Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 5.5-7.5 MeV Proton generation by a moderate intensity ultra-short laser
  interaction with H2O nano-wire targets   We report on the first generation of 5.5-7.5 MeV protons by a moderate
intensity short-pulse laser (4.5 \times 1017 W/cm^2, 50 fsec) interacting with
H2O nano-wires (snow) deposited on a Sapphire substrate. In this setup, the
laser intensity is locally enhanced by the tip of the snow nano-wire, leading
to high spatial gradients. Accordingly, the plasma near the tip is subject to
enhanced ponderomotive potential, and confined charge separation is obtained.
Electrostatic fields of extremely high intensities are produced over the short
scale length, and protons are accelerated to MeV-level energies.

17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas