Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray Resonance in Crystal Cavities--Realization of Fabry-Perot
  Resonator for Hard X-rays   X-ray back diffraction from monolithic two silicon crystal plates of 25--150
um thick and a 40--150 um gap using synchrotron radiation of energy resolution
deltaE=0.36 meV at 14.4388 keV shows clearly resonance fringes inside the
energy gap and the total-reflection range for the (12 4 0) reflection. This
cavity resonance results from the coherent interaction between the X-ray
wavefields generated by the two plates with a gap smaller than the X-ray
coherence length. This finding opens up new opportunities for high-resolution
and phase-contrast X-ray studies, and may lead to new developments in X-ray
optics.

9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg