 212 kW is obtained by simulation at a beam voltage of 60 kV with beam current of 10 A, a velocity ratio of 1.5, and magnetic field 17kG, corresponding to an efficiency of 35.3%. more...

In this paper, we improve the trilateral filter for removing the mix of Gaussian and impulse noise. The new algorithm incorporates Rank-Ordered Absolute Differences (ROAD) Statistic for detecting outliers in gradient domain and intensity domain of image with impulse noise. A switching mechanism is adopted in gradient bilateral filter and intensity bilateral filter for smoothing the gradients and intensities of impulse noise samples and impulse noise-free samples with different parameters. By introduce the impulse detector in both gradient domain and intensity domain, the proposed algorithm has demonstrated superior performance in suppressing noise, which include Gaussian, impulse, and mixed noise. Compared to most other nonlinear filters, the proposed algorithm consistently yields good results in a sharply-bounded, gradient piecewise-linear approximation which provides stronger noise reduction and better edge-limited smoothing behavior. more...

Based on the quasi-self-consistent field nonlinear theory the simulation software GKER (Gyroklystron emulator) was developed for the calculations and simulation of the interaction between electron beam and RF field in gyroklystrons using the union programming technique. This paper mainly discusses the simulation results of the resonators designed for the experimental Gyroklystrons using GKER. more...

Summary form only given. Recently, gyrotron-based spectrometers suitable for nuclear magnetic resonance (NMR) studies have been constructed to study dynamic nuclear polarization which can result in significant enhancement of the NMR signal. In the present paper multimode calculations of a low-power (above 10W) high-frequency (200 GHz -300 GHz) gyrotron for NMR spectroscopy applications have been performed. The co- rotating TE-7,2 mode has been chosen to be the main operating cavity mode. Five neighbor modes (TE7,2; TE-4,3; TE4,3; TE-2,4; TE2,4) whose coupling factors are above 30% of the main mode and most probably can be excited in the cavity are included into the calculation using the FZK SELFT code packet designed for time dependent and self-consistent multimode calculations. The frequency fine tuning was obtained via the excitation of a sequence of longitudinal modes of TE-7,2,q by varying the beam voltage from 15 kV upward and the magnetic field from 9.6 T to 9.77 T. The results show that the main mode TE-7,2 is quite stable against the possible transverse mode competitors within this magnetic field range and a continuous frequency tuning range more than 800 MHz (263.43 GHz - 264.28 GHz) has been achieved with a velocity ratio of 1.3, the beam radius and current being 1.33 mm and 100 mA respectively. more...

A systematic theoretical study of gyroklystrons with a series of abrupt transitions along the axial has been done already. A quasi-self-consistent field nonlinear theoretical investigation and a result of numerical simulation of electron beam interacting with RF field in a gyroklystron are presented in this paper. Parameters of Ka band gyroklystrons were calculated for designs using this theory and they provide useful information for experiments and further study. more...

Open cavity with abrupt changes is generally used in the gyro-oscillators and amplifiers. On the basis of mode-matching technique we present the high frequencies structure analyses code for gyrotron. The code provides a method for computing the resonant frequency and Q value in an open cavity. We present the theory and an example which demonstrates the operation and the possible usage of the code. more...