Manipulation of annular electron beams in plasmas

TL;DR

This paper investigates how self-generated and external magnetic fields influence the transport and shape of annular electron beams in plasma, enabling better control for various high-energy physics applications.

Contribution

It introduces a scheme to modify annular electron beams in plasma using magnetic fields, supported by theory and 3D simulations, to control beam width and stability.

Findings

Self-generated magnetic fields focus the beam and adjust its width.

External magnetic fields stabilize beams with orbital angular momentum.

Beam radius oscillates periodically under external magnetic influence.

Abstract

The annular electron beam has significant practical potential in high-energy physics and condensed matter physics, which can be used to edge-enhancement electron imaging, collimation of antiprotons in conventional linear accelerators, acceleration of positively particles like positrons, structured X-ray generation and manipulation of nanomaterials. The quality of an annular electron beam depends on its energy, flux and topology. In this article, we study the transport characteristics of annular electron beam in a plasma medium and propose a scheme to modify it. According to our theory and full three-dimensional LAPINS simulations, we have found that the self-generated magnetic field focuses the incident annular electron beam, enabling the adjustment of its annular width (AW). Besides, the annular electron beam, endowed with orbital angular momentum (OAM), exhibits contrasting transport characteristics compared to an electron beam devoid of OAM. The former requires an external magnetic field to ensure stable transportation in the plasma. Under the influence of this magnetic field, the radius of the annular electron beam oscillates periodically, with the direction of change whether increasing or decreasing dependent on the field's strength. In this case, the radius of annular electron beam will be affected by the external magnetic field and allows for the simultaneous adjustment of its radius and AW, significantly broadening its application range.