Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Brightness of synchrotron radiation from wigglers   According to literature, while calculating the brightness of synchrotron
radiation from wigglers, one needs to account for the so called
`depth-of-field' effects. In fact, the particle beam cross section varies along
the wiggler. It is usually stated that the effective photon source size
increases accordingly, while the brightness is reduced. Here we claim that this
is a misconception originating from an analysis of the wiggler source based on
geometrical arguments, regarded as almost self-evident. According to
electrodynamics, depth-of-field effects do not exist: we demonstrate this
statement both theoretically and numerically, using a well-known
first-principle computer code. This fact shows that under the usually accepted
approximations, the description of the wiggler brightness turns out to be
inconsistent even qualitatively. Therefore, there is a need for a well-defined
procedure for computing the brightness from a wiggler source. We accomplish
this task based on the use of a Wigner function formalism. In the geometrical
optics limit computations can be performed analytically. Within this limit, we
restrict ourselves to the case of the beam size-dominated regime, which is
typical for synchrotron radiation facilities in the X-ray wavelength range. We
give a direct demonstration of the fact that the apparent horizontal source
size is broadened in proportion to the beamline opening angle and to the length
of the wiggler. While this effect is well-understood, a direct proof appears
not to have been given elsewhere. We consider the problem of the calculation of
the wiggler source size by means of numerical simulations alone, which play the
same role of an experiment. We report a significant numerical disagreement
between exact calculations and approximations currently used in literature.

20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math