Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear equilibria and emittance growth in plasma wakefield
  accelerators with ion motion   The plasma wakefield accelerator may accelerate particles to high energy in a
future linear collider with unprecedented acceleration gradients, exceeding the
GeV/m range. Beams for this application would have extremely high brightness
and, subject to the intense plasma ion-derived focusing, they would achieve
densities high enough to induce the plasma ions to collapse into the beam
volume. This non-uniform ion density gives rise to strong nonlinear focusing
which may lead to deleterious beam emittance growth. The effects of ion
collapse and their mitigation has been investigated recently through
particle-in-cell simulations, which show that by dynamically matching the beam
to the focusing of the collapsed ion distribution, one may avoid serious
emittance growth. We extend this work by exploring the near-equilibrium state
of the beam-ion system reached after the ions have collapsed, a condition
yielding the emittance growth mitigation observed. We show through PIC
simulations and analytical theory that in this case a dual electron beam-ion
Bennett-type equilibrium distribution is approached. Here, the beam and ion
distributions share nearly the same shape, which generates nonlinear transverse
electromagnetic fields. We exploit a Bennett-type model to study beam phase
space dynamics and emittance growth over time scales much longer than permitted
by PIC simulations through use of a 2D symplectic tracking code with Monte
Carlo scattering based on Moliere's theory of small angle multiple scattering.
We find that while phase space diffusion due to parametric excitations of the
beam size due to plasma non-uniformity is negligible, scattering from collapsed
ions gives rise to manageable emittance growth in the case of a linear
collider. The implications of these results on experiments planned at FACET-II
are examined.

29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph