Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Self-Sustaining Relativistic Ionization Wave Launched by
  Sheath Field   We present experimental evidence supported by simulations of a relativistic
ionization wave launched into surrounding gas by the sheath field of a plasma
filament with high energy electrons. Such filament is created by irradiating a
clustering gas jet with a short pulse laser ($\sim$115 fs) at a peak intensity
of $5 \times 10^{17}$ W/cm$^2$. We observe an ionization wave propagating
radially through the gas for about 2 ps at 0.2-0.5 $c$ after the laser has
passed, doubling the initial radius of the filament. The gas is ionized by the
sheath field, while the longevity of the wave is explained by a moving field
structure that traps the high energy electrons near the boundary, maintaining a
strong sheath field despite the significant expansion of the plasma.

13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio