70 GHz二次谐波倍频回旋速调管研究

 对70 GHz二次谐波倍频回旋速调管高频结构和电子与波互作用进行了研究。研究了TE02模腔体绕射品质因数及模式转化,解决了二次谐波倍频回旋速调管漂移段不能截止70 GHz的TE01模而引起的腔体间高频串扰的问题。分析了注电流、输入功率、电子横纵速度比和电子注引导中心半径等参数对输出功率、增益和效率的影响。针对二次谐波回旋速调管放大器工作频带窄、效率低,进行了高频结构优化设计,显著地展宽了工作频带,提高了互作用效率。在理论分析和高频计算的基础上,建立了注-波互作用PIC（粒子模拟）模型,进行了粒子模拟计算和优化,得到了70 GHz 的二次谐波倍频四腔回旋速调管放大器设计方案。粒子模拟结果表明：在工作电压70 kV,注电流13 A,电子注横向速度与纵向速度比为1.5时,中心频率69.81 GHz输出功率256 kW,带宽160 MHz,电子效率28%,饱和增益大于44 dB。     

Ka波段二次谐波回旋速调管放大器的输出特性

根据谐波回旋速调管放大器的注-波互作用特点,对Ka波段二次谐波三腔回旋速调管放大器的输出腔进行了数值模拟和优化设计,获得了输出腔末端高频波绕射输出孔径和腔体绕射Q值的对应关系。通过PIC粒子模拟,分析了该放大器的频率响应特点等输出特性。结果表明,在35 GHz频率,磁场0.685 T,电子注电压70 kV,电流15 A,横纵速度比为1.45,输入功率1.6 kW时,放大器可以获得超过220 kW的峰值输出功率、约22%的效率和23 dB的增益,3 dB带宽可达到110 MHz。     

Ka波段二次谐波回旋速调管放大器的输出特性

 根据谐波回旋速调管放大器的注-波互作用特点,对Ka波段二次谐波三腔回旋速调管放大器的输出腔进行了数值模拟和优化设计,获得了输出腔末端高频波绕射输出孔径和腔体绕射Q值的对应关系。通过PIC粒子模拟,分析了该放大器的频率响应特点等输出特性。结果表明,在35 GHz频率,磁场0.685 T,电子注电压70 kV,电流15 A,横纵速度比为1.45,输入功率1.6 kW时,放大器可以获得超过220 kW的峰值输出功率、约22%的效率和23 dB的增益,3 dB带宽可达到110 MHz。     

100-150 MW designs of two- and three-cavity gyroklystron amplifiersoperating at the fundamental and second harmonics in X- andKu-bands

Efficient 100-150 MW X- and Ku-band microwave sources with pulselengths of 1 μs are being developed for driving future linear colliders. Two- and three-cavity co-axial designs of relativistic gyroklystron amplifiers are presented here which fulfill these requirements. Numerical simulations predict over 40% efficiency, 45-50 dB gain, and 100-160 MW power level for the gyroklystron designs operating at fundamental (8.568 GHz) and second harmonic (17.136 GHz). It is shown that introducing a penultimate (buncher) cavity significantly improves efficiency and gain of the second-harmonic amplifier     

95 GHz三次谐波回旋管设计

采用线性理论和非线性理论研究了回旋管谐振腔结构、寄生模式抑制及注波互作用等问题。设计了一支工作在95 GHz的三次谐波回旋管,注波互作用结构采用标准开放式谐振单腔,工作模式为TE64, 采用电压45 kV、电流5 A、横纵速度比为1.5的小回旋电子注。在不考虑电子注速度离散及厚度的情况下,非线性理论分析表明,该回旋管可以获得14 kW功率输出,横向互作用效率约为18%,整管效率约11%。     

Measurements of velocity ratio in a 90 MW gyroklystron electronbeam

Measurements of the ratio of perpendicular to parallel velocity (α=υ_⊥/υ,) in a 390-420 kV, 160-240 A, small orbit gyroklystron electron beam produced by a magnetron injection gun have been performed using a capacitive probe. The probe employed guard rings to reduce uncertainties in measurement and calibration due to fringing electric fields. These studies represent the first measurements of a in such a powerful rotating beam. Since the current levels in this experiment are two to three times higher than those in previous velocity ratio studies of beams with similar voltage. The effects of changes in voltage, current, and magnetic compression on the measured velocity ratio are investigated. Values of α in the range of 0.8-1.3 are typically observed, which are considerably higher than the values predicted by theoretical simulations. Errors in the modeling of space charge effects are ruled out as the cause of the discrepancy by the agreement between theoretical and experimental space charge current limits. Instead, a significant portion of the discrepancy is attributed to a reduction in cathode magnetic field by the self-axial magnetic fields of the electron beam     

Theory and simulation of an 85 GHz quasioptical gyroklystron experiment

The linear theory used to design a two-resonator 85 GHz quasioptical gyroklystron with a nonuniform magnetic field is presented. It is shown that a tapered magnetic field in the prebunching resonator has a relatively small effect on the electron bunching parameter. The effect of velocity spread of the electron beam can be minimized by adjusting the magnetic field strength in the two resonators. Measured amplifier performance is in good agreement with calculations from the nonlinear multimode simulation code. Gyrophase bunching of the electrons is preserved over the long drift region (30 radiation wavelengths) even though no attempt has been made to minimize the velocity spread of the beam.     

Cavity design and linear analysis of 225 GHz frequency-quadrupling gyroklystron

This paper considers the frequency-quadrupling three-cavity gyroklystrons with successive frequency-doubling in each cavity. The cavities of 225~GHz frequency-quadrupling gyroklystron are designed with the scattering matrices method and the possible operating mode are discussed. With the point-gap theory, the starting currents of the possible operating modes and the potential parasitic modes in the output cavity are calculated. The optimal operating mode is proposed under consideration of the mode competition and the power capacity of the cavity.     

95 GHz TE03模回旋管内置渐变波导设计

在耦合波理论的基础上,结合波导渐变曲线给出了普适高阶渐变波导设计方法,研究了95 GHz回旋管内置 TE03模式改进Dolph-Chebychev渐变波导。采用编制的数值计算程序进行优化,得到了可靠的最优几何参量,设计出了紧凑的95 GHz渐变波导。经全电磁场仿真验证,该内置渐变输出结构对杂模的抑制达30 dB,满足设计要求。回旋管的热测实验中测出的模式样图表明,所设计的内置渐变波导有效地实现了回旋管内径变化。该方法可以高效地指导高阶过模圆波导渐变结构的设计。     

Design of a TE42,7 coaxial cavity for a 1 MW, 280 GHz gyrotron

To provide the required mode selectivity for a 1 MW, 280 GHz gyrotron, a coaxial resonator operating in the high order TE_42,7 mode is considered. Mode discrimination is achieved both by exploring selective ohmic effects and examining the electrodynamic properties of the coaxial cylindrical waveguide. Analytic results indicate the effectiveness of a coaxial insert with a low electrical conductivity in rarefying the mode density of overmoded, megawatt hollow cavities.     

回旋速调管双阳极磁控注入电子枪的设计与优化

根据8 mm回旋速调管放大器对双阳极磁控注入电子枪的要求,分析了电极形状、阳极电压、磁场、注电流对电子注横纵速度比和速度零散的影响,并进行了粒子模拟。分析表明：这些因素可归根为电场和磁场的作用,阴极附近高的电场有助于提高横纵速度比和降低速度零散;而高的磁场及低的磁压缩比将降低横纵速度比,但对速度零散影响无明显规律。在此基础上通过优化电极形状、磁场分布、电流、第一阳极电压和第二阳极电压,模拟并试制出工作电压65 kV、电流12 A、磁场1.4 T的双阳极电子枪,得到的横纵速度比值为1.4,横向速度零散为4.5%, 为8 mm回旋速调管提供了稳定高质量的电子注。     

回旋速调管双阳极磁控注入电子枪的设计与优化

 根据8 mm回旋速调管放大器对双阳极磁控注入电子枪的要求,分析了电极形状、阳极电压、磁场、注电流对电子注横纵速度比和速度零散的影响,并进行了粒子模拟。分析表明：这些因素可归根为电场和磁场的作用,阴极附近高的电场有助于提高横纵速度比和降低速度零散;而高的磁场及低的磁压缩比将降低横纵速度比,但对速度零散影响无明显规律。在此基础上通过优化电极形状、磁场分布、电流、第一阳极电压和第二阳极电压,模拟并试制出工作电压65 kV、电流12 A、磁场1.4 T的双阳极电子枪,得到的横纵速度比值为1.4,横向速度零散为4.5%, 为8 mm回旋速调管提供了稳定高质量的电子注。     

95 GHz TE03模回旋管内置渐变波导设计

在耦合波理论的基础上,结合波导渐变曲线给出了普适高阶渐变波导设计方法,研究了95 GHz回旋管内置 TE03模式改进Dolph-Chebychev渐变波导。采用编制的数值计算程序进行优化,得到了可靠的最优几何参量,设计出了紧凑的95 GHz渐变波导。经全电磁场仿真验证,该内置渐变输出结构对杂模的抑制达30 dB,满足设计要求。回旋管的热测实验中测出的模式样图表明,所设计的内置渐变波导有效地实现了回旋管内径变化。该方法可以高效地指导高阶过模圆波导渐变结构的设计。     

TE_(02)模式95 GHz三次谐波回旋管实验

首次实现W波段三次谐波回旋管输出功率突破10kW。谐波回旋管互作用结构采用带有光阑结构的圆柱型开放式谐振腔,工作模式为低损耗圆对称模式TE02。实验中,在脉冲宽度20μs、电子束电压45kV、电流3A、磁场1.23T时,测得工作频率为95.22GHz,输出功率13.4kW,对应效率9.9%。     

Numerical design of 120 GHz, 1 MW gyrotron interaction cavity

The design and the numerical simulation of the interaction cavity for 120 GHz, 1 MW gyrotron is presented. The optimizations of the cavity parameters are carried out by using the Particle-in-Cell, 3D-electromagnetic simulation code MAGIC. The co-rotating TE_22,6 mode is selected by using the in-house developed code GCOMS. The cold cavity and the beam–wave interaction analyses are carried out to analyze the eigenmode, eigenfrequency and the output power performance. The output power more than 1 MW is achieved at the magnetic field of 4.82 T. The sensitivity analyses of the output power and the frequency with respect to the various interaction cavity parameters are also performed.     

Design of a RF window for 170 GHz, 1 MW gyrotron for ECRH application

This paper describes the design of a large sized diamond window for 1 MW, 170 GHz gyrotron. The diameter and the thickness of the diamond window are 80 mm and 1.482 mm, respectively, whose edge is directly cooled by water. The CST microwave studio has been used for the S-parameter, and finite element analysis code ANSYS has been used for the thermal and the structural simulation. The return loss (S₁₁) and insertion loss (S₂₁) of the 170 GHz gyrotron window have been found −39.80 dB and −0.011 dB, respectively. The thermal and structural analysis of RF window the 397 K temperature at disk center and maximum displacement 0.01 mm has been found in the window disk during the thermal analysis.     

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为了实现对低杂波系统天线的保护需要测量天线温度,根据天线的特征,选择了K型热电偶作为测量工具,使用快速温度巡检仪采集8路热电偶信号,温度数据由软件远程读取显示;为了克服托卡马克带来的电磁干扰,测量回路使用了光纤通信的方法。结果表明,这种方式能够准确实时地反映出天线温度变化,为日后开展天线热保护工作奠定了基础。     

Design of a 35 GHz gyrotron

The conceptual design of a 35 GHz gyrotron has been developed consistently with the complex formulation of the electric field longitudinal distribution in the resonant cavity. Some models of magnetron injection guns able to produce laminar beams have been investigated leading to the design of an electron gun capable of generating a current of 5 A with a perpendicular velocity dispersion of 0.5%. The device includes three magnetic systems producting flat axial magnetic induction profiles of 1.05 kG, 13.2 kG and 0.65 kG in the cathode, cavity and collector regions, respectively. The gyrotron has been designed for pulsed operation in the TE₀₂₁ mode. Under the soft self-excitation condition, the maximum attainable efficiency is 40% with an output power of 100 kW. An analysis of the collector thermal behaviour has been carried out as well as a study of the thermophysical properties of the alumina window to be used.