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Showing 1 to 20 of 24 for “"Scrape-Off Layer"”.
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Plasma flows in the Alcator C-Mod scrape-off layer
… plasma flows are persistently observed in the scrape-off layer (SOL) of tokamaks, at locations far from material surfaces. Ballooning-like transport asymmetries are thought to be a principal driver for the strong parallel flows, a hypothesis supported by the observation of steep high-field side …
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Turbulence and transport phenomena in edge and scrape-off-layer plasmas
… design is optimized for the study of edge and scrape-off-layer turbulence, based on previous studies of these regions. Analysis of the data from this diagnostic in Ohmic L-modes from the electron diamagnetic drift propagating turbulence in the closed field line region of the plasma edge shows a …
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Behavior of lower hybrid waves in the scrape off layer of a diverted tokamak
… of Lower Hybrid (LH) waves in the edge and Scrape Off Layer (SOL) of Alcator C-Mod, a compact, high field, high density, diverted tokamak. The results of coupling experiments over a range of plasma parameters in both Land H-mode plasmas are presented. Experimental observations suggest that …
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Measurements of divertor target plate conditions and their relationship to scrape-off layer transport
Cross-field filamentary transport in the scrape-off layer (SOL) is important for controlling SOL profiles, main-chamber recycling fluxes, and divertor operation. However, questions remain about the extent to which divertor target conditions play a role in setting transport levels. The Alcator C-Mod …
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Local gas injection as a scrape-off layer diagnostic on the Alcator C-mod tokamak
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1996.
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Impact of wave-filament scattering in the scrape-off layer during lower hybrid current drive
… by turbulent density fluctuations in the scrape-off layer (SOL), which is hypothesized to be the reason for poor agreement between LHCD experiments and simulations (which do not account for scattering). This thesis investigates the impact of scattering processes on LHCD, and attempts to …
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Study of High Harmonic Fast Waves Interactions in the Scrape off Layer of NSTX-U
… to 60% of the injected power can be lost in the Scrape-Off Layer (SOL) when the fast wave is able to propagate in front of the antenna [Hosea, Phys. Plasmas 15, 056104 (2008))]. This work discusses progress in modeling HHFW propagation and losses in the divertor region using more realistic SOL …
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Investigation of plasma potential enhancement in the scrape-off layer of ion cyclotron range of frequencies heated discharges on Alcator C-Mod
ICRF-heated discharges on Alcator C-Mod are associated with enhanced sputtering of molybdenum plasma facing surfaces and increased levels of core impurity contents, which subsequently degrade the core plasma performance. RF sheath rectification on open magnetic field lines that intercept material …
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Studies of plasma potential measurements using an ion-sensistive probe
The plasma potential of the scrape-off-layer (SOL) in the tokamak is a key indicator of the erosion rate of the plasma facing component (PFC) material. The Alcator C-Mod SOL plasma potential is currently measured by emissive probes, which is an established potential diagnostic, yet the probes are …
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Discontinuous Galerkin modeling of plasma turbulence in a simple magnetized torus
… is a good model of the plasma turbulence in the scrape-off layer (SOL) region of tokamaks or other fusion devices. This region lies outside the last closed magnetic flux surface and plays an important role in determining the exhaust of particles and heat, as well as setting conditions in the core …
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Visible spectroscopic imaging on the Alcator C-Mod tokamak
… on a poloidal temperature gradient in the outer scrape-off-layer. 2) A camera viewing the inner wall tangentially was used to measure Da emission profiles. A sharp break in slope of the radial density profile was found at the location of the secondary separatrix near the inner wall by using these …
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Physics and application of impurity plume dispersal as an edge plasma flow diagnostic on the Alcator C-Mod tokamak
… ethylene, C₂D₄) is injected locally into the scrape-off layer (SOL) through the end of a reciprocating fast-scanning probe, and the resultant emission ("plume") is imaged from two near-perpendicular views. Plumes are generated at various SOL depths, while views are obtained using coherent …
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A Multi-Region Multi-Timescale Burning Plasma Dynamics Model for Tokamaks
… in tokamaks. Regions including the core, edge, scrape-off layer, and divertor are modeled as separate nodes. Fusion alpha heating with a time delay between heating electrons and ions is considered. Ohmic and auxiliary heating methods are included. Radiations such as electron cyclotron radiation, …
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Improved performance of the hPIC particle-in-cell code by incorporating a new non-uniform implicit mesh based on the PUMI infrastructure
… at capturing the high plasma gradients in a Scrape-Off-Layer (SOL). Especially in the magnetic and electrostatic sheaths forming in front of the material surfaces. The hPIC Particle In Cell code developed previously at UIUC has been modified to incorporate a new implicit, parameterized, …
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Characterisation of Detached Plasmas on the MAST Tokamak
… the dominant mechanisms governing parallel scrape-off layer transport including flux expansion, dynamic viscosity and cross-field drift motion in attached conditions. It has been found that the invocation of flux expansion, parallel viscosity and diamagnetic drift motion assist the OSM …
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Effects of RF power on SOL density profiles and RF coupling on the Alcator C-Mod tokamak
… (ICRF) antenna has been used to measure the scrape-off-layer (SOL) density profiles under a wide range of plasma parameters in order to study plasma-antenna coupling and non-linear RF-SOL interactions on Alcator C-Mod. After validating the reflectometer density profiles with other density …
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Whole-device modeling of HIDRA plasmas for experimental planning
… confined core and (2) the unconfined Scrape-Off-Layer (SOL). The core is modeled using 1-dimensional (radial) particle and energy diffusion equations with a Bohm diffusivity. The primary innovation made here for the core analysis is a way to solve the diffusion equations without …
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Studies of Edge Fluctuations of Negative Triangularity Plasma on TCV using a New Gas-Puff Imaging Diagnostic
… structures (elongated along the field) in the scrape-off layer (SOL). Estimation of the size, speed, and frequency of blobs allows evaluation of particle fluxes leaving the magnetically confined plasma boundary. Traditional approaches to blob analysis in the GPI images, including conditional …
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The effect of ICRF and LHCD waveguide and launcher location on tritium breeding ratio and radiation damage in fusion reactors
… for better wave penetration, and has favorable scrape-off-layer and plasma material interaction characteristics [4]. However the poloidal location and size of RF launchers will also affect important aspects of the neutronics of the tokamak fusion design, i.e. how the 14.1 MeV neutrons born out …
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Detection of lower hybrid waves at the plasma edge of a diverted tokamak
… electrostatic lower hybrid (LH) waves in the scrape-off layer (SOL), where a significant amount of the injected LH power may be deposited due to a number edge loss mechanisms. An existing ordinary-mode (O-mode) reflectometer system has been modified to measure the backscattered O-mode wave as …
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