Modeling of a negative ion source. II. Plasma-gas coupling in the extraction region

Taccogna, F.; Schneider, Robert; Longo, S.; Capitelli, M.

doi:10.1063/1.2985854

Cited by 33 publications

(21 citation statements)

References 46 publications

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“…Different bulk collisions are implemented using Test Particle and Direct Simulation Monte Carlo Collision techniques [30]. The list of relevant collisions included are reported in [31].…”

Section: Description and Assumptions Of Numerical Modelmentioning

confidence: 99%

PIC modeling of negative ion sources for fusion

Taccogna

Minelli

2017

New J. Phys.

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This work represents the first attempt to model the full-size ITER negative ion source prototype including expansion, extraction and part of the acceleration regions keeping the resolution fine enough to resolve every single aperture of the extraction grid. The model consists of a 2.5-dimensional Particle-in-Cell/Monte Carlo Collision representation of the plane perpendicular to the filter field lines. Both the magnetic filter and electron deflection fields have been included. A negative ion current density of = --j 500 A m H 2 produced by neutral conversion from the plasma grid is used as fixed parameter, while negative ions produced by electron dissociative attachment of vibrationally excited molecules and by ionic conversion on plasma grid are self-consistently simulated. Results show the non-ambipolar character of the transport in the expansion region driven by electron magnetic drifts in the plane perpendicular to the filter field. It induces a top-bottom asymmetry detected up to the extraction grid which in turn leads to a tilted positive ion flow hitting the plasma grid and a tilted negative ion flow emitted from the plasma grid. As a consequence, the plasma structure is not uniform around the single aperture: the meniscus assumes a form of asymmetric lobe and a deeper potential well is detected from one side of the aperture relative to the other side. Therefore, the surfaceproduced contribution to the negative ion extraction is not equally distributed between both the sides around the aperture but it come mainly from the lower side of the grid giving an asymmetrical current distribution in the single beamlet.

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“…Different bulk collisions are implemented using Test Particle and Direct Simulation Monte Carlo Collision techniques [30]. The list of relevant collisions included are reported in [31].…”

Section: Description and Assumptions Of Numerical Modelmentioning

confidence: 99%

PIC modeling of negative ion sources for fusion

Taccogna

Minelli

2017

New J. Phys.

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“…[1][2][3][4][5][6][7][8][9][10] All the extraction region models [10][11][12][13] suffer from an important source of inconsistency: plasma injection condition from the source bulk region. In fact, in an almost collisionless sheath, there is no mechanism to redistribute the energy in parallel and perpendicular directions and therefore the plasma bulk boundary values of flow velocities are very important.…”

Section: Introductionmentioning

confidence: 99%

Negative ion extraction by particle model

Taccogna

Minelli

2013

Review of Scientific Instruments

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More self-consistent injection boundary conditions from the source region have been used in the extraction region model to examine the negative ion formation and transport. Bulk kinetic, plasma-surface, and gas-surface processes have been all included. This work represents a first example of coupling between different models, and it shows the important role of positive ion conversion on plasma grid for the extracted negative ion current.

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“…18 Other modeling approaches, such as two-dimensional fluid models and particle-in-cell simulations using Monte Carlo collision models, have been used to analyze the reaction kinetics in hydrogen plasmas. [19][20][21][22][23][24][25] In all of the aforementioned hydrogen plasma global models, the EED was assumed to be Maxwellian. Some researchers have identified that a change in the electron energy distribution function (EEDF), i.e., from a Maxwellian EEDF to a non-Maxwellian EEDF, can affect the model results.…”

Section: Introductionmentioning

confidence: 99%

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

et al. 2015

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A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the biMaxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies. V C 2015 AIP Publishing LLC. [http://dx.

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Modeling of a negative ion source. II. Plasma-gas coupling in the extraction region

Abstract: The production, destruction and transport of H -in the extraction region of a negative ion source are investigated with a 1D(z)-3V Particle-in-Cell electrostatic code. The motion of charged particles (e, H +

Cited by 33 publications

References 46 publications

PIC modeling of negative ion sources for fusion

PIC modeling of negative ion sources for fusion

Negative ion extraction by particle model

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

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