DIII-D Research to Prepare for Steady State Advanced Tokamak Power Plants

Abstract

We review progress made on the advanced tokamak path to fusion energy by the DIII-D National Fusion Facility (Luxon et al. in Nucl Fusion 42:614, 2002). The advanced tokamak represents a highly attractive approach for a future steady state fusion power plant. In this concept, there is a natural alignment between high pressure operation, favorable stability and transport properties, and a highly self-driven ('bootstrap') plasma current to sustain operation efficiently and without disruptions. Research on DIII-D has identified several promising plasma configurations for fully non-inductive operation with potential applications to a range of future devices, from ITER to nuclear science facilities, to compact or large scale fusion power plants. Significant progress has been made toward realizing these scenarios, with the demonstration of high b access, off-axis current drive techniques, model based profile control, and stability and ELM control in reactor relevant physics regimes. Radiative techniques have also been pioneered to develop improved compatibility with divertor requirements, and simultaneous access to high performance pedestals. Research has also developed major advances in physics understanding, validating concepts of kinetic damping of ideal MHD instabilities that enable high b operation, identifying how current profile and b influence plasma turbulence in order to validate and improve turbulent transport models, and understanding the physics of energetic particle redistribution due to Alfvénic and other instabilities. These advances have been partnered with development of a rigorous integrated modeling framework used to interpret and validate individual physics models of the various aspects of plasma behavior, and to guide development of improved regimes and upgrades. These tools are also being used to develop and validate concepts for future reactors directly. Having established these foundations, DIII-D is now undergoing a substantial upgrade to raise power, current drive, electron heating and 3-D field capabilities in order to validate this physics and test conceptual solutions in reactor-relevant physics regimes, with a goal to resolve the key scientific and technology questions to enable a decision on a future steady state fusion power plant.

Effects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak

“…In other words, this turbulence outside an MI can spread into the MI if its amplitude is sufficiently large 30 . In the recent DIII-D 31 and HL-2A 32 experiments 12 , 33 , 34 , observations which seem to result from the spreading of the density and temperature turbulence towards the O-point of an MI are reported. In addition, the nonlinear electrostatic gyrokinetic simulation based on the KSTAR plasma equilibrium and profiles showed that turbulence and the heat can spread into an MI which was initially stable region 35 .…”

Analysis of Electromagnetic Loads on the Vacuum Vessel during Thermal Quench in the TRT Tokamak

“…10 seems unexpected. For the force and the so-called sideways (lateral) force, the following equality is valid [53]: (16) where c is the constant vector ( to obtain the ), and the integration is performed over an axially symmetric toroidal shell that encloses the wall from the outside. At the initial time, when there are no currents in the wall, the force acting on the wall is zero, .…”

“…Here, the plasma and wall are vertically elongated, but it can be expected that the main dependencies found in [23][24][25][26] should also manifest themselves in our case too [22,31,32]. In particular, we will check the prediction that a strong radial force can be generated during the TQ before the CQ start, although the presence of dangerous electromagnetic loads in tokamaks is usually associated with the current quench [6,7,[11][12][13][14][15][16][17][18][19][33][34][35][36][37][38][39][40][41][42][43][44], sometimes explicitly noting that the force is proportional to [7,36,42].…”

“…In fact, the beta values are at the level of a few percent (less than 3% in the TRT project), but they are called high because of dangerous vicinity to the limits, exceeding which results in the development of instabilities. The stability problems still remain critical for the toroidal systems [6][7][8][9][10], although the considerable progress has been achieved in tokamak studies [6,7,[11][12][13][14][15][16]. However, with increasing scales of experiments, new problems arise, because the instabilitygenerated releases of heat and magnetic energy result in damage of the wall and in-vessel elements.…”

“…However, with increasing scales of experiments, new problems arise, because the instabilitygenerated releases of heat and magnetic energy result in damage of the wall and in-vessel elements. The most dangerous are disruptions [6,7,[11][12][13][14][15][16][17][18][19], which are almost impossible to avoid when operating in the intensive tokamak regimes. Analysis of the pulsed loads during the disruptions becomes a necessity.…”