Simulation of conditions for the maximal efficiency of decimeter-wave klystrons

Using the mathematical model of electron beam transformation in a narrow tube developed by the authors and the KlypWin program suite, conditions for the maximal efficiency of decimeter-wave klystrons having from three to six amplification stages are simulated. Simulation is based on a real electron-optical system and real parameters of the cavities. It is shown that the maximal efficiency (across the load) is 83% for a four-cavity klystron, 86% for a five-cavity klystron, 88% for a six-cavity klystron, and 90% for a seven-cavity one. The electronic efficiency of the simulated seven-cavity klystron equals 94%, which implies the achievement of a global extremum.     

双间隙同轴腔加载波导滤波器输出回路设计

采用高次模同轴输出腔结构和双间隙耦合谐振腔电路结构是提高速调管频率、功率和带宽的两个重要方式。将这两种电路形式相结合,利用等效电路法推导了滤波器加载双间隙耦合输出回路的间隙阻抗实部计算公式。通过等效电路分析和3维电磁场计算软件模拟,研究了降低高次模式双间隙耦合输出回路外观品质因数的方法。最终设计加载滤波器使得输出回路模型带宽达到9.7%。     

Switching speed effect of phase shift keying in SLED for generating high power microwaves

SLAC energy doubler(SLED) type radio-frequency pulse compressors are widely used in large-scale particle accelerators for converting long-duration moderate-power input pulses into short-duration high-power output pulses. Phase shift keying(PSK) is one of the key components in SLED pulse compression systems. Performance of the PSK will influence the output characteristics of the SLED, such as the rise-time of the output pulse, maximal peak power gain, and energy efficiency. In this paper, a high power microwave source based on power combining and pulse compression of conventional klystrons is introduced. The effects of nonideal PSK with slow switching speed and PSK without power output during the switching process are investigated, and the experimental results with nonideal PSK agree well with the analytical results.     

紧凑型矩形波导内功率合成器设计

介绍了一种基于常规速调管功率合成和脉冲压缩的微波源系统,为实现多路高峰值功率速调管的功率合成,设计了一种紧凑型、近平面结构的微波功率合成器。在2.856 GHz频点处,合成器各端口反射损耗和相对端口隔离度均大于45 dB。当两路峰值功率为50 MW的微波功率合成时,合成器内的最大场强约为9.6 MV/m,合成效率大于99%。在四端口功率合成器的基础上,通过两级合成可实现一种八端口微波功率合成器,当四路峰值功率50 MW的微波功率合成时,合成器内最大场强约为13.5 MV/m。     

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A test platform for the TH2103A klystrons and the high power microwave components is developed. The RF driver, four port circulator, RF load and high power cathode power supply are installed on the test bed. A short pulse test is carried out on the test bed. The parameters of the 4 klystrons are optimized by scanning the currents in the 3 focusing coils and the high power microwave transmission components are conditioned. The output power of the 4 klystrons reached 449kW, 417kW, 460kW and 450kW when the pulse duration was 30ms, respectively. The test result is an important reference for the LHCD system on HL-2A tokamak.     

90.4-W all-fiber single-frequency polarization-maintained 1083-nm MOPA laser employing ring-cavity single-frequency seed oscillator

A high-power all-fiber single-frequency polarization-maintained（PM）laser operating at 1 083 nm is demonstrated using a master oscillator power amplifier（MOPA）structure.The seed source of this MOPA laser system is an in-house-built ring-cavity fiber oscillator.Four-stage amplification configuration is employed, in which the maximal output power of the main amplifier is 90.4 W,corresponding to a conversion efficiency of 72.5%.The polarization extinction ratio of the output light is 13 dB.The amplified spontaneous emission is suppressed by a factor of over 25 dB,and no stimulated Brillouin scattering effect is observed when a large-mode-area and high absorption coefficient PM gain fiber is employed.     

基于双抽运参量放大中的信号波和闲频波特性

根据信号波和闲频波所满足的耦合非线性薛定谔方程,导出了双抽运参量放大增益系数g、信号波的放大因子和闲频波转换效率,并在输入总抽运功率不变的情况下,仅改变双抽运功率P1,P2的比值s,对参量放大增益系数g、信号波的放大因子和闲频波转换效率理论研究和数值模拟;数值模拟结果表明：相位匹配条件下,通过改变双抽运功率的比值 ,可获得适当的放大的信号波和一定转换效率的闲频波。     

S波段多注相对论速调管的小信号理论

多注相对论速调管利用多注电子注并行工作,各电子注在传输过程中彼此独立,利于提高注波互作用效率,抑制杂模振荡。分析多注相对论速调管的小信号理论,从谐振腔内电场的场形函数出发确定了不同腔体结构的耦合系数的计算方法,得到了不同电子注形状、注数时的基波电流分量轴向变化过程,并进行模拟验证。结果表明:同轴谐振腔的间隙耦合系数要大于圆柱腔的间隙耦合系数,采用同轴谐振腔更有利于注波互作用;电子群聚过程与每注电子注的势能密切相关,提高电子注数目有助于得到更大的基波电流分量。在电子注电压600 kV、电流5 kA、间隙电压30 kV的条件下,输入腔后的基波电流分量达800 A。     

基于DCS5格式的LDDRK算法

基于五阶线性耗散紧致格式(DCS5)和七级龙格原库塔时间积分算法,根据数值增长因子对精确增长因子的最佳逼近原则,提出与DCS5格式耗散性相适应的优化方法,并得到相应的七级五阶低耗散低色散龙格原库塔(LDDRK)算法.求解标量线性对流方程和线化Euler方程得到的一维波传播问题的数值结果显示,七级五阶LDDRK算法的精度优于七级七阶精度的标准龙格原库塔算法.     

HL-2A 装置低杂波系统高功率速调管调试

建立了低杂波系统调试平台,在此平台上对4 只TH2103A 型高功率速调管及传输线主要部件进行了短脉冲调试,对每只速调管运行参数进行了优化和标定。在50kV/20A 的束电流条件下,速调管工作脉冲脉宽为30ms,4 只速调管输出功率分别为449kW、417kW、460kW 和450kW。测试数据和调试结果为下一步在HL-2A 装置上建设低杂波系统、开展物理实验等提供了重要的参考数据。     

基于双抽运参量放大中的信号波和闲频波特性

根据信号波和闲频波所满足的耦合非线性薛定谔方程,导出了双抽运参量放大增益系数g、信号波的放大因子和闲频波转换效率,并在输入总抽运功率不变的情况下,仅改变双抽运功率P1,P2的比值s,对参量放大增益系数g、信号波的放大因子和闲频波转换效率理论研究和数值模拟;数值模拟结果表明：相位匹配条件下,通过改变双抽运功率的比值 ,可获得适当的放大的信号波和一定转换效率的闲频波。     

双耦合同轴腔TM310模加载空波导输出回路

设计了速调管的单间隙和双间隙圆柱同轴腔高阶TM310模式输出回路。为降低外输出腔的外观品质因数和增加腔内工作模式电磁场的均匀性,采用了在输出孔处腔内侧位置设置轴向短路金属线的措施。由等效电路理论分别计算了它们加载空矩形波导TE10基模时,腔内漂移管中心位置处的等效间隙阻抗及对应的输出带宽。计算模拟发现,与单间隙腔相比,双间隙腔具有较大的间隙阻抗及带宽。     

大间隙C波段三轴速调管束流调制模拟研究

利用SUPERFISH软件设计了一种兼具大间隙速调管及三轴速调管优势的C波段大间隙三轴速调管,对所设计大间隙三轴速调管的束流传输及调制情况进行了2维粒子模拟研究。模拟结果表明,三轴速调管设计需要特别关注"模式泄露"问题以及谨慎选择内导体接地支撑杆的位置,以获得稳定传输的电子束。综合考虑上述两个条件,在440 kV的二极管电压下,5.0 GHz,200 MW的强注入功率可以获得11.8 kA的基频调制积分电流,束流调制深度88%,调制电流峰峰值大于40 kA,且调制电流具有良好的频率及相位稳定性。在此基础上,初步模拟得到了大于2.0 GW的平均微波功率,平均效率约33.8%。     

重入式谐振腔特性参数的解析方法

 对于在速调管中广泛使用的重入式谐振腔以及内部无漂移管的盒形腔，在忽略漂移管壁厚的前提下，导出了能够准确求解其谐振频率的本征方程，并在此基础上进一步计算了腔体的特性阻抗和固有品质因数。针对具体算例的应用表明，由解析式确定的腔体特性参数与SUPERFISH的数值结果具有很好的一致性。     

Computer simulation of a two-stage millimeter-wave klystron oscillator

The results of computer simulation of a two-stage millimeter-wave klystron oscillator are reported. The oscillator consists of two closed-loop floating-drift-tube klystrons with the output cavity of one klystron connected to the input cavity of the other and vice versa. It is shown that 200-W oscillations at a frequency of 95 GHz can be reached by optimizing the coupling coefficient between the cavities and the loaded Q factor.     

速调管2.5维非线性注波互作用程序的研究

在高导流系数的速调管中电子束径及横向速度都会发生显著变化，运动电子与间隙电场之间的能量交换是非线性的互作用过程.为了能准确描述这些现象，我们建立了相应的物理模型并据此编写了用于速调管注波互作用分析的2.5维程序LSP.随后使用该程序针对一个实际的S波段高峰值功率速调管做了详细的计算，与一维程序的计算结果和实测数据的比较表明LSP程序的计算值具有更好的准确性且与实测值很好地一致. 关键词： 速调管 2.5维 注波互作用     

高功率速调管双管功率合成可行性与技术方案研究

对由两支500kW高功率速调管功率合成得到1MW长脉冲低混杂波(LHCD)微波源的可行性进行了分析,并设计了双管功率合成的方案。在HL-2A装置低杂波实验平台上,利用兆瓦级功率合成器,结合相位反馈技术,对两支高功率速调管、四路250kW进行相干微波功率合成,从而得到1MW LHCD微波。经过可行性分析得到,双管相位偏离15^o时合成效率下降约1.8%,幅度偏差10%时合成效率下降约0.1%。由此可得到双管功率合成技术的具体实施方案。     

The Design of the Microwave Exciter for Klystron

To carry out lower hybrid wave heating and current drive plasma experiment on tokamak, we need mega-watt order of microwave power generated by the parallel-running klystrons. Those klystrons must be driven by the microwave exciter. Now our microwave exciter is used for many years and its performance is decreased very much. It can not satisfy any more the hybrid wave heating and current drive plasma experiment. So we set out to design a new microwave exciter that is consist of the microwave solid components, amplitudestabilization control, modularization design with multitude-outputs, microwave phase control in order to satisfy the demand of the different work in the hybrid wave heating and current drive plasma experiment.     

高功率全光纤保偏主振荡功率放大型光纤激光器的实验研究

进行了全光纤保偏主振荡功率放大型光纤激光器的实验研究. 采用两级级联放大的方式, 利用纤芯为5 μupm 的小芯径双包层保偏光纤, 在最大抽运功率为88 W 时实现了67 W的1083 nm保偏激光输出, 纤芯内的激光功率密度约为3.4 W/μupm², 光-光转换效率为76%．分析结果表明, 进一步提高抽运功率有望获得更高功率的激光输出．     

Helical magnetocumulative generators with magnetic flux amplification: Comparative advantages of amplification schemes and the operational efficiency of generators with dynamic transformation

The amplification capabilities of two types of helical magnetocumulative generators based on the cascade scheme of magnetic flux amplification, generators with dynamic transformation, and those with transformer coupling between the cascades, are compared analytically and using numerical simulation. A tendency arising in real systems suffering from magnetic flux (energy) losses is studied. The reliability and efficiency of the generators with dynamic transformation can be improved by optimizing the operating modes of the generators and suppressing voltage surges, which are inherent in such devices and arise in the course of flux capture. A method to avoid voltage surges is proposed.