Improved elastic collision modeling in DEGAS 2 for low-temperature plasmas

Kanzleiter, R.; Stotler, D.P.; Karney, Charles F. F.; Steiner, D.

doi:10.1063/1.1321018

Cited by 22 publications

(13 citation statements)

References 23 publications

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“…The atom -ion interaction incorporates both classically identifiable charge exchange and elastic scattering channels. For computational efficiency, a minimum scattering angle is enforced with a constraint that the momentum transport cross-section be unaltered [18]. The differential scattering is handled using cumulative probability tables for the cosine of the scattering angle.…”

Section: Description Of Simulation and Baseline Resultsmentioning

confidence: 99%

Understanding of Neutral Gas Transport in the Alcator C-Mod Tokamak Divertor

Stotler¹,

Pitcher²,

Boswell³

et al. 2002

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Abstract.A series of experiments on the effect of divertor baffling on the Alcator C-Mod tokamak provides stringent tests on models of neutral gas transport in and around the divertor region. One attractive feature of these experiments is that a trial description of the background plasma can be constructed from experimental measurements using a simple model, allowing the neutral gas transport to be studied with a stand-alone code. The neutral-ion and neutral-neutral elastic scattering processes recently added to the DEGAS 2 Monte Carlo neutral transport code permit the neutral gas flow rates between the divertor and main chamber to be simulated more realistically than before. Nonetheless, the simulated neutral pressures are too low and the deuterium Balmer-α emission profiles differ qualitatively from those measured, indicating an incomplete understanding of the physical processes involved in the experiment. Some potential explanations are examined and opportunities for future exploration are highlighted. Improvements to atomic and surface physics data and models will play a role in the latter.

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Section: Description Of Simulation and Baseline Resultsmentioning

confidence: 99%

Understanding of Neutral Gas Transport in the Alcator C-Mod Tokamak Divertor

Stotler¹,

Pitcher²,

Boswell³

et al. 2002

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“…For energies < 1 eV, the differential scattering cross section is significant for a range of scattering angles, blurring the distinction between "elastic scattering" and "charge exchange". A more complicated sampling procedure would be required in this case [27].…”

Section: Treatment Of Ionization and Charge Exchangementioning

confidence: 99%

Energy Conservation Tests of a Coupled Kinetic-kinetic Plasma-neutral Transport Code

Stotler¹,

Chang²,

Ku³

et al. 2012

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Abstract. An approach to coupling two kinetic particle codes for the simulation of neutral-plasma interactions in magnetic fusion devices is described. The behavior of the neutral atoms and molecules is modeled with a Monte Carlo code. The plasma species are simulated with a particle-in-cell code that integrates the guiding center equations of motion and computes a self-consistent electric field. The coupling algorithm is designed to conserve mass in the neutral-plasma exchanges to statistical accuracy. Although energy is not fully conserved due to the velocity dependence of the charge exchange cross section and the kinetic character of both species, the impact of this non-conservation on the overall simulation is negligible.

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“…Elastic collisions were turned off, as they should only become important for cold, detached divertors [20]. We further simplify the ion inertia term as b…”

Section: Parallel Momentum Equationmentioning

confidence: 99%

Total fluid pressure imbalance in the scrape-off layer of tokamak plasmas

et al. 2017

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Abstract. Simulations using the fully kinetic neoclassical code XGCa were undertaken to explore the impact of kinetic effects on scrape-off layer (SOL) physics in DIII-D H-mode plasmas. XGCa is a total-f , gyrokinetic code which self-consistently calculates the axisymmetric electrostatic potential and plasma dynamics, and includes modules for Monte Carlo neutral transport.Previously presented XGCa results showed several noteworthy features, including large variations of ion density and pressure along field lines in the SOL, experimentally relevant levels of SOL parallel ion flow (Mach number∼0.5), skewed ion distributions near the sheath entrance leading to subsonic flow there, and elevated sheath potentials [R.M. Churchill, Nucl. Mater. & Energy, submitted].In this paper, we explore in detail the question of pressure balance in the SOL, as it was observed in the simulation that there was a large deviation from a simple total pressure balance (the sum of ion and electron static pressure plus ion inertia). It will be shown that both the contributions from the ion viscosity (driven by ion temperature anisotropy) and neutral source terms can be substantial, and should be retained in the parallel momentum equation in the SOL, but still falls short of accounting for the observed fluid pressure imbalance in the XGCa simulation results.

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Improved elastic collision modeling in DEGAS 2 for low-temperature plasmas

Cited by 22 publications

References 23 publications

Understanding of Neutral Gas Transport in the Alcator C-Mod Tokamak Divertor

Understanding of Neutral Gas Transport in the Alcator C-Mod Tokamak Divertor

Energy Conservation Tests of a Coupled Kinetic-kinetic Plasma-neutral Transport Code

Total fluid pressure imbalance in the scrape-off layer of tokamak plasmas

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