Significance of self magnetic field in long-distance collimation of laser-generated electron beams

TL;DR

This paper investigates how self magnetic fields contribute to the long-distance collimation of laser-generated electron beams, revealing their critical role in maintaining beam focus over extended distances.

Contribution

It demonstrates through simulations and experiments that self magnetic fields are essential for electron beam collimation, clarifying the metallic wire's role in balancing space-charge effects.

Findings

Self magnetic fields provide a restoring force for collimation.

Simulated patterns agree with experimental observations.

Wire length affects beam divergence and collimation stability.

Abstract

Long-distance collimation of fast electron beams generated by laser-metallic-wire targets has been observed in recent experiments, while the mechanism behind this phenomenon remains unclear. In this work, we investigate in detail the laser-wire interaction processes with a simplified model and Classical Trajectory Monte Carlo simulations, and demonstrate the significance of the self magnetic fields of the beams in the long-distance collimation. Good agreements of simulated image plate patterns with various experiments and detailed analysis of electron trajectories show that the self magnetic fields provide restoring force that is critical for the beam collimation. By studying the wire-length dependence of beam divergence in certain experiments, we clarify that the role of the metallic wire is to balance the space-charge effect and thus maintain the collimation.