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New discoveries about the nature of light could improve methods for heating fusion plasma

Both literally and figuratively, light pervades the world. It banishes darkness, conveys telecommunications signals between continents and makes visible the invisible, from faraway galaxies to the smallest bacterium. Light can also help heat the plasma within ring-shaped devices known as tokamaks as scientists worldwide strive to harness the fusion process to generate green electricity. Now, scientists have made discoveries about light particles known as photons that could aid the quest for fusion energy. By performing a series of mathematical calculations, the researchers found that one of a photon's basic properties is topological, meaning that it doesn't change even as the photon moves through different materials and environments.

Nuclear fusion is a powerful form of energy generation, but it has been seen as extreme and dangerous. However, this has not stopped the study and testing of fusion as a possible mid-century power solution.

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A new model for ballooning instabilities in apple-shaped fusion vessels considers the height and width of the plasma's edge.

Harnessing energy from plasma requires a precise understanding of its behavior during fusion to keep it hot, dense and stable. A new theoretical model about a plasma's edge, which can become unstable and bulge, brings the prospect of commercial fusion power closer to reality. "The model refines the thinking on stabilizing the edge of the plasma for different tokamak shapes," said Jason Parisi, a staff research physicist at PPPL. Parisi is the lead author of three articles describing the model that were published in the journals Nuclear Fusion and Physics of Plasma. The primary paper focuses on a part of the plasma called the pedestal, which is located at the edge. The pedestal is prone to instabilities because the plasma's temperature and pressure often drop sharply across this area.

Tokamak experiments provide unique data for validating spacecraft heat shield ablation models

When a spacecraft enters a thick atmosphere at a high velocity, it rapidly compresses the gas in front of it. This creates temperatures high enough to ionize the gas molecules into a hot, dense plasma. To protect against damage, spacecraft are typically covered by a heat shield material that burns in a controlled manner. This process is called ablation. Though current materials are effective for present-day missions, future missions require better heat shields.

To help develop them, scientists for the first time used a device known as a tokamak to study what happens to these materials in a hot plasma. In a series of experiments, the team exposed stationary graphite rods to the plasma near the floor of the tokamak. They then injected small carbon pellets deeper into the core of the plasma to observe how different carbon-based materials burn in conditions relevant to spacecraft entry into atmospheres.

Tokamaks are donut-shaped devices that can trap plasmas with strong magnetic fields. Scientists primarily use these devices for research into fusion energy. Conditions in a tokamak plasma can be similar to those experienced during some of the most challenging space missions ever attempted, such as the Galileo probe entry into Jupiter's atmosphere. Although the Galileo mission was successful, its heat shield occupied about half the mass of the probe. This left little capacity for scientific instruments.

Scientists at have conducted research showing that a powder dropper can successfully drop boron powder into high-temperature plasma within tokamaks that have parts made of a heat-resistant material known as tungsten.

What is the connection between boron, an element in a common household cleaner, and tokamaks, ring-shaped fusion facilities that heat fuel to million-degree temperatures? Scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have conducted research showing that a PPPL-developed powder dropper can successfully drop boron powder into high-temperature plasma within tokamaks that have parts made of a heat-resistant material known as tungsten. Scientists want to confirm they can use this process to apply boron to tungsten parts because bare tungsten walls can hurt plasma performance if the plasma damages the tungsten.

Because of its high melting point, tungsten is increasingly used in tokamaks to help components withstand the intense heat of the fusion process. Boron partly shields the tungsten from the plasma and prevents the tungsten from leaking into the plasma; it also absorbs any stray elements like oxygen that may be in the plasma from other sources. These unwanted impurities could cool the plasma and quench the fusion reactions.

"We need a way to deposit boron coatings without turning off the tokamaks' magnetic field, and that's what the powder dropper allows us to do," said Grant Bodner, a postdoctoral researcher at PPPL who was the lead author of the research paper reporting the results in Nuclear Fusion. The research was performed using the W Environment in Steady-State Tokamak (WEST), operated by France's Atomic Energy Commission (CEA). "WEST is one of the few full-tungsten environments that can help us test this technology at long pulses," Bodner said.

Innovative new magnet could facilitate development of fusion and medical devices

Scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have designed a new type of magnet that could aid devices ranging from doughnut-shaped fusion facilities known as tokamaks to medical machines that create detailed pictures of the human body.

Tokamaks rely on a central electromagnet known as a solenoid to create electrical currents and magnetic fields that confine the plasma—the hot, charged state of matter composed of free electrons and atomic nuclei—so fusion reactions can occur. But after being exposed over time to energetic subatomic particles known as neutrons emanating from the plasma, insulation surrounding the electromagnet's wires can degrade. If they do, the magnet could fail and reduce a tokamak's ability to harness fusion power.

In this new type of magnet, metal acts as insulation and therefore would not be damaged by particles. In addition, it would operate at higher temperatures than current superconducting electromagnets do, making it easier to maintain.

Scientists have used a mathematical technique to design powerful magnets with straighter shapes for stellarator fusion facilities, allowing for easier manufacturing and maintenance.

Harnessing the power that makes the sun and stars shine could be made easier by powerful magnets with straighter shapes than have been made before. Researchers linked to the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have found a way to create such magnets for fusion facilities known as stellarators.

Such facilities have complex twisted magnetic coils, compared with the straight up-and-down coils in more widely used tokamak facilities, and can produce fusion reactions without the risk of disruptions that tokamaks face. This advantage makes stellarators a candidate to serve as the model for a next-generation fusion pilot plant.

Now, by adding sections to the stellarator coils that are relatively straight, researchers could both reduce the manufacturing cost and make it easier to install openings that would allow technicians to repair the device's interior. Both innovations could aid the development of a stellarator power plant, replicating fusion on Earth for a virtually inexhaustible supply of power to generate electricity without producing greenhouse gases or long-lived radioactive waste.

Research confirms ingredient in household cleaner could improve fusion reactions

Want to improve your chances of making electricity from fusion? Look no further than the cleaners under your kitchen sink.

Research led by scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) provides new evidence that particles of boron, the main ingredient of Borax household cleaner, can coat internal components of doughnut-shaped plasma devices known as tokamaks and improve the efficiency of the fusion reactions.

"Our experiment brings key insights into how this technique works," said PPPL physicist Alessandro Bortolon, lead author of a paper reporting the findings in Nuclear Fusion. "The results will help clarify whether the controlled injection of boron powder could be used to support efficient operation of future fusion reactors."

Fusion combines light elements in the form of plasma—the hot, charged state of matter composed of free electrons and atomic nuclei—in a process that can generate massive amounts of energy. Scientists are seeking to harness fusion, which powers the sun and stars, to create a virtually inexhaustible supply of power to generate electricity.

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