Design of a compact electron radiography system with electron source from laser wakefield accelerator

Xueqing Yan,Yixing Geng,Jungao Zhu,Haiyang Lu,Chaofan Xiao,Senlin Huang,Hongbin Zhuo,Sheng Zhao,Cangtao Zhou,Zhiyi Xu,Meifu Lai,Hua Zhang,Jiaxin Liu,Chengzhi Xie,Yanying Zhao

doi:10.1063/5.0042401

Abstract

A compact electron radiography system has been designed with high gradient permanent magnet quadrupoles with 2.5 times magnification. Quasi-monoenergetic electron bunches with energies ranging from 100 to 200 MeV are generated from a laser wakefield accelerator (LWFA) acting as the electron source for the system. A matching segment composed of three quadrupoles before the objective plane creates a correlation between the position and the angle for the electrons, illuminating the observed object improved the resolution of the system. We expect electron radiography with 100-MeV ultrafast electron bunches to be widely adopted for many applications, especially considering the micron-level spatial resolution and sub-picosecond temporal resolution of the electron source from the LWFA. Since the laser system needed for generating 100–200 MeV electrons using the LWFA is roughly around 40 TW, the whole system can be effectively table-top in size, which is favorable for movable applications.

Highlights

Transmission electron microscopy (TEM) employs relatively low-energy electrons as a primary detection method
Much effort has been focused on the design of electron radiography systems with electron energies ranging from MeV to GeV, improving the spatial resolution to the submicrometer level and the temporal resolution to the picosecond level
8.8-μm resolution imaging has been achieved at the Stanford Linear Accelerator Center (SLAC) through transmission high-energy electron microscopy (THEEM) using a 14-GeV electron beam to image the melting and freezing process of an alloy (Bi80Sn20), which demonstrates the advantage of high energy electrons

Summary

INTRODUCTION

Transmission electron microscopy (TEM) employs relatively low-energy electrons as a primary detection method. Scitation.org/journal/adv electron beams can be achieved in laser wakefield acceleration, with charges of tens to hundreds of picocoulombs, pulse duration as short as tens of femtoseconds, and good beam quality, low energy spread, small divergence, and high stability.. We have designed an electron radiography system with HGPMQs, with 2.5 times magnification for electron bunches with a central energy of 100 MeV. We have optimized the electron parameters, such as energy dispersion and stability, to reduce the aberration for radiography due to the electron bunch characteristics generated through laser wakefield acceleration. The resolution is around the 100-μm-level, as recorded in previous direct imaging experiments using image plates.34 With such an electron source from a laser plasma accelerator, this imaging system could provide a field of view around 1.5 mm (1/e2). Q1 (d: 15 mm) Q2 (d: 30 mm) Q3 (d: 15 mm) Q4 (d: 15 mm) Q5 (d: 15 mm) Q6 (d: 15 mm) Q7 (d: 15 mm) Aperture (after Q6) Magnification

D2 D3 D4 D5 D6 D7 D8 D9 Matching segment length Radiography system length

Findings

CONCLUSION