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The challenge of extreme heat in fusion

In a fusion reactor temperatures in the plasma core reach millions of degrees. At the edge of the plasma this energy must be safely removed through a region known as the divertor. Conventional solid materials, such as tungsten, struggle under these conditions, suffering from erosion, cracking, or even melting.

To make fusion viable as a long-term energy source, new solutions are needed that can dissipate heat before it reaches solid surfaces, reducing damage and extending component lifetimes.

A vapour shield made of lithium

Romano鈥檚 research focuses on an alternative approach: using liquid lithium to create a protective vapour cloud. When exposed to the hot plasma, lithium evaporates and forms a dense vapour layer. Incoming plasma particles then lose energy through collisions and radiation within this cloud, significantly reducing the heat that reaches the underlying surface.

Experiments performed at the Magnum鈥慞SI linear plasma device demonstrate that this vapour shielding can substantially lower the heat flux at the target, redistributing energy to surrounding structures instead.

Keeping lithium in the right place

While lithium is highly effective near the divertor, it must not spread into the main fusion plasma, where it could disrupt reactor performance. Romano investigated how the vapour box geometry can confine lithium within the divertor region.

His results show that lithium confinement depends strongly on factors such as wall temperature, condensation processes, and plasma-driven transport. Carefully designed geometries and operating conditions can ensure that lithium remains largely contained while maintaining the protective vapour layer.

From controlled evaporation to self-regulating protection

The research also compared different ways of generating lithium vapour. When lithium is externally heated, the vapour production can be precisely controlled, but suffers from lag as it takes time to heat and cool. In contrast, when evaporation is driven directly by the plasma, the system becomes self-regulating: higher heat loads automatically produce more vapour, strengthening the shielding effect. This adaptive behavior is particularly attractive for future fusion reactors, where operating conditions can vary significantly over time.

Toward viable fusion power

Romano鈥檚 work provides experimental evidence that a lithium Vapour Box Divertor can both reduce heat loads and keep lithium confined, two essential requirements for practical fusion energy systems. While challenges remain in areas such as long-duration operation and temperature control, his findings mark an important step toward robust, heat-resistant divertor designs.

By combining plasma physics, materials science, and innovative engineering, this research contributes to making fusion energy a more realistic and sustainable power source for the future.