Multipacting saturation in parallel plate and micro-pulse electron gun

A novel parallel plate model is proposed that divides the electron cloud into three parts at saturation,and it is studied in detail using both an analytical approach and particle-in-cell(PIC) code simulations. As one part of the electron cloud, ribbons modes are suggested by tracking the trajectory of individual particles, and the aim of this mode form is to simplify the progress of the multipacting effect in the parallel plate so as to be eliminated by optimizing RF parameters. The micro-pulse electron gun(MPG) has demonstrated the potential to address the need for high peak and average current electron beams, hence studying the multipacting in MPG is essential. On the basis of studying multipacting in the parallel plate, it is clear that increasing the cavity voltage is of interest in yielding high quality beams in the gun.     

Beam tail effect of a performance-enhanced EC-ITC RF gun

The beam tail effect of multi-bunches will influence the electron beam performance in a high intensity thermionic RF gun. Beam dynamic calculations that illustrate the working states of single beam tail and multi-pulse feed-in of a performance-enhanced EC-ITC （external cathode independent tunable cavity） RF gun for an FEL （free electron laser） injector are performed to estimate the extracted bunch properties. By using both Parmela and homemade MATLAB codes, the effects of a single beam tail as well as interactions of multi-pulses are analyzed, where a ring-based electron algorithm is adopted to calculated RF fields and the space-charge field. Furthermore, the procedure of unexpected deviated-energy particles mixed with an effective bunch head is described by the MATLAB code as well. As a result, the performance-enhanced EC-ITC RF gun is proved to have the capability to extract continual stable bunches suitable for a high requirement THz-FEL.     

Electron gun system for NSC KIPT linac

In the NSC KIPT linac, a neutron source based on a subcritical assembly driven by a 100 MeV/100 kW electron linear accelerator is under design and development. The linear accelerator needs a new high current electron gun. In this paper, the physical design, mechanical fabrication and beam test of this new electron gun are described.The emission current is designed to be higher than 2 A for the pulse width of 3 μs with repetition rate of 50 Hz.The gun will operate with a DC high voltage power supply that can provide a high voltage up to 150 kV. Computer simulations and optimizations have been carried out in the design stage, including the gun geometry and beam transport line. The test results of high voltage conditioning and beam test are presented. The operation status of the electron gun system is also included. The basic test results show that the design, manufacture, and operation of the new electron system are basically successful.     

Design of a new compact THz source based on Smith-Purcell radiation

In recent years, people are dedicated to the research work of finding compact THz sources with high emission power. Smith-Purcell radiation is qualified for the possibility of coherent enhancement due to the effect of FEL mechanism. The compact experiment device is expected to produce hundreds mW level THz ray. The electron beam with good quality is provided under the optimized design of the electron gun. Besides, the grating is designed as an oscillator without any external feedbacks. While the beam passes through the grating surface, the beam bunching will be strong and the second harmonics enhancement will be evident, as is seen from the simulation results.     

Design of a new compact THz source based on Smith-Purcell radiation

In recent years, people are dedicated to the research work of finding compact THz sources with high emission power. Smith-Purcell radiation is qualified for the possibility of coherent enhancement due to the effect of FEL mechanism. The compact experiment device is expected to produce hundreds mW level THz ray. The electron beam with good quality is provided under the optimized design of the electron gun. Besides, the grating is designed as an oscillator without any external feedbacks. While the beam passes through the grating surface, the beam bunching will be strong and the second harmonics enhancement will be evident, as is seen from the simulation results.     

BXERL photo-injector based on a 217 MHz normal conducting RF gun

The Beijing X-ray Energy Recovery Linac (BXERL) test facility is proposed in Institute of High Physics (IHEP). In this proposal, the main linac requires the injector to provide an electron beam with 5 MeV energy and 10 mA average current. An injector based on DC gun technology is the first candidate electron source for BXERL. However, the field emission in the DC gun cavity makes it much more difficult to increase the high voltage to more than 500 kV. Another technology based on a 217 MHz normal conducting RF gun is proposed as the backup injector for this test facility. We have designed this RF gun with 2D SUPERFISH code and 3D MICROWAVE STUDIO code. In this paper, we present the optimized design of the gun cavity, the gun RF parameters and the set-up of the whole injector system. The detailed beam dynamics have been done and the simulation results show that the injector can generate electron bunches with RMS normalized emittance 1.0 uppi mmcdotmrad, bunch length 0.77 mm, beam energy 5.0 MeV and energy spread 0.60%.     

HIRFL—CSR实验环电子冷却装置调试

HIRFL-CSR实验环电子冷却装置采用了能够产生空心电子束的电子枪。弯曲螺线管内采用了静电偏转电极，冷却段采用了独立的高精度螺线管串联产生纵向磁场的设计。测量了沿离子束运动方向冷却段磁场分布及磁场平行度、电子枪和收集器性能、300kV高压电源相关参数。结果表明，此装置达到了预期的设计目标。: In CSRe electron cooling device， a special electron gun which can produce variable profile electron beam with different size and density distribution was adopted for decreasing ion losses. Electrostatic bending device was used for reducing electron beam losses and improving vacuum condition. The instability of the electron beam is suppressed because the secondary electrons from collector would come back to the collector in the same orbit finally. Longitudinal magnetic field with parallelism better than 10-4 was achieved by adopting of independent high precise solenoid coils at cooling section. In this case， the r.m.s deviations of the transverse magnetic field at cooling section in horizontal and vertical direction are 3.298×10-5 and 2.458×10-5 respectively. The characters of the gun and collector were investigated. The results were presented and indicate that it achieves the design purpose very well.     

Multipacting analysis in micro-pulse electron gun

Modeling multipacting to steady state saturation is of interest in determining the performance of the micro-pulse electron gun. In this paper, a novel method is proposed to calculate the multipacting resonance param- eters for the gun. This method works well, and the 2-D simulation results suggest that steady state saturation can be achieved in the gun. After saturation the transition from two-surface multipacting to single-surface multipacting occurred, and an extensive range of electron emission time is a suggested way to avoid this kind of transition.     

Theoretical research on electron beam modulation in a field-emission cold cathode electron gun

In order to develop miniaturized and integrated electron vacuum devices, the electron beam modulation in a field- emission （FE） electron gun based on carbon nanotubes is researched. By feeding a high-frequency field between the cathode and the anode, the steady FE electron beam can be modulated in the electron gun. The optimal structure of the electron gun is discovered using 3D electromagnetism simulation software, and the FE electron gun is simulated by PIC simulation software. The results show that a broadband （74-114 GHz） modulation can be achieved by the electron gun with a rhombus channel, and the modulation amplitude of the beam current increases with the increases in the input power and the electrostatic field.     

First Beam Measurements of the S-Band photocathode Radio-Frequency Gun at Tsinghua University

During the last decades, photocathode rf gun has been proven to be successful in generating the high brightness electron beam （-lnC,-lπ mmmrad,-l ps） which is required by the ILC, XFEL, Thomson scattering x-ra y source, etc. A photocathode rf gun system is built to develop electron source for the Thomson scattering x-ray source at Accelerator Laboratory of Tsinghua University. The system consists of a BNL/ATF-type 1.6 cell S-band rf cavity, a solenoid for emittance compensation, a laser system and some simple equipments for beam diagnosis. The first beam measurements of the photocathode rf gun, including the dark current, transverse beam profile, charge and quantum efficiency, are reported.     

毫米波回旋速调管磁控注入电子枪模拟计算

介绍了毫米波回旋速调管磁控注入电子枪的结构与特点。电子枪提供的电子束流性能直接影响到回旋速调管的总体参数，为保证整管的效率和输出功率，利用电子枪模拟程序对电子轨迹进行模拟计算，研究了电极形状、磁场分布以及电子轨迹与电子注参量的影响，并为磁控注入电子枪的设计提供了理论依据。     

部分屏蔽多极电子鎗聚焦问题

本文对于在有磁场下多阳极电子鎗的电子注聚焦问题进行了理论分析。阴极处磁场可以具有任意屏蔽程度,得到了在加速场内描写电子轨迹的傍轴方程的解析解。在理论分析中,考虑了包括空间电荷效应的情况。     

回旋管双阳极磁控注入电子枪的设计

根据回旋管对电子枪的要求,设计了该双阳极磁控注入电子枪。给出了电极形状、电子轨迹与电子注参量。这种电子枪具有速度零散小、层流性较好、体积小等特点。     

回旋管双阳极磁控注入电子枪的设计

 根据回旋管对电子枪的要求,设计了该双阳极磁控注入电子枪。给出了电极形状、电子轨迹与电子注参量。这种电子枪具有速度零散小、层流性较好、体积小等特点。     

回旋管单阳极电子枪计算机辅助设计

 根据回旋管对电子枪的要求，采用综合法和分析法设计了该单阳极磁控注入电子枪。编制了一套大型的计算程序，利用计算机辅助设计，给出了电极形状、电子轨迹与电子注参量。计算表明，这种电子枪具有速度零散小、层流性较好、体积小等特点。该枪已用于制管实验中。由热测实验表明，它具有明显的优点，并获得了127kW的峰值功率和超过10%的效率。     

多腔微波电子枪聚束腔作用分析

 分析了聚束腔中电场分布及电子的运动过程,使用RUNGE KUTTA法求出不同腔长时电子的俘获相位及不同初始相位电子的运动轨迹,讨论了加聚束段对减小电子反轰的作用。研制的4+1/2腔RF-gun使用首腔和第二加速腔作为聚束段,取得了高占空因子,较高束流功率的实验结果。     

An Iron-Free Magnetron-Injection-Gun for a 28GHz, 200kW Gyroklystron Amplifier

A design study of a double-anode magnetron-injection-gun is performed to incorporate the electron gun into a high power 28GHz gyroklystron amplifier operating at 70kV and 8.2A. The electron gun is designed to be used in a tapered magnetic field in the cathode region produced from an iron-free superconducting magnet. An electron trajectory code predicts a beam axial velocity spread of 5.9% at = 1.5, 70kV, 8.2A and 10.4kG, which is a high quality electron beam suitable for the high gain, high efficiency, five-cavity gyroklystron amplifier. The successful design of the high quality electron gun is attributed to a longer gap between the modulating anode and the grounded anode compared with the case of the first 28GHz electron gun built with an iron enclosed electromagnet.     

微束斑X射线源LaB_6阴极电子枪的设计

LaB6阴极电子枪是微束斑X射线源的关键组成部件之一。详细的讨论了电子枪的各组成电极 ,即LaB6阴极、Wehnelt栅极和阳极的设计。采用边界元法 (BEM )对电子枪内部电场电位和场强分布进行了有效的数值计算 ,并从阴极开始起利用四阶Runge Kutta法追踪电子的运动轨迹。给出了当阳极端口处电子束半径为设计值时各电极电压、电极结构等工作参量 ,利用该LaB6阴极电子枪可以满足微束斑X射线源需要高亮度、微细电子束发射的要求。     

单阳极磁控注入电子枪的设计

 该单阳极磁控注入电子枪是为8mm永磁包装回旋振荡管设计的。首先利用绝热理论和角动量守恒理论进行了初始的电极参数设计,其次讨论和选取数值计算方法,然后利用自编的程序进行数值计算和优化,同时讨论了空间电荷的影响和速度零散的改善,最终得到最佳的电极和电子注参数。该电子枪已经应用于制管实验中。     

A new approach for evaluating the current and charge density distributions in electron guns and beams

Current and space-charge density distribution calculation is of great significance for numerical analysis and design of high-current electron guns and beams. When the electrons’ thermal initial velocities are taken into account, though there have been some numerical methods published, the calculation is very complicated. By introducing equivalent meridional potential and projection trajectory theory, the curvilinear axis trajectory equation for electrons neighboring to a central curved trajectory in rotationally symmetric electro-magnetic fields is derived in first- and second-order approximations. The evolution equation of the current density distribution of toroidal electron sub-beams is derived and it can be used to calculate the current and charge density distribution in electron beams and guns in iteration calculation. A compact numerical algorithm for calculating round high-current electron guns and beams was developed and related program was written as well. As examples, the evolution of the current density distribution of a Pierce gun and a periodic magnetic focusing high-current electron beam is simulated. This proves that this method is effective and practical.