Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gain-guided X-ray free-electron laser oscillator   The X-ray free-electron laser oscillator (XFELO) has recently been
reconsidered a promising candidate for producing high-brightness, fully
coherent pulses in the hard X-ray regime. This letter proposes a gain-guided
XFELO scheme, avoiding the external focusing elements required for conventional
configuration. Self-consistent theoretical analysis and three-dimensional
numerical simulation results verify that the X-ray transverse mode in such an
"unstable" cavity is stable and robust due to electron beam gain-guiding. This
scheme is capable of generating 14.3 keV photons of FEL radiation with peak
power on the order of a gigawatt using Shanghai coherent light source
parameters. The output pulse energy and transverse and longitudinal coherence
are comparable with those from conventional XFELOs. This promising scheme is
expected to contribute significantly to the construction and operation of a
real XFELO.

22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th