Nuclear fusion happens incessantly within stars in the universe. It is the source of the energy of the sun, constituting the origin of all life on earth. Fusion energy is released when light atomic nuclei, in particular hydrogen and its isotopes, merge to form heavier nuclei in a hot environment such as stellar interiors. For fusion reactors on earth, the reaction of the hydrogen isotopes deuterium and tritium is favoured because of its large cross section. Deuterium (D) is contained in water, and tritium (T) can be obtained from lithium which is abundant in earth. This fusion reaction releases an α-particle, a neutron, and 17.6 MeV of energy. It takes place when heating the DT fuel to ignition temperatures of about 100 million degrees. The main challenge is to keep matter together at these high temperatures for a period long enough to achieve sufficient burn. In stars, gravity ensures confinement. For terrestrial fusion, magnetic and inertial confinement (MCF and ICF) are being pursued. MCF draws on magnetic fields to confine the fusion plasma and constitutes the basic concept underlying the multi-national enterprise ITER. Our sister institute, the Max Planck Institute for Plasma Physics (IPP) plays a central role in this effort. In ICF, on the other hand, confinement is achieved by mass inertia. In this case fusion burn has to occur within the short time the fuel keeps together by mass inertia. This is a fraction of a nanosecond. To speed up the fusion reactions, ICF therefore requires extremely high fuel density (more than thousand times solid density). The ICF scheme for spherical compression of small capsules is illustrated in the box.

High-power lasers are superior tools for fuel compression and ignition, because they can concentrate energy in space and time to an unparalleled extent. Two large-scale facilities producing laser pulses with million-joule energy, NIF at Livermore, USA, and MEGAJOULE at Bordeaux, France, are now under construction for laser-induced fusion. They are expected to actually achieve ignition and burn of DT fuel. Both experiments use the so-called indirect-drive approach.

Supported by the EURATOM (keep-in-touch activities) programme of the European Union, MPQ has been pursuing laser fusion research for more than 30 years, resulting in many important findings in the areas of laser absorption and laser-driven hydrodynamics (1975-85), as well as laser-driven radiation hydrodynamics (1985-95), which helped to enact declassification of indirect-drive inertial fusion in the US and worldwide. Since 1995, focus shifted on relativistic laser-plasma interactions and fast ignition physics fast ignition physics. Thanks to the continued funding by EURATOM, we now intensify this research both theoretically and experimentally in a number of international collaborations.