Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fast electron propagation in Ti foils irradiated with sub-picosecond
  laser pulses at $I\lambda^{2} > 10^{18}$ Wcm$^{-2} \mu m^{2}$   We have studied the propagation of fast electrons through laser irradiated Ti
foils by monitoring the emission of hard X-rays and K-{\alpha} radiation from
bare foils and foils backed by a thick epoxy layer. Key observations include
strong refluxing of electrons and divergence of the electron beam in the foil
with evidence of magnetic field collimation. Our diagnostics have allowed us to
estimate the fast electron temperature and fraction of laser energy converted
to fast electrons. We have observed clear differences between the fast electron
temperatures observed with bare and epoxy backed targets which may be due to
the effects of refluxing.

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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat