Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase Fresnel Lens Development for X-ray and Gamma-ray Astronomy   In principle, diffractive optics, particularly Phase Fresnel Lenses (PFLs),
offer the ability to construct large, diffraction-limited, and highly efficient
X-ray/$\gamma$-ray telescopes, leading to dramatic improvement in angular
resolution and photon flux sensitivity. As the diffraction limit improves with
increasing photon energy, gamma-ray astronomy would offer the best angular
resolution over the entire electromagnetic spectrum. A major improvement in
source sensitivity would be achieved if meter-size PFLs can be constructed, as
the entire area of these optics focuses photons. We have fabricated small,
prototype PFLs using Micro-Electro-Mechanical Systems (MEMS) fabrication
techniques at the University of Maryland and measured near diffraction-limited
performance with high efficiency using 8 keV and higher energy X-rays at the
GSFC 600-meter Interferometry Testbed. A first generation, 8 keV PFL has
demonstrated imaging corresponding to an angular resolution of approximately 20
milli-arcseconds with an efficiency $\sim$70$\%$ of the theoretical
expectation. The results demonstrate the superior imaging potential in the
X-ray/$\gamma$-ray energy band for PFL-based optics in a format that is
scalable for astronomical instrumentation. Based upon this PFL development, we
have also fabricated a `proof-of-principle' refractive-diffractive achromat and
initial measurements have demonstrated nearly uniform imaging performance over
a large energy range. These results indicate that the chromaticity inherent in
diffractive optics can be alleviated.

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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: cond-mat
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat