What is the status of fusion research? What physical and technological problems have still to be solved?

With the international ITER experimental reactor fusion research is to proceed to demonstration of an energy-yielding plasma. If successful, ITER will open the door to a fusion power plant. Present planning supposes that ITER will be followed up with a demonstration power plant supplying the grid with power. It is to prove that fusion energy can be reliably produced. This device, called DEMO, would no longer be an experimental device, but a power plant optimised to a single point of operation. This calls for a fundamental physical understanding of the system so that its properties can be calculated beforehand in detail.

Clarifying the physical principles of a fusion power plant will therefore continue to be an important objective and will occupy theoretical and experimental plasma physicists for some time yet. This will be paralleled by further development of the special technologies needed for a power plant, e.g. for plasma heating and for the blanket.

Physical and technological requirements here need to be reconciled. On the physics side, this is long-time operation in the Advanced Tokamak or Stellarator with stable, thermally well-insulated high-density plasmas with moderate wall loading.

On the technology side, this means energy-efficient heating of the plasma, current drive and further development of robust low-activation materials and energy-efficient blankets for taking up fusion energy at as high wall temperatures as possible.