Study of a 35-GHz third-harmonic low-voltage complex cavitygyrotron

A self consistent nonlinear theoretical model for a complex cavity gyrotron with abrupt transitions is presented in this paper. The model accounts for mode conversion in the transition region of the complex cavity through the general theory of modal expansion techniques. The interaction between the electron beam and TE₆₁/TE₆₂ RF field in the step cavity for a third-harmonic gyrotron is simulated; many calculations are carried out under different electron beam parameters     

Self consistent code for a 150 GHz gyrotron

A self consistent calculation for gyrotron oscillators is described and applied to a TE₀₃ mode gyromonotron. The RF field profile satisfies a wave equation in which the AC beam current appears as a source. The wave equation is solved simultaneously with the electron equation of motion.     

微波谐振腔中电子与微波作用的非稳态过程研究

 在微波腔中微波场影响电子的运动，同时电子束作为电流源也产生辐射，影响微波场，这种相互作用包含线性和非线性过程。根据Maxwell理论，微波腔中的实际微波场可以按微波腔的模式展开，而且不同模式与电子束之间的相互作用不同。将电子束作为激励源，根据Maxwell方程和电子受到的洛伦兹力，建立不同模式在电子束作用下的激励方程和电子束电子在不同模式作用下的运动方程（即微波谐振腔中电子束与微波场相互作用的自洽方程组），并由此进一步分析一维情况下单间隙微波腔中微波建场、辐射场呈指数增长和饱和等非稳态作用过程，该过程涉及到电子束与微波作用的线性和非线性过程。     

Third-harmonic complex cavity gyrotron self-consistent nonlinearanalysis

Starting from general transmission line equations with an electron beam source, a self-consistent nonlinear theoretical model for a complex cavity gyrotron with gradual transitions is presented in this paper. The model accounts for mode coupling in the transition region of the complex cavity. The interaction between the electron beam and H₆₁-H ₆₂ RF field in the complex cavity for a third-harmonic gyrotron is simulated; many calculations are carried out under different cavity dimensions and electron beam parameters     

3 mm波段二次谐波渐变复合腔回旋管的非线性模拟

 利用含电流的传输线方程,并在考虑多模注-波互作用及多模耦合的情况下,利用自主开发的多模高次谐波渐变结构复合腔回旋管的注-波互作用数值模拟软件,对3 mm波段二次谐波渐变复合腔回旋管进行了自洽非线性模拟,分析了H₀₂-H₀₃模式对下磁场系数、电流、电子注速度比对注-波互作用效率的影响。计算结果表明,在合适的腔体结构尺寸下,以及合适的磁场系数、电流、速度比下,注-波互作用效率可达27％。     

Eccentricity of the electron beam in a gyrotron cavity

Dependence of the coupling of the electron beam and RF field in a gyrotron cavity on eccentricity of the electron beam is studied.     

8mm波段三次谐波复合腔回旋管的非线性分析

利用含电流的传输线方程,在考虑了诸多实际因素影响的情况下,对三次谐波渐变复合腔回旋管进行了自洽非线性模拟,计算了H₅₁₁-H₅₂₁模式下三次谐波多模注波互作用,分析了电子注的厚度、速度零散、速度比α值及磁场波动对多模注波互作用的影响 关键词： 回旋管 复合腔 多模注波互作用 速度零散 速度比α     

渐变复合腔回旋管高次谐波注-波互作用非线性模拟

利用含电流的传输线方程,在考虑多模与电子注互作用及多模耦合的情况下,对三次谐波渐 变复合腔回旋管进行了非线性模拟,计算了H₅₁-H₅₂模式下三次谐 波注波互作用,分析了多模对注-波互作用的影响. 关键词： 回旋管 渐变复合腔 多模注-波互作用 模式耦合 高次谐波     

W波段二次谐波突变复合腔回旋管数值模拟

 通过对二次谐波低电压突变结构复合腔回旋管中谐振腔结构、模式竞争以及电子注-波互作用的研究,分析了高频结构特性、寄生模式的抑制和工作参数优化等问题。给出了3 mm 二次谐波低损耗TE₀₂/TE₀₃模式回旋管的模拟设计结果。计算采用了坡度磁场,互作用效率得到显著提高。PIC粒子模拟结果表明:在电子注电压25 kV、电流4 A、纵横速度比1.6、工作磁场1.72 T时,回旋管可获得37 kW 的输出功率,横向运动能量转换效率高达51%,器件效率为37%。     

A 35-GHz low-voltage third-harmonic gyrotron with a permanent magnet system

A systematic theoretical and experimental study on a 35-GHz 45-kV third-harmonic gyrotron with a permanent magnet system is presented in this paper. A complex cavity with gradual transition and a diode magnetron injection gun (MIG) are employed in the gyrotron. A self-consistent field nonlinear theoretical investigation and numerical simulation for electron beam interaction with RF fields are given. The diode MIG is simulated numerically utilizing our code in detail. The permanent magnet system provided the maximum axial magnetic field of about 4.5 kG in the cavity region of the gyrotron. The Ka band third-harmonic complex cavity gyrotron with a permanent magnet system has been designed, constructed, and tested. A pulse output power of 147.3 kW was obtained at a beam voltage of 45 kV with beam current of 32.2 A, corresponding to an efficiency of 10.2%.     

新型金属丝靶电子源实验研究

电子束在基础科学研究、工农业生产和医疗领域发挥了重要作用。提出了一种新型的电子源技术方案:高功率激光脉冲轰击金属丝靶,可以产生大量能量在百keV量级的热电子,一部分热电子在丝靶表面自生电磁场的作用下沿着丝靶运动,丝靶后方可以获得指向性良好的电子束。实验上成功在金、钨和铜丝靶后方获得了电子束团,测量了束团束斑、电荷量和能谱。铜丝靶单发实验收集到的电子束团总电荷量可达3 nC,能量分布在0～240 keV区间内,能谱在100 keV附近呈现峰值。提出了微波压缩方案,设计了2腔微波聚束腔,利用ASTRA对微波腔压缩过程进行了模拟计算。结果显示,可以将电荷量1 nC、长度55 ps的束团压缩至27 ps,满足后续微波加速器对电子源的要求。     

A new approach for a multistage depressed collector for gyrotrons

A feasibility study for a two-stage depressed gyrotron collector has been performed. A new approach for an adiabatic magnetic decompression of the hollow electron beam has been used. It permits control of the radius of the constant magnetic flux surface, which determines the radial extension of the electron beam. Independent of the value of the magnetic field around the beam. For this purpose, either solenoidal coils or a ferromagnetic insert can be placed inside the hollow electron beam. Thus, the radial dimensions of a multistage depressed collector of a high-power high-frequency gyrotron can be kept within limits given by technological constraints. The energy sorting of the electron beam is improved by using electrodes inside the hollow electron beam for controlling the potential distribution. The additional control electrodes make it possible to eliminate almost all of the effect of secondary electrons on the operation of the collector. In order to demonstrate the proposed approach, a compact two-stage depressed collector has been designed for a 1.5-MW coaxial cavity gyrotron operating at 165 GHz in the transverse electric (TE)_31,17 mode, which is under development at FZK, Karlsruhe, Germany. Including the effect due to secondary electrons, a collector efficiency of 73% has been calculated with an average and peak heat dissipation density of about 240 W/cm² and 500 W/cm², respectively. This results in an increase of the output gyrotron efficiency from 36.5% to 62.6% when internal radio frequency (RF)-losses inside the gyrotron tube of 15% are taken into account     

Numerical modeling of large orbit magnetron-type gyrotron throughself-consistent nonlinear theory

Self consistent nonlinear theory is applied to analyze the large orbit magnetron-type gyrotron in detail; many calculations are carried under different cavity dimensions and electron beam parameters. The influence of electron beam thickness and output structure is taken into consideration. Dimensions of a 16 slot, 35 GHz, 8th harmonic tube are given     

任意时间分布电子束与单间隙微波腔的非线性自洽过程研究

将电子束作为激励源，根据Maxwell方程和电子受到的洛伦兹力，给出了描述工作模式在电 子束作用下的激励方程和电子束电子在工作模式作用下的运动方程（即微波谐振腔中电子束 与微波场相互作用的自洽方程组）.根据该自洽方程组，进一步研究了任意时间分布电子束 与单间隙微波腔的相互作用.通过分析微波腔中电子束与微波作用的线性和非线性过程，给 出了电子束调制深度、微波腔作用间隙对微波输出功率的影响.最后从理论上给出了影响微 波输出功率的综合物理参量. 关键词： 微波腔 模式 自洽方程 单间隙微波腔     

94GHz基波复合腔回旋管数值模拟

通过对94 GHz基波复合腔回旋管中谐振腔结构、电子注参数以及注-波互作用过程的模拟计算研究,分析了复合腔回旋管的高频结构特性和工作参数优化问题.给出了基波H61 -H62模式对复合腔回旋管的模拟设计结果.数值模拟结果表明:在电子注电压40 kV、电流5A、电子横纵速度比1.3、工作磁场3.6T时,回旋管可获得78 k...     

Numerical simulation of processes in a 170 GHZ/1 MW CW gyrotron cavity with operating mode TE 25.10 for iter

We consider a gyrotron for the ECR plasma heating complex of ITER. Gyrotron cavity parameters are optimized with allowance for ohmic losses, reradiation of waves due to profile inhomogeneities, potential depression, and velocity spread of the electron beam. We study the effect of ion compensation for the space charge, the onset of oscillations after switching on the gyrotron, and the competition between operating and spurious modes. The possibility of obtaining 35–39% efficiency without electron-beam energy recovery and 55–60% efficiency with a one-stage depressed-potential collector is shown for cavity RF ohmic loss power less than 2 kW/cm². Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 3, pp. 225–234, March 1999.     

A High-Efficiency Second-Harmonic Gyrotron with a Depressed Collector

The gyrotron with an electrically insulated collector has been manufactured and tested. The 60% output efficiency is obtained for the Collector Potential Depression (CPD) operation regime. The results of the numerical simulation of the electron energy spectrum in the collector region of the second-harmonic technological 24 GHz gyrotron are presented. It is shown, that the minimal electron beam energy is about 20% of the initial value and that the gyrotron cavity should be expanded to achieve the highest output efficiency of the gyrotron with energy recovery. The highest experimental decelerating voltage is in good agreement with the calculation of the electron energy spectrum.     

光子带隙谐振腔回旋管振荡器的自洽非线性理论

定义了光子带隙谐振腔(photonic-band-gap cavity, PBGC)的等效半径,论证了使用该半径将PBGC等效为具有模式选择性的金属圆柱谐振腔的有效性,揭示了其在PBGC设计过程中的指导性作用.基于等效半径的运用,建立起光子带隙谐振腔回旋管振荡器(PBG回旋管)的自洽非线性理论,并对工作于TE₃₂模的PBG回旋管作了理论分析和数值计算.目前的研究表明:高频电磁场沿角向呈行波或驻波的不同极化形式对PBG回旋管的注-波互作用过程具有较大的影响;较之电子回旋基波,该器件中二 关键词： 光子带隙谐振腔 等效半径 回旋管 自洽非线性理论     

Efficient Low-Voltage Operation of a CW Gyrotron Oscillator at 233 GHz

The gyrotron oscillator is a source of high average power millimeter-wave through terahertz radiation. In this paper, we report low beam power and high-efficiency operation of a tunable gyrotron oscillator at 233 GHz. The low-voltage operating mode provides a path to further miniaturization of the gyrotron through reduction in the size of the electron gun, power supply, collector, and cooling system, which will benefit industrial and scientific applications requiring portability. Detailed studies of low-voltage operation in the TE(2) (,) (3) (,) (1) mode reveal that the mode can be excited with less than 7 W of beam power at 3.5 kV. During CW operation with 3.5-kV beam voltage and 50-mA beam current, the gyrotron generates 12 W of RF power at 233.2 GHz. The EGUN electron optics code describes the low-voltage operation of the electron gun. Using gun-operating parameters derived from EGUN simulations, we show that a linear theory adequately predicts the low experimental starting currents.     

Nonlinear Analysis of A Slotted Third-Harmonic Gyro-TWT Amplifier

The distribution of RF field of the slotted cylindrincal waveguide is discussed and the self-consistent nonlinear theory of the beam-wave interaction is presented in this paper.The behavior of the 95-GHz slotted third-harmonic gyrotron traveling-wave amplifier (gyro-TWT) with a uniform section is simulated by a Runge-Kutta algorithm code for an axis-encircling electron beam with velocity spread. Some important relations in the process of the beam-wave interaction are abtained and analyzed.