Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simulation studies of the behavior of positrons in a microtrap with long
  aspect ratio   The charged particles storage capacity of microtraps (micro-Penning-Malmberg
traps) with large length to radius aspect ratios and radii of the order of tens
of microns was explored. Simulation studies of the motions of charged particles
were conducted with particle-in-cell WARP code and the Charged Particle Optics
(CPO) program. The new design of the trap consisted of an array of microtraps
with substantially lower end electrodes potential than conventional
Penning-Malmberg traps, which makes this trap quite portable. It was
computationally shown that each microtrap with 50 micron radius stored
positrons with a density (1.6x10^11 cm^-3) even higher than that in
conventional Penning-Malmberg traps (about 10^11 cm^-3) while the confinement
voltage was only 10 V. It was presented in this work how to evaluate and lower
the numerical noise by controlling the modeling parameters so the simulated
plasma can evolve toward computational equilibrium. The local equilibrium
distribution, where longitudinal force balance is satisfied along each magnetic
field line, was attained in time scales of the simulation for plasmas
initialized with a uniform density and Boltzmann energy distribution. The
charge clouds developed the expected radial soft edge density distribution and
rigid rotation evolved to some extent. To reach global equilibrium (i.e. rigid
rotation) longer runs are required. The plasma confinement time and its
thermalization were independent of the length. The length-dependency, reported
in experiments, is due to fabrication and field errors. Computationally, more
than one hundred million positrons were trapped in one microtrap with 50 micron
radius and 10 cm length immersed in a 7 T uniform, axial magnetic field, and
the density scaled as r^-2 down to 3 micron. Larger densities were trapped with
higher barrier potentials.

22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: supr-con