Germany's Wendelstein 7-X (W7-X) stellarator has demonstrated sustained plasma confinement for 30 minutes, a new record for the device and a critical validation of its optimized magnetic field design. This extended pulse duration, achieved in late 2023, significantly surpasses previous records and moves W7-X closer to its goal of demonstrating the steady-state potential of stellarator-based fusion power. The experiment focused on maintaining plasma stability and controlling heat and particle exhaust under steady-state conditions, key challenges for future fusion power plants.

The W7-X stellarator, located at the Max Planck Institute for Plasma Physics in Greifswald, employs a complex, non-axisymmetric magnetic field coil system to confine the plasma. This design aims to overcome inherent plasma instabilities that plague traditional tokamak devices, potentially enabling continuous operation without the need for pulsed magnetic field reversals. The 30-minute plasma pulse utilized a hydrogen-helium fuel mix, operating at temperatures up to 6 keV and achieving a line-averaged electron density of 0.3 x 10^20 m^-3. The experiment's success is attributed to advancements in plasma control systems and improved divertor performance, which manage the intense heat flux from the plasma edge.

The W7-X stellarator, located at the Max Planck Institute for Plasma Physics in Greifswald, employs a complex, non-axisymmetric magnetic field coil system to confine the plasma.

This latest achievement builds upon W7-X's ongoing research program, which has progressively increased plasma performance since its first plasma in 2015. Previous milestones included achieving high plasma temperatures and demonstrating the effectiveness of the optimized magnetic field in reducing neoclassical transport losses. The ability to sustain plasma for extended periods is crucial for assessing the long-term material integrity of reactor components and for developing efficient energy extraction systems. The data gathered from these long pulses will inform the design of future stellarator power plants, such as the planned successor project, W7-X-II.

The stellarator approach, while technologically complex, offers a compelling alternative to tokamaks for achieving continuous fusion power. Unlike tokamaks, which require periodic current drive pulses that can introduce instabilities, stellarators theoretically offer inherent steady-state operation. However, the intricate three-dimensional magnetic field coils present significant engineering and manufacturing challenges. W7-X's success in achieving long-duration plasma pulses provides strong experimental evidence that these challenges are surmountable and that the stellarator concept is a viable path toward fusion energy.

Future experiments on W7-X will focus on further increasing plasma density and temperature, as well as investigating the behavior of fusion-relevant isotopes like deuterium. The insights gained will be invaluable for the broader fusion research community, particularly for projects aiming to demonstrate net energy gain and commercial viability. The sustained operation of W7-X is a critical step in de-risking the stellarator pathway and bolstering confidence in its potential to contribute to a future fusion energy landscape Source: IEEE Spectrum.