The self-focusing condition of a charged particle beam in a resistive plasma

Xiao-Chuan Ning,Zheng-Mao Sheng,Tian-Yi Liang,D Wu

doi:10.1017/s0022377821001021

Xiao-Chuan Ning, Zheng-Mao Sheng + Show 2 more

Open Access

https://doi.org/10.1017/s0022377821001021

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Abstract

The self-focusing condition of a charged particle beam in a resistive plasma has been studied. When plasma heating is weak, the beam focusing is intensified by increasing the beam density or velocity. However, when plasma heating is strong, the beam focusing is only determined by the beam velocity. Especially, in weak heating conditions, the beam trends to be focused into the centre as a whole, and in strong heating conditions, a double-peak structure with a hollow centre is predicted to appear. Furthermore, it is found that the beam radius has a significant effect on focusing distance: a larger the beam radius will result in a longer focusing distance. Simulation results also show that when the beam radius is large enough, filamentation of the beam appears. Our results will serve as a reference for relevant beam–plasma experiments and theoretical analyses, such as heavy ion fusion and ion-beam-driven high energy density physics.

Highlights

Transport of a charged particle beam in a background plasma is the foundation for a variety of applications, such as inertial confinement fusion (Roth et al 2001; Logan, Perkins & Barnard 2008; Frolova, Khishchenko & Charakhch’yan 2019), high-energy particle accelerators and colliders (Govil et al 1999), radiography (Sheng et al 2014), astrophysics (Bennett 1934; Alfvén 1939; Spitkovsky 2007) and material etching (Lami et al 2020)
The first is that when a charged particle beam is injected into a resistive plasma, we assume the beam is quickly neutralized by plasma electrons
In the weak heating regime, the beam is focused to the centre as a whole, while in the strong heating regime, though the beam hollowing occurs near the centre, the beam can be focused away from the centre

Summary

Introduction

Transport of a charged particle beam in a background plasma is the foundation for a variety of applications, such as inertial confinement fusion (Roth et al 2001; Logan, Perkins & Barnard 2008; Frolova, Khishchenko & Charakhch’yan 2019), high-energy particle accelerators and colliders (Govil et al 1999), radiography (Sheng et al 2014), astrophysics (Bennett 1934; Alfvén 1939; Spitkovsky 2007) and material etching (Lami et al 2020). Beam focusing may occur in all kinds of phenomena associated with beam–plasma physics as mentioned above A century ago, Bennett published two papers on the magnetically self-focusing relation of mixed streams consisting of electrons and ions (Bennett 1934, 1955), which, to the best of our knowledge, are the pioneering work in this field. Even after such a long time, focusing was remained a hot topic, especially in the last twenty years.

Theory

Simulation

Conclusions