12 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 shearedmore »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 » 
FY 2016 Fusion Energy Sciences (FES) Theory and Simulation Performance Target
Annual target: Predicting the magnitude and scaling of the divertor heat load width in magnetically confined burning plasmas is a high priority for the fusion program and ITER. One of the key unresolved physics issues is what sets the heat flux width at the entrance to the divertor region. Perform massively parallel simulations using 3D edge kinetic and fluid codes to determine the parameter dependence of the heat load width at the divertor entrance and compute the divertor plate heat flux applicable to moderate particle recycling conditions. Comparisons will be made with data from DIIID, NSTXU, and CMod. 
Effect of Drift Waves on Plasma Blob Dynamics
Cited by 34 
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 
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 »