We report on the experimental observation of the focusing effect of a 50MeV accelerator electron beam in a gas-discharge plasma target. The plasma is generated by igniting an electric discharge in two collinear quartz tubes, with the currents up to 1.5kA flowing in opposite directions in either of the two tubes. In such plasma current configuration, the electron beam is defocused in the first discharge tube and focused with a stronger force in the second one. With symmetric plasma currents, asymmetric effects are, however, induced on the beam transport process and the beam radius is reduced by a factor of 2.6 compared to the case of plasma discharge off. Experimental results are supported by two-dimensional particle-in-cell simulations.

High Energy Electron Radiography (HEER) has been proposed as a new material diagnostic technology in recent years. The main features of this technology are the strong penetrating power, high space-time resolution, and large area density diagnostic range. Therefore, it is considered as one of the effective diagnostic methods in the field of high energy density material diagnosis. For further research of HEER, the High Energy Electron Radiography Platform in Lanzhou (HERPL) has designed and built as a dedicated experimental platform of HEER, which is mainly composed of a 50MeV electron linear accelerator based on a thermionic cathode RF gun, and a set of quadrupole magnet image systems. In this paper, the HEER experiment has completed and the spatial resolution of 1μm, the density resolution of 1% was obtained which reached the world record of HEER.

A CW mode RF modulated grid-controlled thermionic electron gun was proposed by Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS) for some high average current electron accelerators requirements. The RF modulated grid-controlled thermionic electron gun was selected for these purposes due to its simplicity and cost savings. The experimental proof test of this type electron gun was conducted. The RF power supply at 107.5 MHz for the grid modulation can be adjusted from 10 W to 70 W. The RF power is coupled into the gun of grid-cathode through a RF&DC modulator. The electromagnetic field and RF simulation of the modulator is presented here. The gun structure and the beam dynamics design are also shown in the paper. The cathode assembly and the electron guns are tested on a 10 kV test bench for beam characterization. The CW mode 107.5 MHz electron beam obtained from the proof test, which is important for future high average current electron injectors development.

As a new scheme, High Energy Electron Radiography (HEER) was considered as an effective diagnostic tool in the mesoscale sciences due to its high spatial temporal resolution and large area density diagnostic range. Some improvements were implemented to achieve high spatial resolution using a 50 MeV electron beam in Lanzhou, China. These included improving the uniformity of the beam transverse distribution, optimizing the energy spread and increasing the magnet lens magnification. Then the HEER image was collected by a CCD camera with image processing program and in-situ spatial resolution optimization adjustment program. To the best of our knowledge, the achieved spatial resolution of 0.8 mu m constitutes a world record. The details of this experiment are described in this publication.

兰州高能电子成像实验研究平台是中国科学院近代物理研究所建造的唯一专用于高能电子成像及相关领域的实验研究平台,目前已完成第一阶段基于热阴极微波电子枪电子直线加速器的研制,电子束能量50 MeV,最大宏脉冲束流300 mA,达到了设计指标并通过技术测试.开展了高能电子成像实验,空间分辨4 μm,获得了预期结果.

针对近代物理研究所高能电子成像实验和电子直线加速器稳定运行的要求,基于实验物理与工业控制系统(EPICS)设计了一套直线加速器控制系统.首先介绍了控制系统的总体设计,然后较为全面地介绍了各子系统的硬件结构和软件开发,最后介绍了系统远程界面和测试结果.控制系统已经投入运行一年,运行过程中性能可靠稳定,满足电子直线加速器的控制要求.

针对兰州高能电子成像实验平台加速器,设计了基于多次改变聚焦强度法的实验来测量束流发射度.采用YAG屏及CCD相机来采集束斑图像,编制了一套完整的计算软件,具有测量方便,计算快速可靠等特点,该测量为后续的高能电子成像实验提供了相关信息.测试结果表明,x方向发射度与理论计算设计接近,y方向发射度与理论计算偏差较大,有待进一步对加速器进行优化调试.

为了能开展高能电子成像相关实验研究,中国科学院近代物理研究所建造了一台S波段的射频电子直线加速器.为保证实验用束流品质和加速器稳定运行的要求,设计了一套低电平控制系统,利用上下变频、IQ解调技术,实现了相位的反馈控制.本文介绍了低电平控制系统的设计及数字化算法的实现,给出了系统闭环实验的测试结果,实现相位控制精度达到±0.5°(峰峰值)和0.1108°(均方根).该系统利用成熟的商业化模拟微波器件和相关的PXI板卡实现,基于LabVIEW软件开发了相关的控制程序和界面,具有搭建方便、开发时间短、结构简单紧凑、易于使用和维护的特点.

In this paper, we propose a new method for static mesoscale sample diagnosis using three-dimensional radiography with high-energy electron radiography (HEER). The principle of three-dimensional high-energy electron radiography (TDHEER) is elucidated, and the feasibility of this method is confirmed by start-to-end simulation results. TDHEER is realized by combining HEER with the three-dimensional reconstruction method, by which more information about the samples can be attained, especially regarding the samples’ internal structures. With our study, the internal structures and the three-dimensional positions of the spherical sample are determined with a ~3 μm resolution. We believe that this new method enhances the HEER diagnostic capability and extends its application potential in mesoscale sciences.

Using a high energy electron beam for the imaging of high density matter with both high spatial-temporal and areal density resolution under extreme states of temperature and pressure is one of the critical challenges in high energy density physics . When a charged particle beam passes through an opaque target, the beam will be scattered with a distribution that depends on the thickness of the material. By collecting the scattered beam either near or off axis, so-called bright field or dark field images can be obtained. Here we report on an electron radiography experiment using 45 MeV electrons from an S-band photo-injector, where scattered electrons, after interacting with a sample, are collected and imaged by a quadrupole imaging system. We achieved a few micrometers (about 4 micrometers) spatial resolution and about 10 micrometers thickness resolution for a silicon target of 300-600 micron thickness. With addition of dark field images that are captured by selecting electrons with large scattering angle, we show that more useful information in determining external details such as outlines, boundaries and defects can be obtained.