For Plasma with a Hot Core and Cool Edges, Super-H Mode Shows Promise

Fusion reactors face a challenge called “core-edge integration,” which involves maintaining a plasma that is hot at the core but not too hot to damage reactor walls. New research finds that a previously identified operating regime called Super H-mode can leverage the use of impurities such as nitrogen to address this challenge. The research also indicates that Super-H mode can be scaled up to future fusion plants.

Researchers Stick Out Their Necks to Understand How Fusion Plasmas Fuel Up

The nuclei that smash together to produce fusion energy in a reactor originate from ionized neutral particles. The edges of fusion devices have large numbers of neutrals available to gain or lose electrons to become ions. These neutrals influence several important features of the plasma, including the rate at which the plasma fuels a reactor. A new pinhole camera system called Lyman-alpha Measurement Apparatus (LLAMA) on the DIII-D tokamak helped researchers better understand these neutrals.

U.S. Researchers Simulate Compact Fusion Power Plant Concept

The Compact Advanced Tokamak (CAT) concept uses physics models to show that by carefully shaping the plasma and the distribution of current in the plasma, fusion plant operators can suppress turbulent eddies in the plasma. This would reduce heat loss and allow more efficient reactor operation. This advance could help achieve self-sustaining plasma and smaller, less expensive power plants.

Imposing Chaos on Magnetic Fields Suppresses Runaway Electrons in a Fusion Plasma

Researchers are using smaller tokamaks and computer models to test approaches for suppressing runaway electrons. This research used measurements and modeling to demonstrate that perturbations to the magnetic field in a tokamak fusion plasma can suppress high-energy runaway electrons. The results could help improve the operation of ITER and other future fusion devices.

Negative Triangularity—a Positive for Tokamak Fusion Reactors

In a conventional tokamak, the cross-section of the plasma is shaped like the letter D. Facing the straight part of the D on the inside side of the donut-shaped tokamak is called positive triangularity. New research suggests that reversing the plasma—negative triangularity–reduces how much the plasma interacts with the surfaces of the tokamak for reduced wear.

Scientists Solve Key Challenge for Controlling “Runaway” Electrons in Fusion Plasmas

Scientists at the DIII-D National Fusion Facility have for the first time studied the internal structure and stability of high-energy runaway electron (RE) beams in a tokamak. The finding could provide a way to control the damaging potential of RE beams and could contribute to future power production using tokamak fusion power plants.

Magnetic Ripples Calm the Surface of Fusion Plasmas

The ITER fusion reactor being built in the south of France will use rippled magnetic fields to prevent bursts of heat and particles that can damage the walls of the reactor. Now, physicists at the Princeton Plasma Physics Laboratory and the DIII-D national fusion facility have compared computer simulations of the DIII-D plasma with experimental measurements to better understand how controlled magnetic ripples outside the plasma can suppress these bursts.

DIII-D Researchers Use Machine Learning to Steer Fusion Plasmas Near Operational Limits

Researchers at the DIII-D National Fusion Facility recently achieved a scientific first when they used machine learning calculations to automatically prevent fusion plasma disruptions in real time, while simultaneously optimizing the plasma for peak performance. The new experiments are the first of what they expect to be a wave of research in which machine learning–augmented controls could broaden the understanding of fusion plasmas. The work may help deliver reliable, peak-performance operation of future fusion reactors.