DoE Early Career Award
Starting in July 2015: Early Career Award of the Department of Energy
Title: “Plasma Material Interaction with Three-Dimensional Boundaries”
Official Announcement: http://science.energy.gov/early-career
The quest to understand the interaction of a high temperature plasma and its surrounding material surfaces is one of the key challenges on the path to harness fusion power as a new, fundamental energy source. This challenge typically involves the goal of achieving high density, low temperature (detached) plasmas close to magnetic field divertor target plates as well as understanding the plasma material interactions (PMI) in this regime. This area of research involves studying physical processes at spatial scales from nanometers to meters in all states of matter and across a broad range of energies.
New modeling capabilities, which help interpret data from current experiments and enable extrapolation to future devices, are required. This is particularly true for toroidal magnetic confinement devices with three?dimensional (3D) plasma boundaries such as tokamak devices when perturbing external magnetic fields are applied and for stellarators with an inherent 3D plasma configuration.
The goal of this research is to examine and assess the impact of 3D plasma boundaries on PMI in combination with detached plasma regimes. A critical element will be to experimentally identify critical common and unique features of 3D boundaries as compared to axisymmetric edge plasmas. Establishing a numerical toolset to support the development of predictive capabilities for these regimes is the intended key outcome of the research project. The complexity of this scientific endeavor requires a broad approach, and this research effort will help establish a solid basis to advance understanding in this area.
Funding Information: funded by the Department of Energy, Office of Fusion Energy Science, DE-SC0013911.
Since 08-15-2014: Department of Energy Grant DE-SC0012315
Title: Control of Neutral Fueling and Helium Exhaust in NSTX-Upgrade Plasmas by Three-Dimensional Magnetic Control Fields.
Short description (public abstract):
This research targets the understanding and optimization of the physical processes that define fueling and exhaust of high temperature plasmas, which are being explored as a means to accomplish energy production by nuclear fusion. Very much like in a combustion engine, a well-controlled amount of fueling and efficient exhaust has to be realized to keep the burn media clean and at desired pressures for sustained energy production. In fusion plasma, hydrogen isotopes represent the fuel while helium is the ash (the “fusion product”) from the reaction cycle. Hydrogen is supplied from the outside into the outer boundary of the plasma. In contrast, the helium is born predominantly inside of the plasma. Hence, an efficient control mechanism for fueling and exhaust also deals with desired inward transport of fuel and outward transport of helium and impurities.
Three-dimensional magnetic fields have been used as an innovative control tool for plasma edge transport and for dedicated interaction with the neutral particle source at the surrounding wall elements. They will be employed in this research to address neutral fueling, as a particularly important topic in the spherical tokamak (ST) NSTX-Upgrade. The ST magnetic confinement concept offers more stable, high performance plasma operation at reduced system size. It therefore is an attractive candidate for compact fusion energy development facilities. However, the concept so far suffers from weak plasma density control, which limits the plasma regimes accomplished as well as the duration of an experiment pulse. This research aims on exploring if dedicated density control including reduction of impurity contamination of the plasma and sufficient helium exhaust can be accomplished by use of three-dimensional magnetic control fields. The work encompasses development and validation of suitable numerical tools to gain predictive capability for future devices and reactor scale experiments.