Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin