Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on photon pulse duration from longitudinal electron beam
  diagnostics at a soft X-ray free-electron laser   The successful operation of X-ray free-electron lasers (FELs), like the Linac
Coherent Light Source or the Free-Electron Laser in Hamburg (FLASH), makes
unprecedented research on matter at atomic length and ultrafast time scales
possible. However, in order to take advantage of these unique light sources and
to meet the strict requirements of many experiments in photon science, FEL
photon pulse durations need to be known and tunable. This can be achieved by
controlling the FEL driving electron beams, and high-resolution longitudinal
electron beam diagnostics can be utilized to provide constraints on the
expected FEL photon pulse durations. In this paper, we present comparative
measurements of soft X-ray pulse durations and electron bunch lengths at FLASH.
The soft X-ray pulse durations were measured by FEL radiation pulse energy
statistics and compared to electron bunch lengths determined by
frequency-domain spectroscopy of coherent transition radiation in the terahertz
range and time-domain longitudinal phase space measurements. The experimental
results, theoretical considerations, and simulations show that high-resolution
longitudinal electron beam diagnostics provide reasonable constraints on the
expected FEL photon pulse durations. In addition, we demonstrated the
generation of soft X-ray pulses with durations below 50 fs (FWHM) after the
implementation of the new uniform electron bunch compression scheme used at
FLASH.

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The categories of this paper are: astro-ph
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The categories of this paper are: eess
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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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: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: math