Unlike tokamaks, which are simpler and have historically led in fusion research, stellarators employ complex magnetic fields to confine plasma within a donut-shaped chamber. W7-X's record places it ahead in the race for steady-state fusion, despite its smaller size compared to larger devices like JET and JT60U. This achievement confirms that stellarators can approach the performance levels necessary for continuous energy production.
"This record is a tremendous achievement by the international team," said Prof. Dr. Thomas Klinger, Head of Operations at W7-X. "Elevating the triple product to tokamak levels during long plasma pulses marks another important milestone on the way toward a power-plant-capable stellarator."
A key to this success was the introduction of a novel pellet injector developed by Oak Ridge National Laboratory (ORNL) in the United States. This system fires frozen hydrogen pellets into the plasma at high speed, enabling continuous refueling and supporting long plasma durations. During the record-setting experiment, 90 hydrogen pellets were injected over 43 seconds, while powerful microwaves simultaneously heated the plasma to temperatures exceeding 20 million degrees Celsius, peaking at 30 million.
The triple product was determined using a combination of diagnostics from Princeton Plasma Physics Laboratory's X-ray spectrometer, IPP's unique interferometer for electron density measurements, and IPP-developed tools for energy confinement time. Additional contributors included CIEMAT, which provided simulation data, and HUN-REN Centre for Energy Research, which supplied fast-camera observations.
Beyond the triple product record, the OP 2.3 campaign achieved an energy turnover of 1.8 gigajoules during a 360-second discharge and plasma pressure relative to magnetic pressure reaching 3% - a key parameter for future reactors. Prof. Dr. Robert Wolf of IPP emphasized that these results represent critical steps in validating the stellarator concept through strong international collaboration.
The triple product - a key metric known as the Lawson criterion - measures plasma density, temperature, and energy confinement time. For a self-sustaining fusion reaction, this product must exceed a defined threshold, marking the point at which a reactor can produce more power than it consumes.
Since September 2024, ORNL's continuously operating pellet injector has played a crucial role in these achievements. The device forms a strand of frozen hydrogen, cuts it into millimeter-sized pellets, and injects them into the plasma at speeds of up to 800 meters per second, ensuring a steady supply of fuel essential for fusion power plants.
Wendelstein 7-X's latest results bring the dream of clean and abundant fusion energy a step closer to reality.
Research Report:Wendelstein 7-X sets new performance records in nuclear fusion research
Related Links
Max-Planck-Institut fur Plasmaphysik
Powering The World in the 21st Century at Energy-Daily.com
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