2,934 research outputs found
Towards Real-Time Detection and Tracking of Spatio-Temporal Features: Blob-Filaments in Fusion Plasma
A novel algorithm and implementation of real-time identification and tracking
of blob-filaments in fusion reactor data is presented. Similar spatio-temporal
features are important in many other applications, for example, ignition
kernels in combustion and tumor cells in a medical image. This work presents an
approach for extracting these features by dividing the overall task into three
steps: local identification of feature cells, grouping feature cells into
extended feature, and tracking movement of feature through overlapping in
space. Through our extensive work in parallelization, we demonstrate that this
approach can effectively make use of a large number of compute nodes to detect
and track blob-filaments in real time in fusion plasma. On a set of 30GB fusion
simulation data, we observed linear speedup on 1024 processes and completed
blob detection in less than three milliseconds using Edison, a Cray XC30 system
at NERSC.Comment: 14 pages, 40 figure
Interrelationship between Lab, Space, Astrophysical, Magnetic Fusion, and Inertial Fusion Plasma Experiments
The objectives of this review are to articulate geospace, heliospheric, and astrophysical plasma physics issues that are addressable by laboratory experiments, to convey the wide range of laboratory experiments involved in this interdisciplinary alliance, and to illustrate how lab experiments on the centimeter or meter scale can develop, through the intermediary of a computer simulation, physically credible scaling of physical processes taking place in a distant part of the universe over enormous length scales. The space physics motivation of laboratory investigations and the scaling of laboratory plasma parameters to space plasma conditions, having expanded to magnetic fusion and inertial fusion experiments, are discussed. Examples demonstrating how laboratory experiments develop physical insight, validate or invalidate theoretical models, discover unexpected behavior, and establish observational signatures for the space community are presented. The various device configurations found in space-related laboratory investigations are outlined
Research briefing on contemporary problems in plasma science
An overview is presented of the broad perspective of all plasma science. Detailed discussions are given of scientific opportunities in various subdisciplines of plasma science. The first subdiscipline to be discussed is the area where the contemporary applications of plasma science are the most widespread, low temperature plasma science. Opportunities for new research and technology development that have emerged as byproducts of research in magnetic and inertial fusion are then highlighted. Then follows a discussion of new opportunities in ultrafast plasma science opened up by recent developments in laser and particle beam technology. Next, research that uses smaller scale facilities is discussed, first discussing non-neutral plasmas, and then the area of basic plasma experiments. Discussions of analytic theory and computational plasma physics and of space and astrophysical plasma physics are then presented
Neoclassical flows in deuterium-helium plasma density pedestals
In tokamak transport barriers, the radial scale of profile variations can be
comparable to a typical ion orbit width, which makes the coupling of the
distribution function across flux surfaces important in the collisional
dynamics. We use the radially global steady-state neoclassical {\delta}f code
Perfect to calculate poloidal and toroidal flows, and radial fluxes, in the
pedestal. In particular, we have studied the changes in these quantities as the
plasma composition is changed from a deuterium bulk species with a helium
impurity to a helium bulk with a deuterium impurity, under specific profile
similarity assumptions. The poloidally resolved radial fluxes are not
divergence-free in isolation in the presence of sharp radial profile
variations, which leads to the appearance of poloidal return-flows. These flows
exhibit a complex radial-poloidal structure that extends several orbit widths
into the core and is sensitive to abrupt radial changes in the ion temperature
gradient. We find that a sizable neoclassical toroidal angular momentum
transport can arise in the radially global theory, in contrast to the local.Comment: 14 pages, 19 figure
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