激光参数影响太赫兹辐射的数值模拟

 利用2维PIC程序模拟了聚焦激光脉冲垂直入射非均匀等离子体,在界面激发超强太赫兹辐射的物理过程,研究了激光强度、脉宽和焦斑半径对太赫兹辐射功率和频率的影响,并和模式转换理论作了对比。结果表明:激光强度是影响太赫兹辐射功率的主要因素;当脉宽在等离子体波长附近时,激起的静电波振幅最大,此时对应的太赫兹辐射最强;同时存在一个最优的焦斑半径,使得辐射功率最大。     

Theoretical and Numerical Investigation of a Four-cavity TE021-Mode Gyroklystron

Using self-consistent field theory and PIC simulation, the interaction of electron flow with HF fields in a four-cavity Gyroklystron with TE₀₂₁-mode has been analyzed. Self-consistent field theory includes both linear theory and nonlinear theory. Optimized parameters and their corresponding efficiency, gain and bandwidth of the optimized Gyroklystron have been found. Numerical investigation using PIC simulation is also given. Parameters of the cavities which are operating in TE₀₂₁ mode are optimized to minimize TE₀₁₁ mode and to suppress parasitic self-oscillations. The results of theory are in good qualitative agreement with PIC simulation. This work is supported by the Chinese Natural Science Foundation under Contract 60532     

毫米波段高功率绕射辐射振荡器的研究

提出采用大口径、浅褶皱和短周期分段式慢波结构作为高功率毫米波绕射辐射振荡器的高频系统。采用通用理论对器件的色散特性进行了分析,用PIC方法对整体器件进行了模拟。在此基础上,开展了实验研究工作,测试了器件输出微波功率和频率。初步实验结果与理论分析和PIC模拟结果的趋势基本吻合。     

毫米波段高功率绕射辐射振荡器的研究

 提出采用大口径、浅褶皱和短周期分段式慢波结构作为高功率毫米波绕射辐射振荡器的高频系统。采用通用理论对器件的色散特性进行了分析,用PIC方法对整体器件进行了模拟。在此基础上,开展了实验研究工作,测试了器件输出微波功率和频率。初步实验结果与理论分析和PIC模拟结果的趋势基本吻合。     

向内发射同轴虚阴极振荡器波束互作用的数值模拟研究

对向内发射同轴虚阴极振荡器微波主频进行了解析求解, 利用稳态相对论流体Maxwell方程组得到了微波主频所满足的方程; 同时使用MAFIA程序的TS3模块对向内发射同轴虚阴极振荡器中波束互作用进行了全三维PIC数值模拟研究, 通过对微波输出圆波导中5个传输模式的监测,得到了各模式的频谱分布及输出功率. 结果表明, 在有阳极反射板存在时, 构成的准腔结构能够有效地改善频谱, 从而提高能量转换效率.     

Raman-assisted parametric frequency conversion in a normally dispersive single-mode fiber

We demonstrate efficient frequency conversion with large frequency shifts of an anti-Stokes signal into a parametrically seeded Stokes idler, which is generated by a highly mismatched three-wave mixing interaction and subsequent Raman amplification in a normally dispersive single-mode fiber. The use of non-phase-matched waves in Raman-assisted three-wave mixing interactions overcomes the strict spectral limitations imposed by phase-matching conditions in parametric frequency-conversion processes.     

Study of a rectangular coupled cavity extendedinteraction oscillator in sub-terahertz waves

An extended interaction oscillator （EIO） generating 120 GHz wave in sub-terahertz waves is studied by using the three-dimensional electromagnetic simulation software CST and PIC codes. A rectangular reentrant coupled-cavity is proposed as the slow-wave structure of EIO. By CST, the circuit parameters including frequency-phase dispersion, interaction impedance and characteristic impedance are simulated and calculated. The operation mode of EIO is chosen very close to the point where βL = 2π with corresponding frequency 120 GHz, the beam voltage 12 kV and the dimensions of the cavity with the period 0.5mm, the height 3mm and the width 1.4mm. Simulation results of beam-wave interaction by PIC show that the exciting frequency is 120.85 GHz and output peak power 465 W with 12-period coupled-cavity with the perveance 0.17 μP. Simulation results indicate that the EIO has very wide range of the operation voltage.     

一种高功率返波管理论

对一种热阴极高功率返波管进行了理论研究,其具有寿命长稳定性好的特点。采用的热阴极发射电流密度为20 A/cm2,发射面积为100 cm2,发射总电流为2 kA。首先对该热阴极单阳极电子枪进行仿真研究,在确保不打火的情况下获得电子枪优化设计参数,再对整管进行粒子模拟研究,仿真结果表明,在工作频率为10.5 GHz时,该热阴极返波管的输出功率可以达到290 MW,换能效率为29%。     

一种高功率返波管理论

对一种热阴极高功率返波管进行了理论研究,其具有寿命长稳定性好的特点。采用的热阴极发射电流密度为20 A/cm2,发射面积为100 cm2,发射总电流为2 kA。首先对该热阴极单阳极电子枪进行仿真研究,在确保不打火的情况下获得电子枪优化设计参数,再对整管进行粒子模拟研究,仿真结果表明,在工作频率为10.5 GHz时,该热阴极返波管的输出功率可以达到290 MW,换能效率为29%。     

时频分布技术在激光与等离子体相互作用粒子模拟诊断中的应用

在对超短超强激光与等离子体相互作用进行粒子模拟诊断的研究中,输出量普遍为时间或空间上的非平稳信号。将时频分布技术引入粒子模拟结果的诊断,指出用时频分布技术等现代信号处理技术诊断模拟结果中的非平稳信号具有重要意义。作为实例,考察了用线性啁啾激光打靶条件下,包含nc/4(nc为等离子体临界密度）的非均匀等离子体区域中的受激拉曼散射的演化,并用时频分布技术得到了清晰的物理图像。     

Interaction of pulsed laser beams in quadratic nonlinear media

A theory of three-wave cascade interaction of pulsed laser beams in quadratic nonlinear media is developed with regard to diffraction and dispersion. The space-time trajectories of signal motion in a medium with an inhomogeneity induced by high-power low-frequency pumping are analyzed. It is shown that total signal reflection from a moving localized inhomogeneity can be implemented. This reflection is accompanied by a change in the frequency, velocity, and propagation direction of the signal wave.     

220 GHz回旋单腔管的设计

根据回旋管的线性理论和回旋管自洽非线性理论设计出工作频率为220 GHz,工作电压为20 kV,工作电流为2 A的回旋单腔振荡管,采用的工作模式为TE03模。利用粒子模拟软件MAGIC对设计方案进行验证,得到的注波互作用效率达到37%,平均输出功率为15 kW。     

一种新的高功率微波折叠式谐振腔径向速调管振荡器

提出一种高功率微波折叠式谐振腔径向速调管振荡器,用电子与电磁场相互作用的一维单电子模型分析了这种折叠式谐振腔径向速调管振荡器的特点。其特点为：径向尺寸小,起振电流低。用二维半PIC程序对折叠式谐振腔径向速调管振荡器进行数值模拟研究。结果表明,当二极管电压为380kV,电流为18kA时,输出微波功率峰值为1GW,主要微波频率为1.52GHz,输出微波为多频率成分微波。通过折叠式谐振腔的电子束得到很强的调制。     

基于Tesla变压器和螺旋线的长脉冲发生器

提出了一种结构紧凑的长脉冲发生器，该发生器的螺旋型形成线包含有磁性材料构成的内导体棒和外屏蔽。形成线通过内置的高耦合Tesla变压器充电，变压器的初级线圈紧靠外磁芯导体，次级线圈位于螺旋中筒和外筒之间。对这种结构的螺旋线进行了特征参数的理论计算和波传输数值模拟，并进行了简单的原理验证实验。实验结果表明:这种设计是合理的、可行的。     

一种新的高功率微波折叠式谐振腔径向速调管振荡器

 提出一种高功率微波折叠式谐振腔径向速调管振荡器，用电子与电磁场相互作用的一维单电子模型分析了这种折叠式谐振腔径向速调管振荡器的特点。其特点为：径向尺寸小，起振电流低。用二维半PIC程序对折叠式谐振腔径向速调管振荡器进行数值模拟研究。结果表明，当二极管电压为380kV，电流为18kA时，输出微波功率峰值为1GW，主要微波频率为1.52GHz，输出微波为多频率成分微波。通过折叠式谐振腔的电子束得到很强的调制。     

Quasi-universality and scaling behaviour of three-wave X-ray interference in crystals: A novel way for the quantitative determination of X-ray reflection phases

A quasi-universal function describing the intensity distribution of three-wave X-ray interaction in single crystals is derived for the first time from X-ray dynamical theory under the Bethe approximation for inversion-symmetry related reflections. The intensity distributions of three-wave interference can be scaled down to this dimensionless universal function with proper scaling factors. A newly derived intensity-ratio formula provides a new way of analyzing three-wave diffraction data for direct quantitative determination of X-ray reflection phases of complex systems involving macromolecules.     

Ka波段带状注相对论扩展互作用速调管放大器的分析与设计

带状注相对论扩展互作用速调管放大器是一种高功率、高频率的微波毫米波放大型器件, 具有广阔的应用前景. 本文分析了扩展互作用结构多间隙谐振腔的渡越时间效应, 推导了2π模场情况下谐振腔的能量交换系数和电子负载电导, 且通过计算表明工作在2π模式三间隙腔的电子负载电导是单间隙腔的9倍左右, 多间隙结构有利于提高器件效率. 利用三维粒子仿真软件, 对工作在Ka波段的带状注相对论扩展互作用速调管放大器进行了模拟研究, 采用宽高比为30:1的带状电子束以降低空间电荷效应, 在电子束电压为500 kV, 束流为1 kA, 轴向引导磁感应强度为0.8 T的情况下, 器件输出微波功率为190 MW, 频率为40 GHz, 器件效率为38%, 器件增益为69 dB.     

同轴波纹返波管色散特性研究及粒子模拟

 计算了同轴波纹慢波结构的色散特性,分析了波纹周期长度、波纹幅值大小以及同轴内导体半径对慢波结构色散特性的影响。研究表明内导体的存在使系统截止频率升高,系统尺寸可比普通波纹波导慢波系统更大, 并且可以采用大半径电子注并工作在低磁场状态。运用Magic软件对同轴波纹返波管进行了数值模拟, 发现同轴波导内场分布有利于注波互作用,在数值模拟基础上设计出高效率、低磁场的非均匀同轴波纹返波管,互作用效率达60%,聚束磁场小于1 T。     

Modeling and experimental studies of a side band power re-injection locked magnetron

A side band power re-injection locked(SBPRIL) magnetron is presented in this paper. A tuning stub is placed between the external injection locked(EIL) magnetron and the circulator. Side band power of the EIL magnetron is reflected back to the magnetron. The reflected side band power is reused and pulled back to the central frequency. A phase-locking model is developed from circuit theory to explain the process of reuse of side band power in SBPRIL magnetron. Theoretical analysis proves that the side band power is pulled back to the central frequency of the SBPRIL magnetron, then the amplitude of the RF voltage increases and the phase noise performance is improved. Particle-in-cell(PIC) simulation of a 10-vane continuous wave(CW) magnetron model is presented. Computer simulation predicts that the frequency spectrum's peak of the SBPRIL magnetron has an increase of 3.25 d B compared with the free running magnetron. The phase noise performance at the side band offset reduces 12.05 d B for the SBPRIL magnetron. Besides, the SBPRIL magnetron experiment is presented. Experimental results show that the spectrum peak rises by 14.29% for SBPRIL magnetron compared with the free running magnetron. The phase noise reduces more than 25 d B at 45-k Hz offset compared with the free running magnetron.     

S波段宽带大功率连续波耦合腔行波管3维模拟设计

使用3维PIC粒子模拟软件定量分析了耦合腔行波管的大信号注波互作用行为。使用完整的仿真模型完成了S波段连续波管型的设计,达到如下设计指标：工作频率2.0~2.3 GHz,输出功率4.3 kW,频带内增益波动±0.7 dB。提出了使用大介电常数微扰介质棒减小耦合阻抗计算误差的方法,研究了行波管的冷腔特性,给出了色散、耦合阻抗等参数。