M. Umansky
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View article: On transport of electrons in a magnetized plasma sheath
On transport of electrons in a magnetized plasma sheath Open
Electron trajectories are analyzed in the plasma sheath region in a magnetic field that intersects the surface at a shallow angle. Depending on the size of the Debye width relative to the electron gyroradius, λD/ρe, an electron either drif…
View article: Simulations of the churning mode: Toroidally symmetric plasma convection and turbulence around the X-points in a snowflake divertor
Simulations of the churning mode: Toroidally symmetric plasma convection and turbulence around the X-points in a snowflake divertor Open
Using a reduced MHD model, extended to include field-aligned thermal conduction, we present numerical simulations of the churning mode (CM): a toroidally symmetric, non-linear plasma vortex in the vicinity of the null points in a snowflake…
View article: Implicit full-F simulations of neoclassical ion transport
Implicit full-F simulations of neoclassical ion transport Open
The development of implicit time integration capabilities for axisymmetric full-F continuum simulations of ion neoclassical transport is reported. The approach involves the implicit treatment of the gyrokinetic Vlasov equation coupled to t…
View article: Semi-Implicit Continuum Kinetic Modeling of Weakly Collisional Parallel Transport in a Magnetic Mirror
Semi-Implicit Continuum Kinetic Modeling of Weakly Collisional Parallel Transport in a Magnetic Mirror Open
We present implicit-explicit (IMEX) kinetic simulations of weakly collisional parallel plasma transport in magnetic mirror configurations using the continuum code \textsc{COGENT}. The numerical scheme employs a Jacobian-free Newton--Krylov…
View article: Statistical inference of anomalous thermal transport with uncertainty quantification for interpretive 2-D SOL models
Statistical inference of anomalous thermal transport with uncertainty quantification for interpretive 2-D SOL models Open
The critical task of inferring anomalous cross-field transport coefficients is addressed in simulations of boundary plasmas with fluid models. A workflow for parameter inference in the UEDGE fluid code is developed using Bayesian optimizat…
View article: Simulations of the churning mode: toroidally symmetric plasma convection and turbulence around the X-points in a snowflake divertor
Simulations of the churning mode: toroidally symmetric plasma convection and turbulence around the X-points in a snowflake divertor Open
Using a reduced MHD model, extended to include field-aligned thermal conduction, we present numerical simulations of the churning mode (CM): a toroidally symmetric, non-linear plasma vortex in the vicinity of the null points in a snowflake…
View article: Coupling fluid plasma and kinetic neutral models using correlated Monte Carlo methods
Coupling fluid plasma and kinetic neutral models using correlated Monte Carlo methods Open
While boundary plasmas in present-day tokamaks generally fall in a fluid regime, neutral species near the boundary often require kinetic models due to long mean-free-paths compared to characteristic spatial scales in the region. Monte-Carl…
View article: Boundary plasma studies for a spherical tokamak with lithium walls
Boundary plasma studies for a spherical tokamak with lithium walls Open
Boundary plasma and plasma-material interactions are investigated for magnetised target fusion (MTF) applications. The General Fusion magnetised target fusion technology uses coaxial helicity injection (CHI) start-up which forms a spherica…
View article: Analysis of high-field side plasma instabilities in tokamak edge
Analysis of high-field side plasma instabilities in tokamak edge Open
Balanced double-null configurations are of general interest for boundary plasma physics, and they have been proposed for some future designs. Experimental observations demonstrate absence of plasma fluctuations in tokamak high-field side s…
View article: Coupling Fluid Plasma and Kinetic Neutral Models using Correlated Monte Carlo Methods
Coupling Fluid Plasma and Kinetic Neutral Models using Correlated Monte Carlo Methods Open
While boundary plasmas in present-day tokamaks generally fall in a fluid regime, neutral species near the boundary often require kinetic models due to long mean-free-paths compared to characteristic spatial scales in the region. Monte-Carl…
View article: Modeling transient edge plasma transport with dynamic recycling
Modeling transient edge plasma transport with dynamic recycling Open
The work presents numerical simulation studies of the role that dynamic plasma recycling on the main wall and divertor target surfaces plays in transient edge plasma transport phenomena, such as edge localized modes (ELMs). The studies are…
View article: Simulations of tokamak edge plasma turbulent fluctuations based on a minimal 3D model
Simulations of tokamak edge plasma turbulent fluctuations based on a minimal 3D model Open
A new simulation model for tokamak boundary plasma, SOLT3D, is implemented in the BOUT++ framework (Dudson et al 2009 Comput. Phys. Commun. 180 1467). The simulation model includes a set of dynamic equations describing collisional boundary…
View article: Novel SOLPS-ITER simulations of X-point target and snowflake divertors
Novel SOLPS-ITER simulations of X-point target and snowflake divertors Open
The design and understanding of alternative divertor configurations may be crucial for achieving acceptable steady-state heat and particle material loads for magnetic confinement fusion reactors. Multiple X-point alternative divertor geome…
View article: Ion temperature anisotropy model with cross‐field drifts in the scrape‐off layer
Ion temperature anisotropy model with cross‐field drifts in the scrape‐off layer Open
An ion temperature anisotropy model including cross‐field drifts has been implemented in the 2D transport code UEDGE. Two ion temperature equations are solved in the model to give separate ion temperatures perpendicular and parallel to the…
View article: Modelling of edge plasma dynamics with active wall boundary conditions
Modelling of edge plasma dynamics with active wall boundary conditions Open
A self‐consistent 2D model is presented for transport in boundary plasma and plasma‐facing material walls. Plasma dynamics in the domain is represented by a 2D collisional plasma fluid model in the edge‐plasma code UEDGE (Rognlien et al., …
View article: INGRID: An interactive grid generator for 2D edge plasma modeling
INGRID: An interactive grid generator for 2D edge plasma modeling Open
A fusion boundary-plasma domain is defined by axisymmetric magnetic surfaces where the geometry is often complicated by the presence of one or more X-points; and modeling boundary plasmas usually relies on computational grids that account …
View article: Modeling snowflake divertors in MAST-U Tokamak
Modeling snowflake divertors in MAST-U Tokamak Open
In a snowflake (SF) divertor, two magnetic field nulls are placed close to each other, creating four strike points (SPs) compared to two in a standard X -point divertor. In preparation for MAST-U experiments, magnetic configurations with t…
View article: Simulation of the SPARC plasma boundary with the UEDGE code
Simulation of the SPARC plasma boundary with the UEDGE code Open
Here in this work, the UEDGE edge transport code is used to examine conditions in the SPARC divertor and edge plasma for various levels of carbon impurity and power from the core (PSOL). A double-null magnetic configuration is simulated as…
View article: Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks
Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks Open
The edge-plasma profiles and fluxes to the divertor and walls of a divertor tokamak with a magnetic X-point are simulated by coupling a 2D transport code (UEDGE) and a 3D turbulence code (BOUT). An relaxed iterative coupling scheme is used…
View article: Dependence of the damage in optical metal/dielectric coatings on the energy of ions in irradiation experiments for space qualification
Dependence of the damage in optical metal/dielectric coatings on the energy of ions in irradiation experiments for space qualification Open
Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a $$\hbox {TiO}_2$$ /Al bi-layer coating has be…
View article: Damage to Relativistic Interstellar Spacecraft by ISM Impact Gas Accumulation
Damage to Relativistic Interstellar Spacecraft by ISM Impact Gas Accumulation Open
As part of the NASA Starlight collaboration, we look at the implications of impacts with the interstellar medium (ISM) on a directed energy-driven relativistic spacecraft. The spacecraft experiences a stream of MeV/nucleon impacts along th…
View article: Outer midplane neutral density measurements and H-mode fueling studies in NSTX-U
Outer midplane neutral density measurements and H-mode fueling studies in NSTX-U Open
Neutral density profiles are measured on the outboard midplane of the National Spherical Torus Experiment Upgrade (NSTX-U) using a two dimensional camera (ENDD, edge neutral density diagnostic) filtered for deuterium Balmer α (D α ) emissi…
View article: Study of passively stable, fully detached divertor plasma regimes attained in innovative long-legged divertor configurations
Study of passively stable, fully detached divertor plasma regimes attained in innovative long-legged divertor configurations Open
Numerical modeling of divertor configurations with radially or vertically extended, tightly baffled, outer divertor legs has demonstrated the existence of a passively-stable fully detached divertor regime. In the simulations, long-legged d…
View article: BOUT++ v4.3.2
BOUT++ v4.3.2 Open
BOUT++ is a framework for writing fluid and plasma simulations in curvilinear geometry. It is intended to be quite modular, with a variety of numerical methods and time-integration solvers available. BOUT++ is primarily designed and tested…