An Overview of the Magnetic Fusion Landscape and Key Technical Hurdles to Overcome

AN OVERVIEW OF THE MAGNETIC FUSION LANDSCAPE AND KEY TECHNICAL HURDLES TO OVERCOME

Prof. Dennis Whyte

Director, Plasma Science & Fusion Center

Hitachi America Professor of Engineering, Nuclear Science & Engineering

Massachusetts Institute of Technology

Magnetic confinement is a leading candidate to produce the necessary conditions for creating net fusion energy. Recent scientific and technical advances have improved the prospects for magnetic fusion and have also clarified the remaining challenges to realizing practical, economic fusion energy systems. An introduction to the basics of magnetic confinement will be followed by discussion of the significance of several recent advances, including record fusion energy production and duration in tokamaks, the optimization of transport losses in stellarators, and the development of high-field REBCO superconductor magnets that will impact all forms of magnetic fusion. The remaining hurdles to be reviewed include obtaining plasma energy gain in the SPARC and ITER devices, and the required parallel technology development in robust first walls, heat removal and tritium production.

This presentation followed the Annual General Meeting held on September 28, 2022.

Recording of the full presentation available soon.

National Ignition Facility experiment puts researchers at threshold of fusion ignition

On Aug. 8, 2021, an experiment at Lawrence Livermore National Laboratory’s (LLNL’s) National Ignition Facility (NIF) made a significant step toward ignition, achieving a yield of more than 1.3 megajoules (MJ). This advancement puts researchers at the threshold of fusion ignition, an important goal of the NIF, and opens access to a new experimental regime.

The experiment was enabled by focusing laser light from NIF —the size of three football fields — onto a target the size of a BB that produces a hot-spot the diameter of a human hair, generating more than 10 quadrillion watts of fusion power for 100 trillionths of a second.

“These extraordinary results from NIF advance the science that NNSA depends on to modernize our nuclear weapons and production as well as open new avenues of research,” said Jill Hruby, DOE under secretary for Nuclear Security and NNSA administrator.

The central mission of NIF is to provide experimental insight and data for NNSA’s science-based Stockpile Stewardship Program. Experiments in pursuit of fusion ignition are an important part of this effort. They provide data in an important experimental regime that is extremely difficult to access, furthering our understanding of the fundamental processes of fusion ignition and burn and enhancing our simulation tools to support stockpile stewardship. Fusion ignition is also an important gateway to enable access to high fusion yields in the future.

“This result is a historic step forward for inertial confinement fusion research, opening a fundamentally new regime for exploration and the advancement of our critical national security missions. It is also a testament to the innovation, ingenuity, commitment and grit of this team and the many researchers in this field over the decades who have steadfastly pursued this goal,” said LLNL Director Kim Budil. “For me it demonstrates one of the most important roles of the national labs – our relentless commitment to tackling the biggest and most important scientific grand challenges and finding solutions where others might be dissuaded by the obstacles.”

While a full scientific interpretation of these results will occur through the peer-reviewed journal/conference process, initial analysis shows an 8X improvement over experiments conducted in spring 2021 and a 25X increase over NIF’s 2018 record yield.

“Gaining experimental access to thermonuclear burn in the laboratory is the culmination of decades of scientific and technological work stretching across nearly 50 years,” said Los Alamos National Laboratory Director Thomas Mason. “This enables experiments that will check theory and simulation in the high energy density regime more rigorously than ever possible before and will enable fundamental achievements in applied science and engineering.”

The experiment built on several advances gained from insights developed over the last several years by the NIF team including new diagnostics; target fabrication improvements in the hohlraum, capsule shell and fill tube; improved laser precision; and design changes to increase the energy coupled to the implosion and the compression of the implosion.

“This significant advance was only made possible by the sustained support, dedication and hard work of a very large team over many decades, including those who have supported the effort at LLNL, industry and academic partners and our collaborators at Los Alamos National Laboratory and Sandia National Laboratories, the University of Rochester’s Laboratory for Laser Energetics and General Atomics,” said Mark Herrmann, LLNL’s deputy program director for Fundamental Weapons Physics. “This result builds on the work and successes of the entire team, including the people who pursued inertial confinement fusion from the earliest days of our Laboratory. They should also share in the excitement of this success.”

Looking ahead, access to this new experimental regime will inspire new avenues for research and provide the opportunity to benchmark modeling used to understand the proximity to ignition. Plans for repeat experiments are well underway, although it will take several months for them to be executed.

Reference:  https://t.co/WhPL3Vt26e

WHAT IS FUSION?

Fusion is the energy source of the Sun and stars. In the tremendous heat and gravity at the core of these stellar bodies, hydrogen nuclei collide, fuse into heavier helium atoms and release tremendous amounts of energy in the process.

Twentieth-century fusion science identified the most efficient fusion reaction in the laboratory setting to be the reaction between two hydrogen isotopes, deuterium (D) and tritium (T). The DT fusion reaction produces the highest energy gain at the “lowest” temperatures.

Three conditions must be fulfilled to achieve fusion in a laboratory: very high temperature (on the order of 150,000,000° Celsius); sufficient plasma particle density (to increase the likelihood that collisions do occur); and sufficient confinement time (to hold the plasma, which has a propensity to expand, within a defined volume).

At extreme temperatures, electrons are separated from nuclei and a gas becomes a plasma—often referred to as the fourth state of matter. Fusion plasmas provide the environment in which light elements can fuse and yield energy.

– ITER Organization

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