☢️Nuclear Fusion Technology Unit 11 – Current Fusion Research Facilities

Key Fusion Research Goals

• Achieve sustained, controlled fusion reactions that produce more energy than required to initiate and maintain the reaction
• Develop fusion reactors capable of generating electricity at a commercial scale, providing a virtually inexhaustible, clean, and safe energy source
• Optimize plasma confinement and stability to maintain high-temperature, high-density plasmas for extended periods
• Investigate and mitigate plasma instabilities, such as disruptions and edge localized modes (ELMs), which can damage reactor components
• Develop materials that can withstand the extreme heat and neutron flux within a fusion reactor, ensuring long-term structural integrity
• Minimize the production of radioactive waste by using low-activation materials and designing for efficient tritium breeding and extraction
• Advance the understanding of plasma physics, including turbulence, transport, and interactions with electromagnetic fields
• Collaborate internationally to share knowledge, resources, and expertise in fusion research and development

Major Fusion Facility Types

• Magnetic confinement devices use strong magnetic fields to confine and control high-temperature plasmas, preventing them from touching the reactor walls
  • Tokamaks are the most widely studied magnetic confinement devices, featuring a toroidal (doughnut-shaped) chamber with helical magnetic field lines
  • Stellarators employ complex, non-axisymmetric magnetic field configurations to confine plasmas, offering potential advantages in steady-state operation and stability
• Inertial confinement facilities use high-power lasers or particle beams to compress and heat small fuel pellets, initiating fusion reactions
  • Laser-driven inertial confinement devices, such as the National Ignition Facility (NIF) in the United States, focus multiple high-energy laser beams onto a target pellet
  • Z-pinch devices, like the Z Machine at Sandia National Laboratories, use strong electrical currents to compress and heat fuel
• Hybrid devices combine elements of magnetic and inertial confinement, such as magnetized target fusion or magneto-inertial fusion
• Alternate concepts explore novel approaches to fusion, including dense plasma focus, colliding beam fusion, and muon-catalyzed fusion

Tokamak Experiments

• ITER (International Thermonuclear Experimental Reactor) is a large-scale international collaboration aiming to demonstrate the scientific and technological feasibility of fusion energy
  • Located in France, ITER will be the world's largest tokamak, with a plasma volume of 840 cubic meters
  • Designed to produce 500 MW of fusion power for 400-600 seconds, achieving a Q value (ratio of fusion power output to input power) of 10 or more
• JET (Joint European Torus) is currently the world's largest operational tokamak, located in the United Kingdom
  • Holds the record for the highest fusion power output achieved in a tokamak: 16 MW in 1997
  • Serves as a test bed for ITER technologies and operational scenarios
• KSTAR (Korea Superconducting Tokamak Advanced Research) is a superconducting tokamak in South Korea, focusing on steady-state operation and advanced plasma control
• EAST (Experimental Advanced Superconducting Tokamak) is a Chinese superconducting tokamak that has achieved long-pulse, high-performance plasma operations
• JT-60SA (Japan Torus-60 Super Advanced) is a superconducting tokamak in Japan, designed to support ITER and study advanced plasma scenarios

Stellarator Projects

• Wendelstein 7-X is the world's largest stellarator, located in Germany
  • Aims to demonstrate the feasibility of stellarators as a viable fusion reactor concept
  • Features a complex, optimized magnetic field configuration to minimize plasma instabilities and improve confinement
• Large Helical Device (LHD) is a superconducting stellarator in Japan, studying high-performance plasma confinement and steady-state operation
• Helically Symmetric Experiment (HSX) is a stellarator at the University of Wisconsin-Madison, designed to test the concept of quasi-helical symmetry for improved confinement
• National Compact Stellarator Experiment (NCSX) was a proposed stellarator project in the United States, aimed at studying compact, high-beta stellarator configurations

Inertial Confinement Facilities

• National Ignition Facility (NIF) is the world's largest and most energetic laser facility, located at Lawrence Livermore National Laboratory in the United States
  • Focuses 192 high-power laser beams onto a small target filled with deuterium-tritium fuel
  • Aims to achieve fusion ignition and gain, where the energy released from fusion reactions exceeds the energy delivered by the lasers
• Laser Mégajoule (LMJ) is a large-scale laser facility in France, similar in design to the NIF
  • Designed for both fusion research and nuclear weapons stewardship
• OMEGA Laser Facility at the University of Rochester in the United States is a 60-beam laser system used for inertial confinement fusion research and high-energy-density physics experiments
• Z Machine at Sandia National Laboratories in the United States is the world's most powerful X-ray generator, used for Z-pinch inertial confinement fusion research and materials science studies

Alternative Fusion Concepts

• Magnetized target fusion devices combine elements of magnetic and inertial confinement
  • Examples include General Fusion's acoustically-driven magnetized target fusion reactor and Los Alamos National Laboratory's Plasma Liner Experiment (PLX)
• Field-reversed configuration (FRC) devices confine high-beta plasmas in a compact, self-organized magnetic field geometry
  • TAE Technologies' C-2W device is the world's largest FRC experiment, aiming to demonstrate net energy production
• Spheromaks are compact magnetic confinement devices with a self-organized, toroidal magnetic field structure
  • The Sustained Spheromak Physics Experiment (SSPX) at Lawrence Livermore National Laboratory studied the formation and confinement of spheromak plasmas
• Dense plasma focus devices use pulsed high-current discharges to create and compress high-density plasmas
  • The Dense Plasma Focus (DPF) device at Lawrenceville Plasma Physics is investigating the use of DPF for fusion power generation

Diagnostic Tools and Technologies

• Magnetic diagnostics measure the magnetic field structure and plasma current in fusion devices
  • Examples include Rogowski coils, Hall probes, and diamagnetic loops
• Optical diagnostics use visible, infrared, and ultraviolet light to study plasma properties and behavior
  • Thomson scattering measures electron temperature and density by analyzing laser light scattered by plasma electrons
  • Spectroscopy analyzes the wavelengths of light emitted or absorbed by plasma ions to determine ion temperature, density, and flow velocity
• Particle diagnostics detect and analyze the particles produced by fusion reactions, such as neutrons and charged particles
  • Neutron detectors, like fission chambers and scintillators, measure the neutron flux and energy spectrum
  • Charged particle detectors, such as Faraday cups and silicon surface barrier detectors, measure the energy and flux of ions and electrons
• Microwave and millimeter-wave diagnostics probe the plasma using high-frequency electromagnetic waves
  • Reflectometry measures the plasma density profile by analyzing the reflection of microwave signals from the plasma
  • Electron cyclotron emission (ECE) diagnostics measure the electron temperature profile by detecting the cyclotron radiation emitted by electrons in the plasma

Challenges and Future Directions

• Developing materials that can withstand the extreme heat and neutron flux in a fusion reactor is a critical challenge
  • Tungsten and other refractory metals are being investigated for use in plasma-facing components
  • Low-activation steels and advanced composites are being developed for structural components
• Tritium breeding and extraction technologies are essential for the self-sustaining operation of fusion reactors
  • Lithium-containing blankets surrounding the reactor chamber can breed tritium through interactions with fusion neutrons
  • Efficient methods for extracting and purifying tritium from the blanket are being developed
• Superconducting magnets are necessary for the efficient operation of magnetic confinement devices
  • High-temperature superconductors, such as REBCO (rare-earth barium copper oxide) tapes, offer the potential for higher magnetic field strengths and improved plasma confinement
• Advanced plasma heating and current drive methods are being developed to optimize fusion performance
  • Neutral beam injection (NBI) systems accelerate high-energy neutral particles into the plasma for heating and current drive
  • Radio-frequency (RF) heating methods, such as electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH), use high-frequency electromagnetic waves to heat the plasma
• Integrated modeling and simulation tools are essential for understanding and predicting fusion plasma behavior
  • High-performance computing platforms enable the development of complex, multi-scale models that couple plasma physics, materials science, and engineering aspects of fusion systems
• Continued international collaboration and support for fusion research are crucial for advancing the field and realizing the potential of fusion as a sustainable energy source