Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electric field dynamics and ion acceleration in the self-channeling of a
  superintense laser pulse   The dynamics of electric field generation and radial acceleration of ions by
a laser pulse of relativistic intensity propagating in an underdense plasma has
been investigated using an one-dimensional electrostatic, ponderomotive model
developed to interpret experimental measurements of electric fields [S. Kar et
al, New J. Phys. *9*, 402 (2007)]. Ions are spatially focused at the edge of
the charge-displacement channel, leading to hydrodynamical breaking, which in
turns causes the heating of electrons and an "echo" effect in the electric
field. The onset of complete electron depletion in the central region of the
channel leads to a smooth transition to a "Coulomb explosion" regime and a
saturation of ion acceleration.

21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ