Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gamma-ray generation in ultrahigh-intensity laser-foil interactions   Incoherent photon emission by ultrarelativistic electrons in the normal
incidence of a laser pulse on a foil is investigated by means of
three-dimensional numerical simulations in the range of intensities $2 \times
10^{21} \text{--} 2 \times 10^{25} \text{W} \, \text{cm}^{-2}$ and electron
densities $2 \times 10^{22} \text{--} 1 \times 10^{24} \text{cm}^{-3}$. We
focus on properties of the resulting synchrotron radiation, such as its overall
energy, directivity of the radiation pattern and slope of the energy spectrum.
Regimes of laser-foil interactions are studied in the framework of a simple
analytical model. The laser-plasma parameters for efficient gamma-ray
generation are found and revealed to be close to the parameters for
relativistic foil motion. It is shown that in the case of oblique incidence of
a $3 \text{PW}$, $10 \text{fs}$ laser pulse on a thin foil about $10^{8}
\text{photons}/0.1\% \text{bandwidth}$ are produced at the energy level of $1
\text{MeV}$ that significantly exceeds performance of the modern Compton
gamma-ray sources. Various applications of the gamma-ray bunches are discussed.

37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin