高增益相对论速调管放大器自激振荡机理及抑制技术研究

【作者】 陈永东；

【导师】 金晓； 李正红； 黄华；

【作者基本信息】 中国工程物理研究院 ， 无线电物理， 2013， 博士

【摘要】 高功率微波器件受其结构和功率容量的影响,其峰值功率受到限制。要实现更高的辐射功率,目前可行的技术路线是多台高功率微波器件的合成。由于相对论速调管放大器具有高增益、高功率以及相位和频率稳定的特点,因此强流相对论速调管放大器是目前实现该技术路线的优选微波器件之一,但这种器件在高增益条件下很容易产生自激振荡问题,严重影响器件的工作特性。论文基于一个四腔S波段强流高增益相对论速调管放大器进行了自激振荡产生机理及相关抑制技术的理论分析、粒子模拟和实验研究。论文根据单腔振荡和腔间耦合振荡的机理,(1)分析了单腔自激振荡的物理过程,并给出相对论速调管中各谐振腔的渡越角范围；(2)分析了腔间耦合导致自激振荡的物理过程,给出了高次模起振电流与器件结构参数之间的关系,并给出了提高起振电流抑制高次模产生的措施,该措施为：通过调节中间腔之间的漂移管长度(漂移管长度要同自激振荡模式谐振长度失配)、降低中间腔的Q值提高高次模起振电流和在漂移管中加载吸波材料截断高次模的传播途径来抑制自激振荡,从而实现腔间耦合的抑制,(3)通过PIC粒子模拟不仅验证了该措施的有效性,同时在kW注入微波条件下,模拟获得了增益大于60dB,功率3GW的高功率微波输出。关于强流相对论速调管放大器中回流电子问题,该问题主要涉及器件输出腔设计、注入微波功率和电子束等参数的优化,论文从四个方面进行研究：(1)从理论上推导出回流电子所受约束力的表达式,该式很好地解释了电子回流过程中容易发散的现象；(2)研究了回流电子产生的机理,给出了电子的回流与输出腔间隙电压、电子进入输出腔间隙时的初始相位和初始动能的关系；(3)分析了回流电子在末前腔引起自激振荡的回流电流强度和相位条件。(4)模拟分析了注入微波,电子束,器件结构等参数变化对电子回流的影响,给出了抑制回流电流引起的自激振荡的措施,即调节注入微波、腔体结构,电子束等等参数的控制回流电子强度,以及提高末前腔回流电流起振阈值抑制自己振荡,并在模拟中得到了验证。论文结合抑制自激振荡的措施,利用PIC程序完成了S波段3GW高增益强流RKA的模拟设计,在电子回流和腔间耦合自激振荡达到抑制的基础上,当注入微波2.3kW,电子束电压电流分别为1MV,12.5kA条件下模拟获得功率3GW,增益61dB,效率24%的稳定微波输出,同时将电子束参数900kW,8kA,1.3kW注入下获得2.05GW,效率28.5%,增益的RKA器件在LTD加速器平台开展了微波器件实验,(1)实验上验证了自激振荡抑制措施的有效性,(2)在注入微波功率为10kW级,电子束参数为900kV,7.8kA条件下,实验上获得GW级高功率微波输出,微波脉冲宽度为103ns,效率为26.5%,增益达到52dB。更多还原

【Abstract】 As the technology of structure process and power capacity of high-power microwave devices are restricted, the output power of a single device is quite close to its limitation. To achieve higher output power at present, a feasible way is the combination of several high-power microwave devices. Because intense relativistic klystron amplifier (1RKA) has characteristics of high gain, high power, locking of phase and frequency, it was used for power combination. However self-oscillation will seriously affect the device’s operating characteristics, espicially for the high gain cases. And the high gain devices need very lower rf input power to drive, so the technologhy pressure can be significantly decreased compared with the low gain cases. In order to accomplish a high gain (more than50dB) relativistics klystron ampilfier, an S-band1RKA with four cavities is chose to study self-oscillation mechanism and suppression technology through theory analyze, particle simulation and experimental research.The mechanism of monotron oscillation and couple between cavities are investigated for the suppression of the non-working modes’excitation as follows.(1) The physics mechanism of monotron oscillation is analyzed to give the transit angle’s range for each caviy in the sturture;(2) Another kind of self-oscillation is also analyzed base on the couple between cavities, and the relationships between starting current of oscillation and structure parameters are given. So some methods of suppression high mode oscillation to increase the starting current of oscillation (such as adjusting length of drift tube between idle cavities and decreasing Q value of idle cavities) are proposed.(3)the validity of supressing method are not only proved in PIC simulation, but also under the condition of2.3kW input microwave power, output microwave with power of3GW, efficiency of24%, gain of61dB is obtainedIn intense relativist]c klystron amplifier, the raltion between the returning electrons and the design of output cavity, the parameter of beam and inject microwave is given. Four aspects are studied:(1) the radial force expressions of returning electrons is deduced, which well explained the phenomena of returning electronic easily diffusing and intercepted by drift tube;(2) the generating mechanism of returning electrons is studied, the study shows that the electronic reflux is closely related to voltage of output cavity gap, electronic initial phase and electronic initial kinetic energy;(3)the condition of current intension and phase of returning electron which excite oscillation in the upstream cavities is ananlyzed;(4)through simulationt to study how parameters of structure, input microwave power and electron beam affect the electronic returning, and then propose some restraining methods, these retraining measures is validated in simulation,the study found that output microwave with higher power,higher gain, phase and frequency locking,and higher efficiency can not be attained untill comprehensive suppressing measures are adopted.According to the self-oscillation supressing method,an S-band3GW high gain IRKA is designed through PIC simulation,an output microwave with power of3GW,efficiency of24%,gain of61dB is obtained.(?) the (?) time,an experiment research of(?)(?)(?)with the input microwave powe the of10kW level,the high power microweive with bandwidth of103ns,effiency of26.5%,gain of52dBand GW level output power is obtained.更多还原