A diffusion pump divertor system for simultaneous vapor delivery, vacuum pumping, and heat exhaust in fusion devices

Background

The field of magnetic confinement fusion, exemplified by devices such as tokamaks and stellarators, is driven by the need to achieve and sustain the extreme conditions necessary for nuclear fusion reactions. One of the most critical engineering challenges in these reactors is the management of intense heat and particle fluxes emanating from the plasma, particularly in the divertor region where exhaust and impurities are handled. Maintaining ultra-high vacuum conditions is equally essential, as even trace contaminants or improper gas handling can degrade plasma performance, reduce fusion efficiency, and damage sensitive reactor components. As fusion reactors scale up in power and duration, the demands on heat exhaust and vacuum pumping systems intensify, necessitating innovative solutions that can operate continuously, efficiently, and compatibly with the reactor environment.

Current approaches to vapor delivery and vacuum pumping in fusion devices suffer from significant limitations. Traditional vapor delivery methods, such as evaporation, lack the precision to control both the spatial and quantitative aspects of vapor deposition, leading to uneven plasma conditioning and potential performance losses. Vacuum pumps commonly used in fusion, including cryo-pumps and turbo-pumps, present operational drawbacks: cryo-pumps require frequent regeneration cycles, interrupting continuous operation, while turbo-pumps are vulnerable to failure in strong magnetic fields and may be incompatible with tritium, a key fusion fuel. Mercury-based diffusion pumps, though effective in some vacuum applications, pose an unacceptable contamination risk to the plasma. These limitations hinder the ability to manage heat and particle exhaust effectively, restrict operational flexibility, and complicate reactor maintenance, underscoring the need for more integrated and robust solutions.

Technology

This technology is an integrated diffusion pump divertor system designed specifically for fusion devices such as tokamaks and stellarators. It features the direct incorporation of a diffusion pump into the divertor section, where nozzles emit high-speed, often supersonic, vapor jets—typically composed of lithium vapor. These jets serve multiple roles: they precisely deliver controlled amounts of vapor into the divertor region, entrain and direct gas molecules and contaminants toward an exhaust, and absorb significant heat flux from the plasma. The system is engineered to condense the vapor for removal as liquid or exhaust it as gas, and it can be constructed using conventional materials and manufacturing techniques compatible with the demanding plasma and vacuum environments of fusion reactors. The use of lithium vapor not only aids in heat removal and vacuum pumping but also contributes to tritium breeding, which is vital for sustaining fusion reactions.

What differentiates this solution is its multifunctional approach to several core challenges in fusion reactor operation. Unlike traditional vapor delivery and vacuum pumping methods—such as cryo-pumps, which require downtime for regeneration, or turbo-pumps, which struggle in strong magnetic fields—this system provides continuous, intrinsic vacuum pumping while simultaneously managing extreme heat loads and plasma-facing component protection. The supersonic vapor jets enable precise, localized vapor delivery and efficient removal of neutral particles and contaminants, significantly enhancing volumetric pumping rates compared to existing technologies. Furthermore, the system’s adaptability allows for effective impurity control and compatibility with tritium breeding, all while minimizing plasma contamination and supporting continuous operation. This integrated, high-performance approach leverages established diffusion pump principles in a novel configuration, offering a scalable and robust solution for next-generation fusion devices.

Benefits

• Precise control of vapor delivery improves plasma conditioning and heat flux management.
• Supersonic vapor jets provide intrinsic vacuum pumping by entraining and removing gases and contaminants.
• Efficient heat exhaust through vapor jets protects plasma-facing components and enables working fluid recycling.
• Lithium vapor use supports tritium breeding, a key fuel component for fusion reactors.
• Continuous operation without downtime, unlike cryo-pumps requiring regeneration.
• Reduced plasma contamination due to controlled vapor flow and limited backflow.
• Compatibility with conventional materials and manufacturing facilitates integration and scalability.

Applications

• Fusion reactor heat exhaust management
• Vacuum pumping for fusion devices
• Plasma impurity and contaminant removal
• Tritium breeding in fusion reactors
• Continuous operation fusion divertor systems

Additional info

This system integrates a diffusion pump into a fusion device’s divertor. It uses nozzles to emit high-speed vapor jets, typically lithium, for dual technical functions: precisely delivering vapor and facilitating vacuum pumping by entraining gas molecules. The jets also absorb plasma heat flux, enabling heat exhaust, working fluid recycling, and potential tritium breeding.