Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-short, MeV-scale laser-plasma positron source for positron
  annihilation lifetime spectroscopy   Sub-micron defects represent a well-known fundamental problem in
manufacturing since they can significantly affect performance and lifetime of
virtually any high-value component. Positron annihilation lifetime spectroscopy
is arguably the only established method capable of detecting defects down to
the sub-nanometer scale but, to date, it only works for surface studies, and
with limited resolution. Here, we experimentally and numerically show that
laser-driven systems can overcome these well-known limitations, by generating
ultra-short positron beams with a kinetic energy tuneable from 500 keV up to 2
MeV and a number of positrons per shot in a 50 keV energy slice \color{black}
of the order of $10^3$. Numerical simulations of the expected performance of a
typical mJ-scale kHz laser demonstrate the possibility of generating MeV-scale
narrow-band and ultra-short positron beams with a flux exceeding $10^5$
positrons/s, of interest for fast volumetric scanning of materials at high
resolution.

15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess