Material Insights · Understanding the Material World

Fusion reactors: Techniques

Doughnuts, twisted coils and 192 laser beams compared

What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.

Three machine families lead: tokamaks and stellarators, which hold hot plasma in magnetic fields, and laser inertial confinement, which crushes tiny fuel capsules. All are at the research stage and none supplies grid power.

Comparison

MethodEfficiencyCostLife-cycle emissionsMaturityScale
Tokamaks (ITER, JET, WEST, SPARC)34568910111721Q of 0.33 for 5 seconds at JET (2021); ITER's design target is Q=10 in 400-second pulses. WEST held a plasma for 1,337 seconds in 2025.ITER's 2024 rebaseline adds about EUR 5 billion. Early commercial plants modelled above USD 150/MWh; about USD 80-100/MWh (2020 prices) needed to compete after 2040. MIT scenarios assume USD 5,600-8,000/kW in 2050 (2021 dollars).About 9 g CO2e/kWh in a 2001 design study (15 for fission and wind in the same study); no newer quantitative life-cycle study was found.research No grid electricity. JET record 69 MJ in 5 seconds (2023). ITER deuterium-tritium operation planned from 2039. CFS installed the first of 18 SPARC magnets in January 2026 and aims to switch SPARC on in 2027.
Stellarators (Wendelstein 7-X)7No deuterium-tritium operation, so no Q. W7-X sustained a record triple product (the density-temperature-confinement measure of closeness to ignition) for 43 seconds in 2025.No published plant cost.No life-cycle study found.research Experimental devices only.
Laser inertial confinement (NIF)121519Target gain 4.13 (April 2025); wall-plug about 3% (calculated) because the 1980s-era laser draws about 300 MJ per shot.No published plant cost; pilot plants are concepts.No life-cycle study found.research Single shots, a few per day; 11 of 53 surveyed private firms pursue inertial approaches.

None of the routes has a cost or emissions record, because none has produced net electricity. Magnetic confinement has the larger industry (25 of 53 surveyed firms) and the clearest engineering path, though ITER's deuterium-tritium start has slipped four years to 2039. Lasers have achieved the only ignition but face the widest wall-plug gap.

How each method works

Tokamaks (ITER, JET, WEST, SPARC)

A doughnut-shaped vessel holds deuterium-tritium plasma above 100 million degrees C, kept off the walls by magnets and a current in the plasma. Fusion neutrons heat a surrounding blanket, which would drive a turbine.34568910111721

Stellarators (Wendelstein 7-X)

Twisted external coils, rather than a plasma current, create the confining field. This avoids sudden current disruptions and suits steady operation, at the price of complex coils.7

Laser inertial confinement (NIF)

192 laser beams heat a small gold cylinder, whose X-rays implode a pea-sized capsule of frozen deuterium-tritium for billionths of a second. A plant would need about 10 shots a second with mass-produced targets.121519

Sources

  1. National Ignition Facility (FY2025 annual report) Lawrence Livermore National Laboratory, 2025
  2. Ignition Accomplished: NIF Looks to the Future Optica, Optics & Photonics News, 2022
  3. What will ITER do? ITER Organization, 2025
  4. Baseline press conference summary, July 2024 ITER Organization, 2024
  5. Nuclear-fusion reactor smashes energy record Nature, 2022
  6. JET's final tritium experiments yield new fusion energy record UK Government (DESNZ / UKAEA), 2024
  7. Wendelstein 7-X sets new performance records in fusion research Max Planck Institute for Plasma Physics, 2025
  8. World record for WEST DIFFER, 2025
  9. Can fusion energy be cost-competitive and commercially viable? An analysis of magnetically confined reactors (Lindley et al., Energy Policy 177) Elsevier, 2023
  10. The Role of Fusion in a Decarbonized Electricity System: Summary of Findings MIT Energy Initiative, 2024
  11. The Potential for Fusion Power to Mitigate U.S. Greenhouse Gas Emissions (Meier and Kulcinski, Fusion Science and Technology 39) American Nuclear Society, 2001
  12. The global fusion industry in 2025 Fusion Industry Association, 2025
  13. ITER fusion reactor hit by massive decade-long delay and EUR 5bn price hike Physics World, 2024
  14. SLAC scientists explain what is inertial fusion energy SLAC National Accelerator Laboratory via Newswise, 2023
  15. Commonwealth Fusion Systems installs reactor magnet, lands deal with Nvidia TechCrunch, 2026