Chamber technology concepts for inertial fusion energy—three recent examples

The most serious challenges in the design of chambers for inertial fusion energy (IFE) are: (1) protecting the first wall from fusion energy pulses on the order of several hundred megajoules released in the form of X-rays, target debris, and high energy neutrons; and (2) operating the chamber at a pulse repetition rate of 5–10 Hz (i.e. re-establishing the wall protection and chamber conditions needed for beam propagation to the target between pulses). In meeting these challenges, designers have capitalized on the ability to separate the fusion burn physics from the geometry and environment of the fusion chamber. Most recent conceptual designs use gases or flowing liquids inside the chamber. Thin liquid layers of molten salt or metal and low pressure, high-Z gases can protect the first wall from X-rays and target debris, while thick liquid layers have the added benefit of protecting structures from fusion neutrons thereby significantly reducing the radiation damage and activation. The use of thick liquid walls is predicted to: (1) reduce the cost of electricity by avoiding the cost and down time of changing damaged structures; and (2) reduce the cost of development by avoiding the cost of developing a new, low-activation material. Various schemes have been proposed to assure chamber clearing and renewal of the protective features at the required pulse rate. Representative chamber concepts are described, and key technical feasibility issues are identified for each class of chamber. Experimental activities (past, current and proposed) to address these issues and technology research and development needs are discussed.