磁场对磁绝缘离子二极管性能的影响

基于等离子体的爆炸发射模型，用自洽的2—1／2维胞中粒子(PIC)模拟方法研究了磁场对强脉冲磁绝缘离子二极管性能的影响。给出了外加磁场为0—2Bcrit、二极管峰值电压为300kv情况下，二极管间隙中电子和质子的轨迹、二极管束流Id、阴极发射电子在阳极上损失的电子流密度je和在阴极引出质子束流密度jp随时间的演变过程。讨论了磁场对虚阴极、二极管阻抗和二极管能量转换效率等的影响。     

螺线管磁场旋转束流法测量Mini-LIA电子束能量

介绍了螺线管磁场旋转束流法的能量测量原理和在Mini-uA上开展的单脉冲电子束能量测量实验.通过测量束流在螺线管磁场中的旋转角度,得到Mini-LIA出口处电子束能量,与加速器总的加速电压符合得很好.分析了旋束法的测量误差和应用特点,给出了旋束法测量的适用范围.     

强流脉冲电子束加速器二极管的诊断触发问题

一、引言二极管是强流脉冲电子束加速器(REBA)的关键部件(见图1),粒子束的产生和聚焦是在二极管里完成的。二极管性能的研究主要依赖于对束流的诊断,而诊断包括电压、电流、束流能量、X射线辐射测量等等,通常要用多种方法对上述参量进行联合诊断,以互     

强流窄脉冲电子枪系统

该束流源利用铁氧体线强功率纳秒脉冲发生器驱动一支加栅皮尔斯枪。在阴极负高压值为82kV时,可得到幅值19A,宽度2.4ns的阳极输出窄脉冲电子束流。根据束流测试结果,文章简略讨论了电子极间渡越时间对束流及枪设计的影响。     

螺线管透镜像差导致的束流发射度增长研究

螺线管透镜常作为低能束流的聚焦元件,不可避免地具有像差,导致束流发射度增长,降低束流传输效率。本文通过理论推导和计算机模拟,给出了不同束流包络、不同磁感应强度和不同磁场形状的情况下束流经过实际透镜后的发射度增长。结果表明,发射度增长主要与束流包络和磁感应强度有关。但在一定范围内,优化磁场形状也能起到控制发射度增长的作用。     

四路并联二极管辐射X射线场参数计算

利用二极管的电压、电流计算了发射电子束能谱参数,建立了四路并联二极管阳极靶蒙特卡罗粒子输运计算模型,给出了辐射X射线场参数;将四路并联二极管的每个二极管划分为若干小单元,将其作为点源,采用数值积分的方法计算了辐射X射线剂量分布,并分析了空间不同位置处每路二极管对剂量的贡献。结果表明:真空中,距离四路并联二极管阳极靶5cm位置处,X射线注量为3.55mJ/cm2,光子平均能量为62.18keV,120keV以下的光子占辐射X射线谱总能量的81.84%,电子束转换效率为0.30%;在2 700cm2范围内,中轴线和对角线上的剂量均匀性分别为3.20和6.31;在2 000cm2范围内,中轴线和对角线上的剂量均匀性均小于2。     

激光驱动飞秒电子束消色差传输束线设计

激光等离子体加速输出的电子束具有fs量级脉冲长度的优异品质。由于强激光场的存在，直接应用存在一定困难，更多应用场景需要把电子束传输到应用端。能散导致电子束在传输中产生能量啁啾，需要通过束流光学设计抑制脉冲长度的增长。通过对电子束在消色差束线中传输的研究，探索了消色差和非消色差传输中脉冲长度压缩的差异，以及消色差束线中偏转角度、偏转半径对不同能量电子束脉冲长度压缩的影响。针对消色差传输中仅有某个能量电子束得到最优压缩的局限，利用四极透镜磁场梯度的调节使电子束的传输适度偏离消色差，改变对能量啁啾的影响，实现在固定尺寸束线中不同能量电子束的压缩。     

新型电子直线加速器测试与改进

一种新型的省略电子枪的小型直线加速器被研制成功。高功率速调管的用毕束流被引出作为注入电子,从而取代了传统的电子枪部分。装置在调试完成后开始运行,我们对获得加速后的电子束性能做了初步测量,并与模拟结果进行了对比。结果表明,加速器输出流强远低于设计目标。运用Parmela程序详细分析了电子束流损失的主要因素,针对减少束流损失,提高加速器输出流强,提出了新的改进方案。通过计算分析,得出了该方案良好的可行性。     

微秒矩形脉冲顶部抖动测量

一、导言速调管电压脉冲顶部的变化会引起微波输出相移,影响束特性。因此,电子直线加速器对调制器输出脉冲顶部平坦度提出严格要求。测量脉冲顶部特性的方法有多种。例如利用场致发射二极管测量高压矩形脉冲顶部电压的微小变化;利用Kerr效应测量高压脉冲绝对值及确定脉冲形状等。但这些方     

螺线管透镜聚焦特性

螺线管磁场透镜不可避免地具有球差,因此引起束流发射度增加。该文力图以多种方法改进磁场特性减少球差,计算表明增加磁场极间距离或将磁极头倒角都可以显著地减小球差系数。同时根据螺线管磁场沿轴磁场分布计算透镜的等效参数,它的大小仅与磁路形状有关,与磁场强度无关。     

电子回旋自共振加速器输出能量的影响因素及优化

回旋自共振加速器（CARA）加速效率高,在低能、大功率电子束领域具有非常好的应用前景。由于加速腔浸没在螺线管磁场中,电子束在轴向静态磁场的约束下螺旋前进,与加速腔中的TE₁₁模微波场保持同步而被横向持续加速。但加速器的输出能量并不随加速过程递增,而是与电子束的注入能量、轴向静态磁场、加速腔波导长度及微波场强度等多个相互约束的参数相关。本文从理论上分析了相关参数对输出能量的影响,利用三维电磁场仿真软件CST及粒子跟踪程序分别研究了相关参数对输出电子束状态的约束关系,并对这些参数进行联合优化,使得电子输出能量达到设计值。     

小型静态CT用多焦点X射线源电子束偏转系统研究

第5代全静态电子束CT（EBCT）能在被检测物体、射线源和探测器均处于静止状态下完成CT扫描成像。这种EBCT成像方式既可应用于粉体材料、生物活体样品等易形变物体的CT检测,又可应用于物流包裹、在役管线等的快速CT检测。高精度的电子束偏转系统是静态CT成像多焦点射线源的关键技术之一。本文基于麦克斯韦电磁场相互作用理论,探讨了电子束在均匀磁场、小偏转角、近轴区域内的散焦、畸变及灵敏度特性,研究了影响电子束扫描系统焦点位置重复精度的物理参数及电子束在靶平面上的扫描偏转量与偏转线圈电流的线性关系。并设计、加工制作了一种小型高精度多焦点X射线的电子束偏转扫描系统,实验采用直径0.1 mm标准针规电子束扫描DR投影图像序列,验证了电子束偏转系统有良好的偏转线性,偏转量正比于O点的磁场强度,而与电子束的位置等初始条件无关。实验通过电子束偏转系统控制电子束偏转扫描,获得了熔断式保险管（Ø100 μm）的250个 X 射线视角投影,完成了第5代全静态三维CT重建图像。     

Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

The method of energy dispersion in magnetic field is used to analyze the energy spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator.A sector magnet is applied for energy analysis of the electron beam,with a bending radius of 300 mm and a deflection angle of 90°.For each pulse,the time-resolved and integral images of the electron position at the output port of beam-bending line are recorded by a streak camera and a CCD camera,respectively.Experimental results demonstrate an energy spread of less than ±2.0%for the electron pulses.The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.     

Beam dynamics design of an SP-FEL compact THz source

In recent years, people are looking for a new compact THz source with high emission power, one potential choice is to build small accelerator with Smith-Purcell radiation. The main difficulty is how to obtain high quality electron beam. In this paper, the beam dynamics design of a compact THz source is presented. The electron beam is produced by an electron gun and compressed by permanent magnets. The electron gun is similar to the Shanghai EBIT,but permanent magnets are used, instead of the superconducting magnets in Shanghai EBIT. With this design, we can reduce the size and cost of the whole device. Poisson/Pandira was employed to simulate and optimize the magnetic field. Egun was used to simulate the beam trajectories from the electron gun to the collector. Within 2 centimeters around the center of longitudinal magnetic field, the calculation showed that the beam satisfies to our design aim.     

The influence of magnetic field on the beam quality of relativistic electron beam long-range propagation in near-Earth environment

In recent years,it has been proposed to use satellite-mounted radio-frequency(RF)accelerators to produce high-current relativistic electron beams to complete debris removal tasks.However,when simulating the long-range propagation(km-range)process of the electron beam,it is difficult to directly use the particle-in-cell method to simultaneously consider the space charge effect of beam and the influence of the geomagnetic field.Owing to these limitations,in this paper,we proposed a simplified method.The ps-range electronic micropulses emitted by the RF accelerator were transmitted and fused to form a ns-range electron beam;then,combined with the improved moving window technology,the model was constructed to simulate the long-range propagation process of the relativistic electron beam in near-Earth environment.Finally,by setting the direction of movement of the beam to be parallel,perpendicular and at an inclination of 3° to the magnetic field,we analyzed and compared the effects of the applied magnetic fields in different directions on the quality of the beam during long-range propagation.The simulation results showed that the parallel state of the beam motion and magnetic fields should be achieved as much as possible to ensure the feasibility of the space debris removal.     

强流相对论电子束传输过程中的电荷中和理论

讨论了有外加磁场情况下,强流相对论电子束传输过程中的电荷中和理论,着重讨论了二次电子逃逸时间和外加磁场对空间电荷中和的影响。得知当电子束半径大于2.0 cm 时,在计算空间电荷中和时间时就得考虑二次电子逃逸时间的影响。在一定条件下,外加磁场对空间电荷中和有阻碍作用,对于长漂移室,存在空间电荷中和允许的磁感应强度上限。     

Design and Experimental Demonstration of a 94-GHz Gyrotron with Complex Cavity Operating at the Second Harmonic

A systematic theoretical and experimental study on 94-GHz second-harmonic gyrotron with a superconducting magnet system is presented in this paper. A complex cavity with gradual transition is employed in the gyrotron. A self-consistent field nonlinear theory is used and numerical simulation results for electron beam interaction with TE₀₂–TE₀₃ modes are given. A pulse output power of 235.2 kW is obtained by simulation at a beam voltage of 60 kV with beam current of 10 A and magnetic field 17 kG, corresponding to an efficiency of 39.2 %.     

环形电子束在周期永磁场中传输的理论研究

通过对环形电子束中电子的受力分析，得出了在周期永磁场(PPM)中电子束传输的条件和电子束的形状。研究认为可以使用PPM对环形电子束进行传输。     

Relativistic Magnetron Performance Improvement Through Simultaneous Electric and Magnetic Fields Priming

A three dimensional particle-in-cell code MAGIC-3D has been used to study the output performance improvement of a relativistic magnetron through simultaneous use of electric priming and magnetic field perturbation techniques. The side resonators of the resonant structure have been loaded symmetrically at angle of 120° with low-loss annular shaped dielectric to implement the electric field priming alternating with metal rods to perturb the RF magnetic field. All the simulations have been performed on the well known A6 relativistic magnetron for 2π-mode of operation. The results indicate that single 2π-mode operation with 30 % reduction in startup time and 12 % improvement in radiated output power can be achieved through electric priming by loading the RF resonators with annular shaped low-loss dielectric and magnetic field perturbation with 3-metal rods.     

强流束晕-混沌的模糊逻辑控制研究

以周期性磁场聚焦传输通道中的K-V(Kapchinskij-Vladimirskij)分布离子束为例,引入带偏置的升余弦函数近似刻画实际磁场,理论分析了通道中强流离子束的束晕-混沌动力学行为。针对束晕-混沌的控制问题,提出了束晕-混沌的模糊逻辑控制方法。模糊控制器采用Mamdani推理系统,其输出作为控制因子线性调整外部磁场强度。用模糊相平面法分析了控制系统的稳定性。仿真结果显示：在控制条件下,混沌变化的束包络半径被稳定控制;将该方法应用于多粒子模型,消除了束晕及其再生现象,束的品质获得较大提高。该模糊控制方法具有不依赖束输运数学模型、控制器简单、磁场调节呈线性关系、易于工程实现等优点。