Research at the DIII-D National Fusion Facility
Research at DIII-D
The DIII-D tokamak is an experimental fusion device that seeks to discover the underlying physics needed to confidently project solutions to a fusion power reactor; this device has the unique advantages of notable flexibility to rapidly pioneer innovative solutions and world-leading measurement and investigative capabilities to support on-going and future research efforts.
The mission of the DIII-D research program is to pioneer the plasma solutions, technologies, scientific basis and operational approach, and to enable the development of the people needed to make fusion energy a reality. The overall program is guided by the 5-year plan approved by the DOE Office of Science Fusion Energy Sciences program, which sets the research milestones and priorities of the program. Run time is allotted based on double-blinded peer review of project proposals that fit the current research priorities. Furthermore, to support workforce development, a portion of the total runtime is allotted for graduate student projects each year.
Research Division Organization and Goals
The DIII-D Research Division is divided into 3 groups: Fusion Pilot Plant Research, Plasma-Interacting Technology, and ITER Research.
Fusion Pilot Plant (FPP) Research group
Topical areas: Steady-state and pulsed fusion core, Plasma control, Divertor science and innovation, Core-edge integration
The FPP group focuses on identifying attractive options for tokamak pilot plants, supporting the development of both steady-state and pulsed operations. Steady-state operation will rely on achieving full non-inductive sustainment of the plasma current by external current drive and self-driven bootstrap current at high plasma pressure, while pulsed operation can benefit from non-inductive current drive but typically relies on higher plasma current dominated by inductive drive. Additionally, the high heat and particle exhaust coming out of the plasma core must be adequately managed to protect material surfaces from damage and control plasma density and dilution. Thus, in the FPP group, the physics of integrating core scenario design and boundary/divertor development will be given special attention, as a tension exists between design choices that maximize core performance and choices that best manage boundary heat and particle exhaust. Key to all of these efforts is the controls research in the group, while will involve multiple tools (i.e., full and reduced physics model-based tools and data-driven tools including machine learning/artificial intelligence) to tackle multiple problems, from core tearing mode avoidance to real-time divertor detachment. Thus, the research goals of the group are:
- Develop integrated operational scenarios for sustaining high fusion power and fusion gain either indefinitely or in pulses, with all scenarios achieving sufficient MHD stability and energy confinement
- Design of optimal divertor magnetic and structural geometries that enable high plasma shaping (for high core performance), control of scrape-off-layer magnetic flux expansion, and baffling for controlling neutral trapping, impurity radiation density, particle pumping, and target heat flux through divertor detachment
- Develop and deploy advanced plasma controls, both to achieve DIII-D’s FPP physics research objectives and to provide useful controls for FPPs that will have different limitations than present-day devices
ITER Research group
Topical areas: ITER integrated scenarios, Turbulence and transport, Energetic particles and Alfvén eigenmodes, Pedestal and non/small-ELM regimes, Transient control
The ITER tokamak experiment, currently under construction in southern France through an international research collaboration, seeks to demonstrate the scientific and technical feasibility of fusion energy. A central goal of the ITER project is to achieve a fusion gain ratio of Q (output fusion power to input power)=10 or higher for an extended duration of hundreds of seconds and a “steady state” gain of Q (output fusion power to input power)=5 for potentially thousands of seconds. The newly formed ITER Research Group at DIII-D aims to make ITER successful by developing operational scenarios, validating simulations used to predict ITER confinement and pressure, and further optimizing its performance. The research goals of the topical areas are:
- Develop and test ITER-like plasmas to understand performance and stability limits, radiative properties, core-edge integration
- Identify the properties and dynamics of transport of fuel particles, impurities, energy, and momentum across magnetic fields and predicting intrinsic rotation
- Predict the behavior of the fusion-produced energetic alpha particle population, other fast particles, and Alfvénic instability generation
- Understand the mechanisms and dynamics of the edge pedestal that forms the boundary between the hot plasma core and the boundary plasma layer
- Develop and validate approaches to control, reduce and suppress transient instabilities that can potentially damage walls due to high heat and particle bursts
Plasma-Interacting Technology (PIT) group
Topical areas: Plasma-material interactions, Disruption mitigation, Heating and current drive, Diagnostics and actuators
As the U.S. fusion energy program works to resolve the design of a low capital cost FPP, with a goal to start engineering design and possibly construction in the next decade, there is a much greater focus on solving the technological challenges needed to realize an FPP. A key aspect of this development lies in assessing FPP technology in the plasma environment, where plasma interaction can be a key constraint or is a key point of that technology. To meet this challenge, the DIII-D PIT group is focused on key technology areas where DIII-D can have the biggest impact on the FPP program, such as generating input for trade studies leading to FPP designs. Key goals for the PIT group include:
- Assess current and novel diagnostic and actuator techniques for robust plasma control and machine protection in a high neutron fluence environment, and establish capability to validate such techniques
- Optimize heating and current driver systems to achieve net electrical power generation, with a focus on experimentally testing and validating models of helicon, lower hybrid, and electron cyclotron technologies
- Develop and validate methods to suppress and mitigate runaway electrons, as well as passive and alternative mitigation systems, to reduce the risk of unplanned and long-duration maintenance periods
- Experimentally validate plasma-material interactions for optimizing the design of the FPP first wall and divertor, including dust/debris management, to maximize component lifetime and minimize fuel retention
Run time is also regularly allotted for Frontier Sciences. This initiative exploits DIII-D’s unique parameter access and innovative and extensive diagnostics to support the wider frontier plasma science community. Frontier Science projects complement, extend or augment work on plasma physics phenomena, enabling key tests of theories and answering important frontier-related questions, as the different applications of plasma physics share common foundations on questions such as magnetic reconnection, wave-particle interactions, particle energization, and global MHD stability. The DIII-D facility, which mainly targets fusion energy goals, can provide a window into these fundamental processes that complement capabilities elsewhere. Using DIII-D to develop a deeper understanding of basic plasma physics phenomena can also stimulate new thinking and innovation within both the fusion and fundamental plasma physics communities. Future calls for proposals for Frontier Sciences projects can be found here.