Beam and image experiment of beam deflection electron gun for distributed X-ray sources

Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.

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.

Constructions and Preliminary HV Conditioning of a Photocathode Direct-Current Electron Gun at IHEP

As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address the technical challenges of producing very low ernittance beams at high average current. Construction of the dc gun is completed and a preliminary high voltage conditioning is carried out up to 440 k V. The design, construction and preliminary HV conditioning results for the dc gun are described.

Development and simulation of a gridded thermionic cathode electron gun for a high-energy photon source

A gridded thermionic cathode electron gun was developed for the linear accelerator of the High Energy Photon Source(HEPS).An electron gun should provide a large maximum bunch charge with a wide adjustable range.To satisfy these requirements,the shape of the electrode was optimized using a multi-objective genetic algorithm.A large bunch charge with an adjustable range was achieved using the grid-limited gun,the flow of which was analyzed using 3-D simulations.The electron gun has been manufactured and tested,and the measured data of the grid-limited current and simulation results are compared and discussed in this study.

The Use of an Electron Microchannel as a Self-Extracting and Focusing Plasma Cathode Electron Gun

A new and simple type of electron gun is presented.Unlike conventional electron guns,which require a heated filament or extractor,accelerator and focusing electrodes,this gun uses the collimated electron microchannels of an inertial electrostatic confinement（IEC） discharge to achieve the same outcome.A cylindrical cathode is placed coaxially within a cylindrical anode to create the discharge.Collimated beams of electrons and fast neutrals emerge along the axis of the cylindrical cathode.This geometry isolates one of the microchannels that emerge in a negatively biased IEC grid.The internal operating pressure range of the gun is 35-190 m Torr.A small aperture separates the gun from the main vacuum chamber in order to achieve a pressure differential.The chamber was operated at pressures of 4-12 m Torr.The measured current produced by the gun was 0.1-3 m A（0.2-14 m A corrected measurement） for discharge currents of 1-45 m A and discharge voltages of 0.5-12 k V.The collimated electron beam emerges from the aperture into the vacuum chamber.The performance of the gun is unaffected by the pressure differential between the vacuum chamber and the gun.This allows the aperture to be removed and the chamber pressure to be equal to the gun pressure if required.

Fuzzy identification of T-S model for beam stability control for electron gun

In this paper, Takagi-Sugeno(T-S) fuzzy control is proposed for stabilizing the output beam of accelerators. To model the nonlinear system, we proposed a hybrid optimization algorithm based on quantum-inspired differential evolution and genetic algorithm. Based on the T-S model identified, the corresponding statefeedback fuzzy controller is designed. The method is applied to the La B6 electron gun system in the industrial radiation accelerator and the simulation results show its effectiveness.

Development of a high current short pulse electron gun

Dielectric wall accelerator(DWA), towards high gradient acceleration field(30 MeV/m–100 MeV/m), is under development at Institute of Modern Physics. A prototype was designed and constructed to prove the principle. This needs a short pulse high current electron source to match the acceleration field generated by the Blumlein-type pulse forming lines(PFLs). In this paper, we report the design and test of a new type short pulse high current electron gun based on principle of vacuum arc discharge. Electron beams of 100 mA with pulse width of 10 ns were obtained.

Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches

This paper presents a method of generating terahertz （THz） coherent transition radiation （CTR） from picosecond ultrashort electron bunches including single and train bunches, which are produced by a photocathode radio frequency gun. The radiation characteristics of THz CTR including formation factor and energy spectrum are analysed in detail. With the help of a 2-dimensional particle-in-cell simulation, the radiation characteristics including power, energy and magnetic field are analysed. The results show that the radiation frequency can be adjusted by tuning the repetition frequency of the train bunch and the energy can be enhanced with the train bunches.

Performance of an electron linear accelerator for the first photoneutron source in China

A compact 15.0-MeV, 1.5-kW electron linear accelerator(LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai,China. This LINAC consists of five main parts: a thermal cathode grid-controlled electron gun, a pre-buncher, a variable-phase-velocity buncher, a light-speed accelerating structure, and a high-power transportation beamline. A digital feedforward radio frequency compensator is adopted to reduce the energy spread caused by the transient beam loading effect. Furthermore, a real-time electron gun emission feedback algorithm is used to keep the beam stable. After months of efforts, all the beam parameters successfully met the requirements of the facility. In this paper, the beam commissioning process and performance of the LINAC are presented.

RECENT PROGRESS IN MULTI-BEAM KLYSTRON IN IECAS

Recent research progresses in Multi-Beam Klystron (MBK) in IECAS are briefly introduced in the letter. The S-band MBKs of IECAS have peak power of 120-250 kW, average power of 4-9 kW, efficiency of 35-45%, gain of 41-46 dB, beam voltage of 15-19 kV, and weight of 40-45 kg. Some key technical problems of MBK are also described and discussed. Among them,improving the design of MBK to obtain the required bandwidth, raising beam transmission to increase average power, eliminating oscillation and spray spectrum, overcoming window breakdown caused by magic mode, reducing breakdown times of electrongun, are most important things for the practical MBK. Besides, further research work in MBK in IECAS is commented.

Special Technologies Related to Electron Beam Welding

In order to improve the manufacturing quality of electron beam welding,some technologies are developed by using the special features of electron beam.Comparing with the conventional electron beam welding,the usage of multi-beam technology and micro-beam technology are introduced.In addition.the development of beam diagnostic system is also presented.

小型化Ka波段行波管快启电子枪研究

针对弹载环境中毫米波行波管快速启动要求,利用ANSYS软件模拟电子枪阴极施加热丝功率对阴极温度产生的影响,并通过电子枪温度试验,定量测定热丝功率和阴极温度的对应关系,验证温度对阴极发射的影响。在模拟和试验基础上,开展电子枪小型化结构设计,成功研制出小型化毫米波弹载行波管用电子枪,使其满足弹载环境15 s快启功能。

用于超快扫描电子显微镜的光发射电子枪及电子光学模拟

超快扫描电子显微镜将泵浦探测技术与显微成像相结合,能够实现高时空分辨率下光诱导表面电荷动力学的可视化研究,对于半导体表面态以及光电器件的高分辨检测具有非常重要的意义.本文基于首台全国产化超快扫描电子显微镜的研制工作,阐述了将热发射电子枪改造成光发射电子枪后的参数化设计,定量分析了偏压,阴极、韦氏极、阳极的空间位置与交叉点位置、大小、发散角的依赖关系.分析结果显示,当韦氏极与阳极位置从8 mm调整到23 mm后,通过将灯丝深度从0.65 mm调整至0.45 mm,配合偏压调节可以实现热发射高分辨成像、低工作电压以及光发射的正常使用.此外,也分析了反射镜分布对电子光路的影响,发现当阳极高出反射镜1.4 mm后,图像畸变几乎消失.还研究了偏置电压对脉冲光电子在时域上的影响,结果表明随着偏压的增大,光发射的时间零点会推后且时间展宽变大.这些工作将为后续超快电子显微镜的发展及光发射电子源的设计奠定基础.

离子轰击二次发射电子枪束流引出问题的仿真与实验研究

为应对电子束荧光技术对电子枪的需求,本文开展了离子轰击二次发射电子枪的研究工作。首先介绍了离子轰击二次发射电子枪的工作原理,将工作过程划分为离子产生及引出、二次电子产生和引出两个部分并展开理论分析;基于辉光放电原理建立了简化的空气放电仿真模型,利用Comsol软件获得了正离子密度及其分布;对于加速室内的二次电子发射过程采用静电聚焦的方式聚焦电子束,利用Comsol软件基于Nelder-Mead算法获得二次电子引出的最佳结构参数;最后,搭建了电子枪原理样机,实验结果表明:采用空气作为工作气体,利用气体放电产生的正离子轰击金属铝使其发射二次电子,最终获得了加速电压为20 kV,束流强度为16 mA的电子束,完成了此类电子枪的原理验证并为性能提升工作奠定基础。

瓦里安Clinac 21EX直线加速器GFIL连锁的故障分析与维修

本文对本院瓦里安Clinac 21EX直线加速器9年内发生的GFIL连锁故障进行了总结。GFIL连锁故障的发生主要是由冷端Power Supply板、热端小电源板、热端Hot Deck Filament Power supply板、热端backplane板以及机架内Patch Panel板故障引起的。故障发生后,控制台会出现红色GFIL连锁警报,据详细的硬件状态分析故障原因并进行故障排除处理。本文阐述的5种故障类型基本囊括了与GFIL连锁相关的大部分硬件,根据硬件原理指出了快速有效的故障解决办法,为直线加速器维修提供参考。

瓦里安C系列加速器枪系统与联锁原理分析和典型案例

瓦里安C系列高能直线加速器均采用三极(栅极控制)电子枪系统,其故障率较高、解决难度较大,多表现为剂量率不稳定甚至不能出束,报GFIL枪灯丝联锁。本研究以iX平台的代表——Clinac iX为例,结合典型案例和技术图纸阐述枪控制系统的工作原理,通过分析电源电路和枪驱动等关键模块内部和模块之间的信号处理的流程和方向,发现问题症结并处理元器件解决问题,为工程师安全高效解决C系列乃至电路集成度和数字化程度非常高、以VitalBeam为代表的新一代高端技术平台的加速器的同类问题,提供解决思路和方法借鉴。

D波段行波管电子光学系统设计

提出一种用于D波段行波管的电子光学系统设计方案,包括电子枪和永磁聚焦系统,并进行了验证。电子枪采用经典皮尔斯电子枪结构,阴极发射面的外层设置阴极套壳,抑制阴极边缘杂散发射;采用圆柱形控制极替代锥形控制极,同时在聚焦极加负偏压,调节电子注的压缩状态。所设计电子枪工作电压为19 kV,提供电子注电流57 mA,注腰半径为0.068 mm,射程为14.9 mm。为在半径0.15 mm的电子通道中稳定地聚焦和传输电子注,永磁聚焦系统采用周期永磁聚焦系统。峰值磁场为布里渊磁场的2.9倍,增加了电子注刚性。模拟结果显示,传输的电子注最大波动半径小于0.1 mm。按所设计的电子光学系统加工组装了试验流通短管,测试结果显示电子注电流为49.83 mA,收集极电流为49.6 mA,对应电子注流通率达到99.5%,实现了设计目标。

电子束熔丝增材制造大功率电子枪研制

根据电子束熔丝增材制造需求,结合理论计算,利用三维造型软件设计了电子枪结构包括阴极组件、栅极、阳极、聚焦线圈、扫描线圈;利用模拟仿真软件对电子枪结构进行优化,最终得到优化后的电子枪栅极球面直径14 mm、阳极孔径3.5 mm、阳极倾角140°、阴阳极距离10 mm、聚焦线圈匝数1 800匝、磁轭间隙30 mm、线圈内径60 mm、外径150 mm;设计了电子枪聚焦及偏转扫描驱动电路,带载测试聚焦电流最大值可达1.49 A,偏转扫描最大电流可达±1.06 A,扫描频率达2 kHz;对电子枪性能进行测试,最高耐压达到-75 kV,功率达到30 kW,TC4的熔丝增材成形效率达到5.16 kg/h。研制的电子枪结构轻便、束流品质好、成形效率高,适合于用作真空室内动枪。

W波段平面集成行波管高频系统设计及验证

针对W波段平面一维阵列集成行波管设计,采用非半圆弯曲变形折叠波导慢波结构和聚焦极调制皮尔斯电子枪,基于CST、MTSS和Opera软件优化设计了集成行波管高频系统和电子光学系统,实现了W波段低电压小电流工作的低功率行波管设计,通过周期永磁(PPM)聚焦系统制管验证了高频系统和电子枪设计的合理性。测试结果表明,行波管在工作电压12.62 kV,工作电流31.6 mA条件下,输出功率大于10 W的带宽达到5 GHz,增益优于28 dB,总效率优于10%,测试结果与设计结果具有较好一致性,为W波段行波管实现阵列集成提供技术支撑。

基于磁透镜结构参数的电子枪磁聚焦特性分析

磁透镜是电子枪的重要组成部分,其结构会影响磁聚焦性能,从而影响束斑直径与电子束焊接质量。文章以国产ZD-VEBW系列高压电子束焊接设备电子枪为研究对象,构建电子枪束源与电磁聚焦结构的物理模型,并借助CST平台,仿真分析了球差影响下的束斑形貌和不同聚焦电流下磁透镜铁壳内径、铁壳开口对束斑直径的影响。设计环形挡板实现了磁透镜铁壳内径、铁壳开口参数的调整,并进行聚焦电流变化下的焊接实验研究。实验结果表明:磁透镜结构参数的合理设计可以达到更优的磁聚焦特性、更小束斑直径与更大的焊缝深宽比,实验验证了仿真结果的正确性,文章的研究对国产ZD-VEBW系列高压电子枪磁透镜结构的设计和该系列电子枪焊接质量的提升提供了理论和实验指导。