Charged particle reflection by a planar artificially structured boundary with electrostatic plugging

2020

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A purely magnetic applied field may provide plasma confinement under conditions where the bulk of the plasma is effectively free of the applied magnetic field. The applied magnetic field surrounds the bulk of the plasma, and plasma particles that are incident on the applied magnetic field can be reflected back into the effectively unmagnetized region of plasma. The concept belongs to a class of magnetic plasma confinement approaches studied long ago, for which some experimental results indicated that classical (collision-based) cross-magnetic-field transport may occur. However, multiple magnetic coils are required to be immersed within the confined plasma, and rapid plasma loss may occur if material structures are present, which pass through the plasma (e.g., to hold the immersed coils in place). In the work reported, the concept is studied in combination with magnetic plasma expulsion [R. E. Phillips and C. A. Ordonez, Phys. Plasmas 25, 012508 ( 2018)], which would be employed to keep plasma away from material structures that pass through the plasma. A planar model is used for the study. A classical trajectory Monte Carlo simulation is carried out on particles that are independently incident on the applied magnetic field. With monoenergetic incident particles, the results indicate that the applied magnetic field can reflect all independently incident particles in certain regions of parameter space. Prospects for achieving three-dimensional magnetic confinement of an effectively unmagnetized plasma with a Maxwellian velocity distribution are discussed.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic confinement of effectively unmagnetized plasma particles

2020

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“…The possibility of using a sequence of magnetic cusps with the addition of electrostatic plugging is described in Ref. 10, where a classical trajectory Monte Carlo study of single particle trajectories was reported. The present work contributes to an improved theoretical understanding of how a non-neutral electron plasma responds self-consistently to a spatially changing magnetic field, such as within a magnetic cusp or Penning trap with an axially varying magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Electrostatic equilibria of non-neutral plasmas confined in a Penning trap with axially varying magnetic field

Lane

2019

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A procedure for computing the electrostatic equilibria of non-neutral plasmas in a Penning trap with a nonuniform magnetic field by solving Poisson's equation using an iterative method is described. Plasma equilibria in a model Penning trap with high and low field regions are computed. The plasma is assumed to follow the Boltzmann density distribution along magnetic field lines. Correspondence with previous investigations examining similar configurations analytically and using particle-in-cell simulations is found. The relationship between the plasma density in low and high field regions is examined for various plasma temperatures, densities, magnetic mirror ratios, and plasma and electrode radii. An analytical description of the radial density profile in the high field region is developed and compared with the computed equilibria. A concept is described for cooling a positron plasma with laser-cooled ions trapped axially within a high magnetic field region, while antiprotons are trapped axially separated from the laser-cooled ions within a low field region, and the positron plasma extends to both regions.

Artificially structured boundary plasma trap

Hedlof

2019

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A computer simulation is presented of single-species non-neutral plasma confinement using an artificially structured boundary. The artificially structured boundary produces a spatially periodic static electromagnetic field along the plasma periphery such that the spatial period of the applied field is much smaller than the dimensions of the confined plasma. The simulated non-neutral plasma self-consistently produces an electrostatic potential energy well for oppositely signed charged particles. The results support the prospect of developing plasma spacecharge based confinement, with an unmagnetized plasma of one species of charged particles confined by an electric field produced by an edge-confined plasma of a second species of charged particles. The Warp particle-in-cell code is used for the simulations.