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Title: Plasma asymmetry due to the magnetic filter in fusion-type negative ion sources: Comparisons between two and three-dimensional particle-in-cell simulations

Abstract

Previously reported 2D Particle-In-Cell Monte Carlo Collisions (PIC-MCC) simulations of negative ion sources under conditions similar to those of the ITER neutral beam injection system have shown that the presence of the magnetic filter tends to generate asymmetry in the plasma properties in the extraction region. In this paper, we show that these conclusions are confirmed by 3D PIC-MCC simulations and we provide quantitative comparisons between the 2D and 3D model predictions.

Authors:
;  [1];  [2]
  1. Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France)
  2. (France)
Publication Date:
OSTI Identifier:
22299859
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANIONS; ASYMMETRY; BEAM INJECTION; COLLISIONS; COMPARATIVE EVALUATIONS; ITER TOKAMAK; MAGNETIC FILTERS; MONTE CARLO METHOD; PLASMA; SIMULATION; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Fubiani, G., E-mail: gwenael.fubiani@laplace.univ-tlse.fr, Boeuf, J. P., and CNRS, LAPLACE, F-31062 Toulouse. Plasma asymmetry due to the magnetic filter in fusion-type negative ion sources: Comparisons between two and three-dimensional particle-in-cell simulations. United States: N. p., 2014. Web. doi:10.1063/1.4891658.
Fubiani, G., E-mail: gwenael.fubiani@laplace.univ-tlse.fr, Boeuf, J. P., & CNRS, LAPLACE, F-31062 Toulouse. Plasma asymmetry due to the magnetic filter in fusion-type negative ion sources: Comparisons between two and three-dimensional particle-in-cell simulations. United States. doi:10.1063/1.4891658.
Fubiani, G., E-mail: gwenael.fubiani@laplace.univ-tlse.fr, Boeuf, J. P., and CNRS, LAPLACE, F-31062 Toulouse. Tue . "Plasma asymmetry due to the magnetic filter in fusion-type negative ion sources: Comparisons between two and three-dimensional particle-in-cell simulations". United States. doi:10.1063/1.4891658.
@article{osti_22299859,
title = {Plasma asymmetry due to the magnetic filter in fusion-type negative ion sources: Comparisons between two and three-dimensional particle-in-cell simulations},
author = {Fubiani, G., E-mail: gwenael.fubiani@laplace.univ-tlse.fr and Boeuf, J. P. and CNRS, LAPLACE, F-31062 Toulouse},
abstractNote = {Previously reported 2D Particle-In-Cell Monte Carlo Collisions (PIC-MCC) simulations of negative ion sources under conditions similar to those of the ITER neutral beam injection system have shown that the presence of the magnetic filter tends to generate asymmetry in the plasma properties in the extraction region. In this paper, we show that these conclusions are confirmed by 3D PIC-MCC simulations and we provide quantitative comparisons between the 2D and 3D model predictions.},
doi = {10.1063/1.4891658},
journal = {Physics of Plasmas},
number = 7,
volume = 21,
place = {United States},
year = {Tue Jul 15 00:00:00 EDT 2014},
month = {Tue Jul 15 00:00:00 EDT 2014}
}
  • Results from a 3D self-consistent Particle-In-Cell Monte Carlo Collisions (PIC MCC) model of a high power fusion-type negative ion source are presented for the first time. The model is used to calculate the plasma characteristics of the ITER prototype BATMAN ion source developed in Garching. Special emphasis is put on the production of negative ions on the plasma grid surface. The question of the relative roles of the impact of neutral hydrogen atoms and positive ions on the cesiated grid surface has attracted much attention recently and the 3D PIC MCC model is used to address this question. The resultsmore » show that the production of negative ions by positive ion impact on the plasma grid is small with respect to the production by atomic hydrogen or deuterium bombardment (less than 10%)« less
  • Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo ismore » significantly reduced to 6%. This value reasonably agrees with the experimental result.« less
  • We have used the three-dimensional, particle-in-cell code QUICKSILVER [J. P. Quintenz, {ital et} {ital al}., Lasers and Particle Beams {bold 12}, 283 (1994)] to simulate radial applied-{ital B} ion diodes on the particle beam fusion accelerator II at Sandia National Laboratories. The simulations agree well with experiments early in the beam pulse, but differ substantially as the ion-beam current increases. This is attributed to the oversimplified ion emission model. We see the same instabilities seen in earlier simulations with idealized diode geometries; Early in time there is a diocotron instability, followed by a transition to an {open_quote}{open_quote}ion mode{close_quote}{close_quote} instability atmore » much lower frequency. The instability-induced beam divergence for the {approximately}10 MeV beam during the diocotron phase is {lt}10 mrad, significantly less than the total beam divergence in experiments early in the pulse, but increases to {approx_gt}25 mrad after the transition. The ion mode has a distinct harmonic structure along the applied field lines, making the instability transition sensitive to the diode geometry. The ion mode instability in our latest simulations is consistent with evidence of instabilities from recent experiments. {copyright} {ital 1996 American Institute of Physics.}« less
  • To fulfill the need of a plasma ion source for SPIRAL-2 and EURISOL, capable of producing radioactive ion beams under strong radiation, the first prototype of the IRENA (Ionization by Radial Electrons Neat Adaptation) ion source has been designed. For designing an optimized prototype based on the first one, the influence of the geometrical parameters on the electron trajectories is investigated by means of two-dimensional/three-dimensional (3D) simulations. Due to the strong space charge effect in this kind of ion source, 3D simulations help particularly to better estimate effects on ion confinement and extraction. Simulation constructions will be presented and resultsmore » discussed.« less
  • The performance of large negative ion sources used in neutral beam injection systems is in long pulses mainly determined by the increase of the currents of co-extracted electrons. This is in particular a problem in deuterium and limits the ion currents which are for long pulses below the requirements for the ITER source. In the source of the ELISE test facility, the magnetic field in front of the first grid, which is essential to reduce the electron current, is generated by a current of several kA flowing through the plasma facing grid. Weakening of this field by the addition ofmore » permanent magnets placed close to the lateral walls has led to a reduction of the electron current by a factor three without loss of ion current when source was operated in volume production. If this effect can be validated for the cesiated source, it would be a large step towards achieving the ITER parameter in long pulses.« less