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Scientists discover a process that stabilizes fusion plasmas



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IMAGE: These are the physicists Allan Reiman, left, and Nat Fish.
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Credit: Elle Starkman / PPPL Communications Department

Scientists who want to bring the sun's and stars' fusion reaction to Earth need to keep the Superhot plasma free from interference. Researchers at the US Department of Energy's (DOEs) Princeton Plasma Physics Laboratory (PPPL) have now discovered a process that can help control the most dangerous disorders.

Replication of Merges that Unlimited Energy Merges by Merging Atomic Nuclei The state of matter, known as plasma, could produce clean and virtually unlimited electricity for power generation for cities and industries everywhere. The detection and control of fusion energy is therefore a key scientific and technical challenge for researchers around the world.

Magnetic Island Generation

The PPPL finding published in Physical Review Letters focuses on the so-called tearing modes ̵

1; plasma instabilities that form magnetic islands, a major cause of plasma disruption. These islands, bubble-like structures that form in the plasma, can grow and cause disturbing events that disrupt fusion reactions and damage donut-shaped devices called "tokamaks" that harbor the reactions.

In the 1980s, researchers found that the use of radio frequency (RF) waves to drive the plasma current could stabilize the disruption modes and reduce the risk of interference. However, researchers have not noticed that small changes – or disturbances – in the temperature of the plasma can improve the stabilization process as soon as an important performance threshold is exceeded. The physical mechanism PPPL has identified works as follows:

  • Temperature disturbances affect the strength of the current drive and the amount of RF power deposited in the islands.
  • The perturbations and their effects on the deposition of power feedback against each other in a complex or nonlinear way.
  • When the feedback combines with the sensitivity of the current drive to temperature disturbances, the efficiency of the stabilization process increases.
  • In addition, improved stabilization is less likely to be affected by misaligned power drives that do not hit the center of the island.

The overall effect of this process produces what is termed "RF current condensation." Concentration of RF power within the island that prevents growth. "The power buildup is greatly increased," said Allan Reiman, theoretical physicist at the PPPL and lead author of the newspaper. "If the current deposition on the island exceeds a threshold, there is a temperature jump that greatly enhances the stabilization effect, which allows for the stabilization of larger islands than previously thought."

Beneficial to ITER

This method may be particularly useful for ITER, the International Tokamak under construction in France, to demonstrate the feasibility of fusion energy. "There is a concern that islands are getting big and ITER is disrupting," said Reiman. "Taken together, these new effects should facilitate the stabilization of ITER plasmas."

Reiman worked with Professor Nat Fisch, Deputy Director of Academic Affairs at the PPPL and co-author of the report. Fisch had shown in a seminal 1970s paper that RF waves could be used to induce currents to limit tokamak plasmas through a process now called "RF power drive." These RF currents could also stabilize the tear modes. The use of rf current drive to stabilize rupture modes may have been even more important to the tokamak program than the use of these plasma confining flows, "said Fisch.

said," Reiman's paper from 1983 essentially launched experimental campaigns Tokamaks worldwide to stabilize the tear modes. "He also added," In addition to predicting the stabilization of rupture modes by RF, the 1983 article also highlighted the importance of temperature dysfunction in magnetic islands. "

Underrated Feature

The new article takes a fresh look at the effects of these temperature dysfunctions on the islands, a trait that has been undervalued since the publication of the 1983 paper. "We have basically gone back 35 years to take that idea a little further by: we explored the fascinating physics and the bigger impact of positive feedback n, "said Fisch. "It turns out these implications could be very important to today's tokamak program."

Theorists began their recent work with a simple model and moved on to more complex ones to tackle the key issues. You are now planning to create an even more detailed image with even more sophisticated models. They are also working to propose experimental campaigns that highlight these new effects. Support for this research comes from the DOE Office of Science.

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PPPL, located on the Forrestal campus of Princeton University in Plainsboro, New Jersey, is dedicated to creating new knowledge about the physics of plasmas – ultra-hot, charged gases – and practical manufacturing solutions of fusion energy. Managed by the University of the US Department of Energy's Office of Science, which is the largest supporter of basic science research in the United States, the lab is working to address some of the most urgent challenges of our time. For more information, see science.energy.gov.

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