11 Search Results

Analytical and numerical study of the transverse KelvinHelmholtz instability in tokamak edge plasmas
Sheared flows perpendicular to the magnetic field can be driven by the Reynolds stress or ion pressure gradient effects and can potentially influence the stability and turbulent saturation level of edge plasma modes. On the other hand, such flows are subject to the transverse Kelvin Helmholtz (KH) instability. Here, the linear theory of KH instabilities is first addressed with an analytic model in the asymptotic limit of long wavelengths compared with the flow scale length. The analytic model treats sheared ExB flows, ion diamagnetism (including gyroviscous terms), density gradients and parallel currents in a slab geometry, enabling a unified summarymore »Cited by 1 
Comparison of 2D simulations of detached divertor plasmas with divertor Thomson measurements in the DIIID tokamak
A modeling study is reported using new 2D data from DIIID tokamak divertor plasmas and improved 2D transport model that includes large crossfield drifts for the numerically difficult Hmode regime. The data set, which spans a range of plasmas densities for both forward and reverse toroidal magnetic field (B _{t}) over a range of plasma densities, is provided by divertor Thomson scattering (DTS). Measurements utilizing Xpoint sweeping give corresponding 2D profiles of electron temperature (T _{e}) and density (n _{e}) across both divertor legs for individual discharges. The calculations show the same features of in/out plasma asymmetries as measured inmore » 
Electromagnetic effects on dynamics of highbeta filamentary structures
The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded highbeta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner scrapeoff layer (SOL) region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and BOUT++more » 
Electromagnetic effects on dynamics of highbeta filamentary structures
The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded highbeta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner SOL region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and the BOUT++ simulation,more »Cited by 5 
Effect of Drift Waves on Plasma Blob Dynamics
Cited by 34 
Modeling of large amplitude plasma blobs in threedimensions
Fluctuations in fusion boundary and similar plasmas often have the form of filamentary structures, or blobs, that convectively propagate radially. This may lead to the degradation of plasma facing components as well as plasma confinement. Theoretical analysis of plasma blobs usually takes advantage of the socalled Boussinesq approximation of the potential vorticity equation, which greatly simplifies the treatment analytically and numerically. This approximation is only strictly justified when the blob density amplitude is small with respect to that of the background plasma. However, this is not the case for typical plasma blobs in the far scrapeoff layer region, where themore » 
Fusion Energy Sciences Exascale Requirements Review. An Office of Science review sponsored jointly by Advanced Scientific Computing Research and Fusion Energy Sciences, January 2729, 2016, Gaithersburg, Maryland
The additional computing power offered by the planned exascale facilities could be transformational across the spectrum of plasma and fusion research — provided that the new architectures can be efficiently applied to our problem space. The collaboration that will be required to succeed should be viewed as an opportunity to identify and exploit crossdisciplinary synergies. To assess the opportunities and requirements as part of the development of an overall strategy for computing in the exascale era, the Exascale Requirements Review meeting of the Fusion Energy Sciences (FES) community was convened January 27–29, 2016, with participation from a broad range ofmore » 
Effects of parallel electron dynamics on plasma blob transport
The 3D effects on sheath connected plasma blobs that result from parallel electron dynamics are studied by allowing for the variation of blob density and potential along the magnetic field line and using collisional Ohm's law to model the parallel current density. The parallel current density from linear sheath theory, typically used in the 2D model, is implemented as parallel boundary conditions. This model includes electrostatic 3D effects, such as resistive drift waves and blob spinning, while retaining all of the fundamental 2D physics of sheath connected plasma blobs. If the growth time of unstable drift waves is comparable tomore »