Elementary Processes in Hydrogen-Helium Plasmas

Janev, R. K.; Langer, W. D.; Post, D.; Evans, K.

doi:10.1007/978-3-642-71935-6

Cited by 675 publications

(516 citation statements)

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“…Removing these electrons is necessary to reduce the destruction of negative ions which occurs mainly by electron stripping and mutual neutralization with H + . While the probability for electron stripping decreases rapidly with decreasing electron temperature for T e <10 eV [3], mutual neutralization is almost independent of the electron temperature. The rate coefficients for both processes are equal at T e =2 eV, thus the destruction of H − is minimized for T e <2 eV.…”

Section: Introductionmentioning

confidence: 94%

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Wünderlich

Gutser

Fantz

2007

AIP Conference Proceedings

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Abstract. The development of a RF driven negative-ion source currently in progress at IPP Garching has made remarkable progresses during the last years. Optimization of the source strongly depends on the understanding of the physics of generation, destruction and extraction of negative ions. Numerical model calculations can provide important information needed for the improvement of this understanding. Since negative ions are mainly produced on Cesium covered surfaces of the source, and have a survival length in the range of a few cm, models for the region close to the plasma grid are of particular interest. The plasma in this region is affected by magnetic filter fields. Another important feature is biasing of the plasma grid which strongly influences the co-extracted electron current. The different effects are treated in two separate models. Their current status is presented: a particle-in-cell-code (PIC) is used to study the influence of filter fields and bias voltage on the plasma flow onto the plasma grid. The motion of the charged particles due to their own and externally applied electric field is simulated in a selfconsistent way. In the second code the survival probability of negative ions produced on the surface of the plasma grid is estimated using test-particles. The Monte-Carlo technique is applied for the treatment of inelastic and elastic collisions.

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Section: Introductionmentioning

confidence: 94%

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Wünderlich

Gutser

Fantz

2007

AIP Conference Proceedings

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“…where x is along the magnetic field line, pi,e are the ion and electron static pressures (T = Te assumed), m is the ion mass, n and v are the plasma 2 density and velocity, vH is the neutral velocity and Sm = nnH(ov)m is the charge-exchange reaction rate [5]. We assume for simplicity that only atoms are present (no molecules).…”

Section: Simple Modelmentioning

confidence: 99%

The role of friction in SOL pressure balance in Alcator C-Mod

Pitcher

Goetz

LaBombard

et al. 1999

Journal of Nuclear Materials

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We assess the importance of ion-neutral friction in parallel plasma pressure balance in Alcator C-Mod. For a high-powered N 2 seeded case, a large parallel field plasma pressure drop is observed, coincident with a significant velocity differential between the plasma ions and the neutral particles in the divertor. The observed pressure loss is consistent with the inferred friction and cannot be explained by volume recombination.

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“…The densities and parallel fluxes of singly-and doubly-ionized 3 He are inferred at the sheath edge of the entrance slit (Section II).…”

Section: Introductionmentioning

confidence: 99%

Helium-3 transport experiments in the scrape-off layer with the Alcator C-Mod omegatron ion mass spectrometer

Nachtrieb

LaBombard

2000

Physics of Plasmas

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Abstract3 He gas was puffed from the wall into ohmic L-mode discharges of the Alcator C-Mod tokamak and the charged states were measured near the wall with the omegatron ion mass spectrometer. Analysis of the data shows that the concentrations of singly-and doubly-ionized helium near the wall are approximately equal. The electron temperature and density at the omegatron are too low to account for ionization of helium in the local flux tube, therefore the helium is ionized in a hotter region of the edge plasma and is transported to the omegatron. A simple one-dimensional radial transport model reproduces the observed values of charge state flux and density, but only if rapid cross-field transport is included, increasing with distance from the separatrix.A constant cross-field diffusion coefficient of order 2 m 2 /s and an outward convection velocity profile increasing to of order 100 m/s in the far scrape-off layer is implied.

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Elementary Processes in Hydrogen-Helium Plasmas

Cited by 675 publications

References 0 publications

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

Influence of Magnetic Fields and Biasing on the Plasma of a RF Driven Negative Ion Source

The role of friction in SOL pressure balance in Alcator C-Mod

Helium-3 transport experiments in the scrape-off layer with the Alcator C-Mod omegatron ion mass spectrometer

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