topic Research

ITER

With JET (Joint European Torus; location: Culham, UK), it has been possible to get very close to the ignition conditions of a burning, i.e. self-maintaining fusion plasma. There is therefore worldwide agreement that the next step must be an experiment which generates considerably more fusion power than is necessary for heating the plasma. JET achieved a fusion power of 16 MW for 2 s, while 65% of the used energy was recovered.

ITER is mainly to contribute to achieving and optimizing a self-maintaining fusion reaction, to studying the fuel cycle, materials and systems as well as to gathering experience with the transport of helium cores (arising from the melting of deuterium and tritium as "ashes").

After the end of the cold war, ITER was initiated jointly by the presidents Gorbachev and Reagan. The US, Russia, Japan and the European Union participated in the first design phase from 1992 to1998. In 1998, the US withdrew from the cooperation. After a phase of reconstruction, which led to a considerable reduction of costs, international negotiations on the construction of ITER were taken up in 2001 on the basis of documentation allowing decisions to be made.

Like its predecessor JET (the currently largest fusion experiment worldwide), ITER will be a so-called Tokamak; this is the best studied development line of fusion reactors to date. Tokamaks have a ring-shaped ("toroidal") plasma. The magnetic field which is necessary for the inclusion of the plasma is generated by superconducting coils encompassing the ring (cf. picture: Tokamak - Schematic View). However, a magnetic field created in this way is weaker on the outside than on the inside; without corrections the plasma would therefore drift to the outside. Poloidal field coils are used for correction. An increasing electric current in the poloidal field coils generates a secondary current in the plasma, similar to a transformer; this secondary magnetic field completes the inclusion of the plasma. However, the current in the poloidal field coil cannot take any intensity and therefore cannot increase indefinitely. Tokamak plasmas are therefore pulsed by nature, i.e. discontinuous. The pulse lengths envisaged for ITER will be of some minutes up to one hour.

ITER has become a global project by now with the participation of many large industrialized nations: the European Union, Japan, Russia, since 2003 (once again) the US, as well as China and South Korea.