Scientists at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have made groundbreaking advancements in nuclear fusion technology, overcoming significant heat management challenges inside fusion reactors. Central to their work is the development of a lithium vapor “cave” and a porous plasma-facing wall, both designed to protect the tokamak, a doughnut-shaped fusion vessel, from the intense heat produced by plasma.
Led by Rajesh Maingi, head of tokamak experimental science at PPPL, the team has extensively studied the use of liquid lithium to enhance fusion performance. Their recent paper in Nuclear Fusion outlines the optimal placement of the lithium vapor cave near the tokamak’s center stack, which allows it to dissipate excess heat from the private flux region, a distinct area from the core plasma, without affecting the plasma’s temperature. The lithium vapor cave acts as a crucial barrier, capturing heat before it reaches the vessel’s walls.
Initially, the design for the lithium vapor containment resembled a full metal box, but the team discovered that a simpler, half-box configuration could effectively control heat without unnecessary complexity. This breakthrough not only optimizes the heat absorption capabilities of the evaporating lithium but also makes the construction of the device more cost-effective and practical.
In addition to the lithium vapor cave, PPPL scientists have proposed an alternative heat management method: a porous, plasma-facing wall that allows liquid lithium to flow directly onto the surface, cooling specific hot zones. This design innovation eliminates the need for structural changes to the confinement vessel, simplifying maintenance.
These innovations are significant strides toward the goal of commercial fusion energy, offering promising solutions to the critical challenge of heat management in fusion reactors and bringing us closer to sustainable and abundant energy sources.