外开槽同轴波导大轨道回旋自谐振脉塞放大器

运用大轨道电子束,对外开槽同轴波导回旋自谐振放大器进行了线性动力学理论分析和非线性自洽模型模拟。由线性动力学理论分析和非线性模拟得到的结果在线性增长部分吻合得很好。为了有效抑制绝对不稳定性,对电子束流的选择进行了讨论。计算结果表明：对于电压为700 kV, 电流为100 A, 电子束纵横向速度比为0.8的大轨道电子束, TE51外开槽同轴波导回旋自谐振脉塞放大器的峰值功率和峰值效率分别可以达到6.27 MW和8.96%。     

外开槽同轴波导大轨道回旋自谐振脉塞放大器

 运用大轨道电子束,对外开槽同轴波导回旋自谐振放大器进行了线性动力学理论分析和非线性自洽模型模拟。由线性动力学理论分析和非线性模拟得到的结果在线性增长部分吻合得很好。为了有效抑制绝对不稳定性,对电子束流的选择进行了讨论。计算结果表明：对于电压为700 kV, 电流为100 A, 电子束纵横向速度比为0.8的大轨道电子束, TE₅₁外开槽同轴波导回旋自谐振脉塞放大器的峰值功率和峰值效率分别可以达到6.27 MW和8.96%。     

圆柱开槽波导的FEM放大器数值研究

对圆柱开槽波导、螺旋摇摆器为模型,考虑了电子初始速度零散、引导磁场等效应对放大器饱和特性的影响,导出了自治的注波互作用三维非线性方程组,并在此基础上编制了相应的计算软件,通过数值分析的方法研究了圆柱开槽波导自由电子激光放大器的饱和效率、频带宽度等高频特性。     

两级回旋行波放大管结构参量对管子性能影响的分析

对两级开槽回旋行波放大管注波互作用进行了自洽非线性数值计算,分析了分隔段的长度、位置以及第一级、第二级高频波导的长度对注波互作用的影响情况,模拟了电子注速度离散对效率、增益、带宽的影响。电子注的运动为绕轴大回旋运动。     

圆柱开槽波导FEM放大器数值研究

以圆柱开槽波导、螺旋摇摆器为模型,考虑了电子初始速度零散、引导磁场等效应对放大器饱和特性的影响,导出了自洽的注波互作用三维非线性方程组.并在此基础上编制了相应的计算软件,通过数值分析的方法研究了圆柱开槽波导自由电子激光放大器的饱和效率、频带宽度等高频特性.     

具有分布损耗波导结构的回旋行波放大器绝对不稳定性

 详细推导了具有分布损耗波导结构的回旋行波放大器的色散特性。通过绝对不稳定性振荡出现的条件,给出求解具有损耗波导结构回旋行波管放大器的绝对不稳定性起振电流的数值计算方法。研究结果表明：绝对不稳定性起振电流与损耗波导的集肤深度有关,选择有较大的集肤深度的损耗波导可以提高绝对不稳定性起振电流;绝对不稳定性起振电流同时也与工作磁场偏离饱和磁场的程度以及电子束的纵横速度比有关;通过设计具有分布损耗波导结构的注-波互作用电路,以及工作磁场、电子束的纵横速度比,可以在兼顾带宽、效率的条件下,保证回旋行波管放大器稳定工作。     

具有分布损耗波导结构的回旋行波放大器绝对不稳定性

详细推导了具有分布损耗波导结构的回旋行波放大器的色散特性。通过绝对不稳定性振荡出现的条件,给出求解具有损耗波导结构回旋行波管放大器的绝对不稳定性起振电流的数值计算方法。研究结果表明：绝对不稳定性起振电流与损耗波导的集肤深度有关,选择有较大的集肤深度的损耗波导可以提高绝对不稳定性起振电流;绝对不稳定性起振电流同时也与工作磁场偏离饱和磁场的程度以及电子束的纵横速度比有关;通过设计具有分布损耗波导结构的注-波互作用电路,以及工作磁场、电子束的纵横速度比,可以在兼顾带宽、效率的条件下,保证回旋行波管放大器稳定工作。     

Ka波段螺旋波纹波导回旋行波管

螺旋波纹波导回旋行波管与采用圆波导的回旋行波管相比,有较大的带宽。介绍了它的线性注波互作用理论,并用该理论计算了不同的磁场与波导表面微扰幅度对Ka波段螺旋波纹波导回旋行波管线性增益的影响。计算结果与已报道的实验结果基本符合,说明该理论可以初步确定螺旋波纹波导回旋行波管的各项参数。     

Ka波段螺旋波纹波导回旋行波管

螺旋波纹波导回旋行波管与采用圆波导的回旋行波管相比,有较大的带宽。介绍了它的线性注波互作用理论,并用该理论计算了不同的磁场与波导表面微扰幅度对Ka波段螺旋波纹波导回旋行波管线性增益的影响。计算结果与已报道的实验结果基本符合,说明该理论可以初步确定螺旋波纹波导回旋行波管的各项参数。     

螺旋波纹波导模式分析

通过螺旋波纹波导的耦合波方程,考虑到波的左右旋转方向及波的前向和反向等因素,给出了波导中可能存在的所有模式,由耦合方程的特点和布拉格条件分析了各模式之间的关系,给出对应于螺旋波纹波导回旋行波管和螺旋波纹波导回旋返波管的模式耦合特点,并给出耦合关系和波导的模式耦合规则。结合螺旋波纹波导的色散方程,讨论了不同波纹周期和波纹起伏程度对模式耦合的影响：波纹周期的增大,使得电子注的加速电压变大;如果波纹周期太小,则工作模式线性变得很差。阐述了螺旋波纹波导回旋行波管克服模式竞争的机理。纹起伏程度较大,工作模式和非工作模式分离程度变大,对克服模式竞争比较有利。     

Numerical simulation and experimental study of magnetron injection guns of high-power shortwave gyrotrons

The results of numerical simulation and experimental study of magnetron injection guns for high-power gyrotrons that form intense helical electron beams are compared. Three types of beams are studied: those with regularly intersecting trajectories, laminar, and mixed (with irregularly intersecting trajectories). The corresponding guns differ in the angle of inclination of the emitting surface to the axis of axial symmetry. Numerical simulation was performed using the ÉPOS program, which takes into account the effect of the space-charge field on the velocity distribution. The experimental studies of the latter were performed by the retarding-field method. It is established that with allowance for temperature deformations of the electrode systems, the experimental data are in satisfactory agreement with the theoretical. It is shown that for a maximal beam current, the best velocity-distribution characteristics (velocity spread and pitch factor) are provided by guns that form laminar and boundary beams (an intermediate case between laminar and regularly intersecting beams).     

Effect of electron velocity spread on gyro-peniotron efficiency

The paper describes the influence of the velocity spread of the electrons on the interaction efficiency and on other operational characteristics in the gyro-peniotron oscillator. Numerical simulation shows a drastic efficiency reduction from more than 45% to less than 30% with an electron velocity spread of 10% for a 35GHz, TE₀₃ mode gyro-peniotron operating at the third harmonic. The operation ranges of the device parameters at a defined efficiency level are also decreased when the velocity spread of the electrons increases.     

Experimental investigation of a 140 GHz gyrotron-backward wave oscillator

We report the experimental operation of a voltage tunable gyrotron backward wave oscillator (gyro-BWO) in the frequency range near 140 GHz. Voltage tunability is an important feature of the gyro-BWO for application as a fast tuning source for driving high power free electron lasers or cyclotron autoresonance maser amplifiers. The gyro-BWO operated in an overmoded cylindrical waveguide structure in the TE_1,2 mode. The electron beam source was a Pierce-wiggler gun producing an 80 kV, 6.2 A beam. Frequency tuning with voltage between 134 and 147 GHz was achieved in the TE_1,2 mode with constant magnetic field. However, this tuning was found to be discontinuous. Output powers of up to 2 kW and 2% efficiency were found, significantly below theoretical predictions for a cold beam. The theoretical beam velocity spread was modeled by a 3D beam transport code. The code results show that space charge forces, coupled with the wiggler-induced helical motion and the short cyclotron wavelength of the beam, produce large increases in velocity spread in the magnetic compression region. A beam with smaller velocity spread would be needed to make the gyro-BWO operate at the desired efficiency.     

Limiting current of helical electron beams in gyrotrons

Potential depression (PD) and limiting current (LC) of helical electron beams (HEB) are investigated. Nonneutral electron beams and two velocity distributions: uniform and Rayleigh distribution are taken into account. For Rayleigh distribution electron reflection from magnetic mirror is taken into account. It is shown that velocity spread may lead to substantial reduction of LC for real values of the mean pitch-factors of helical trajectories. PD and LC are an unmonotonous functions of the velocity spread for Rayleigh distribution. A connection of PD with the change of gyrofrequency and with the beam broadening in gyrotron operating space is retraced.     

Experimental and numerical studies of sheet electron beampropagation through a planar wiggler magnet

Detailed experimental studies on sheet relativistic electron beam propagation through a long planar wiggler are reported and compared with numerical simulations. The planar wiggler has 56 periods with a period of 9.6 mm. Typically, the wiggler field peak amplitude is 5 kG. The experimental efforts are focused on controlling the deviation of the beam toward the side edge of the planar wiggler along the wide transverse direction. It is found that a suitably tapered magnetic field configuration at the wiggler entrance can considerably reduce the rate of deviation. The effects of the following techniques on beam transport efficiency are discussed: side focusing, beam transverse velocity tuning at the wiggler entrance, and beam spread limiting. High beam transport efficiency (almost 100%) of a 15-A beam is obtained in some cases     

Improvement of the helical electron beam quality and the gyrotron efficiency by controlling the electric field distribution near a magnetron injection gun

A technique for controlling the electric field distribution near the cathode of a magnetron injection gun is developed. The feasibility of improving the quality of a helical electron beam by optimizing the electric field distribution in a pulsed 4-mm-wave gyrotron is studied theoretically and experimentally. Field distributions are obtained that minimize the electron velocity spread in the beam, coefficient of electron reflection from a magnetic mirror, and intensity of parasitic low-frequency oscillations. It is demonstrated that the gyrotron efficiency can be increased through a rise in the beam quality at the optimized electric field distribution.     

170GHz兆瓦级同轴回旋振荡管的分析计算

回旋管是最有希望应用于正在实施的国际热核实验反应堆计划的微波源器件,然而研究设计符合要求的回旋管还存在很多困难需要解决.对170 GHz兆瓦级光滑同轴回旋管的注-波互作用进行了研究.选取模式谱相对稀疏的TE31,12作为工作模式,利用Matlab编制源程序,计算了同轴回旋管的注-波耦合系数、起振电流.在考虑电子速度零散、腔壁电阻率和单模近似的基础上,对光滑同轴谐振腔的优化设计和注-波互作用进行了仿真,给出了磁场、电压、电流和内导体倾角等参量与回旋管效率的关系.结果表明,电压和磁场对回旋管效率影响较大,电子速度零散对回旋管效率影响较小,因而可降低电子枪的设计要求.此外,优化内导体倾角和同轴谐振腔结构参数可提高注-波互作用效率,降低电子速度零散对互作用效率的影响,获得了约50%的电子效率及1.7 MW输出功率.     

直线感应加速器模拟软件多功能发射模块开发

在模拟直线感应加速器电子束输运过程中,为了正确设置注入器电子束参数,以注发射模型为基础,研发了可设置发射度、能散和电子束倾斜的多功能发射模型。理论研究了发射度、能散以及电子束倾斜角度,并将这些理论实现到发射模块上。建模对多功能发射模块进行测试,比较设定的电子束参数与模拟测定的电子束参数。通过比较,观测到设定电子束参数与模拟测定值一致,验证了多功能模块开发的正确性。     

Nonlinear simulation of a high-power, collective free-electronlaser

Results obtained with the three-dimensional nonlinear analysis and simulation code, ARACHNE, and a recent 33.4-GHz, collective, free-electron laser (FEL) amplifier experiment are compared. The experiment has demonstrated power levels of 61 MW (≈27% efficiency) without recourse to tapered magnetic fields, using a 750-keV/300-A electron beam with a nominal axial energy spread of 1.5% propagating through a cylindrical drift tube in the presence of a helical wiggler and an axial guide magnetic field. Significant differences in the character of the emission were found, depending on the direction of the guide magnetic field. When the wiggler and guide fields were parallel, observed power levels reached approximately 4 MW for both the strong and weak guide field regimes, but vanished in the neighborhood of the magnetic resonance. However, the maximum power was observed in the reversed field case when the wiggler and guide fields were antiparallel. In this case, no resonant enhancement in the transverse velocity is expected to occur; however, a significant reduction in the output power occurred in the neighborhood of the antiresonance. The ARACHNE simulation is in substantial agreement with the experiment     

微型无刷直流电机位置系统的过程控制

为了实现机械相控阵列天线的波束扫描,采用微型无刷直流电机驱动螺旋天线单元转动来到达预定的辐射相位。设计了一种新型微型无刷直流电机位置控制系统,构建了比例滑模面-超螺旋二阶滑模控制器用于速度控制,利用结合速度剖面策略的PID控制算法实现了转动位置的中间过程控制。建立了基于Simulink的系统仿真模型,验证了方案的可行性,并构建了FPGA硬件实验平台。仿真和实验结果均表明,微型无刷直流电机驱动天线单元精确按照预设的速度剖面曲线运行,在50 ms控制周期内转动角度达到180°,中间控制过程的位置跟踪误差和平衡位置处的残余震荡误差均小于±3°。