arXiv subjects

L. B. Ju

Publications and source records attributed to L. B. Ju.

3 recordsLinked to original sources

arXiv2019

Simulating the external magnetic field in short-pulse intense laser-plasma interaction

Imposing an external magnetic field in short-pulse intense laser-plasma interaction is of broad scientific interest in related plasma research areas. We propose a simple method using a virtual current layer by introducing an extra current density term to simulate the external magnetic field, and demonstrate it with three-dimensional particle-in-cell simulations. The field distribution and its evolution in sub-picosecond time scale are obtained. The magnetization process takes a much longer time than that of laser-plasma interaction due to plasma diamagnetism arising from collective response. The long-time evolution of magnetic diffusion and diamagnetic current can be predicted based on a simplified analytic model in combination with simulations.

physics.plasm-ph↗

arXiv2018

Direction and divergence control of laser-driven energetic proton beam using a disk-solenoid target

A scheme for controlling the direction of energetic proton beam driven by intense laser pulse is proposed. Simulations show that a precisely directed and collimated proton bunch can be produced by a sub-picosecond laser pulse interacting with a target consisting of a thin solid-density disk foil with a solenoid coil attached to its back at the desired angle. It is found that two partially overlapping sheath fields are induced. As a result, the accelerated protons are directed parallel to the axis of the solenoid, and their spread angle is also reduced by the overlapping sheath fields. The proton properties can thus be controlled by manipulating the solenoid parameters. Such highly directional and collimated energetic protons are useful in the high-energy-density as well as medical sciences.

physics.plasm-ph↗

arXiv2017

Injection dynamics of direct-laser accelerated electrons in a relativistic transparency regime

The dynamics of electron injection in the direct laser acceleration (DLA) regime was investigated by means of three-dimensional particle-in-cell simulations and theoretical analysis. It is shown that when an ultra-intense laser pulse propagates into a near-critical density or relativistically transparent plasma, the longitudinal charge-separation electric field excites an ion wave. The ion wave modulates the local electric field and acts as a set of potential wells to guide the electrons, located on the edge of the plasma channel, to the central region, where the DLA takes place later on. In addition, it is pointed out that the self-generated azimuthal magnetic fields tend to suppress the injection process of electrons by deflecting them away from the laser field region. Understanding these physical processes paves the way for further optimizing the properties of direct-laser accelerated electron beams and the associated X/gamma-ray sources.

physics.plasm-ph↗