ITER is an international tokamak (magnetic confinement fusion) experiment, planned to be built in France and designed to show the scientific and technological feasibility of a full-scale fusion power reactor. It builds upon research conducted on devices such as DIII-D, TFTR, JET, JT-60, and T-15, and will be considerably larger than any of them. The program is anticipated to last for 30 years—10 years for construction, and 20 years of operation—and cost approximately €10 billion ($12.1 billion), making it the second most expensive scientific project after the International Space Station. After many years of deliberation, the participants announced in June 2005 that ITER will be built in Cadarache, France.
According to the ITER consortium, fusion power offers the potential of "environmentally benign, widely applicable and essentially inexhaustible"  electricity, properties that they believe will be needed as world energy demands increase while simultaneously greenhouse gas emissions must be reduced, justifying the expensive research project.
ITER is designed to produce approximately 500 MW (500,000,000 watts) of fusion power sustained for up to 500 seconds (compared to JET's peak of 16 MW for less than a second). It is a significant amount of power for a fusion research project; a future fusion power plant would generate about 3000-4000 MW of thermal power. Although ITER will produce net power in the form of heat, the generated heat will not be used to generate any electricity.
ITER was originally an acronym standing for International Thermonuclear Experimental Reactor; that title was dropped to avoid the negative popular connotations of 'thermonuclear' and 'experimental'. 'Iter' also means 'the way' in Latin, and this double meaning reflects ITER's role in harnessing nuclear fusion as a peaceful power source.
ITER is intended to be an experimental step between today's studies of plasma physics and future electricity-producing fusion power plants. It is technically ready to start construction and the first plasma operation is expected in 2016.
The official objective of ITER is to "demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes". ITER has a number of specific objectives, all concerned with developing a viable fusion power reactor:
To momentarily produce ten times more thermal energy from fusion heating than is supplied by auxiliary heating (a Q value of 10). To produce a steady-state plasma with a Q value of greater than 5. To maintain a fusion pulse for up to eight minutes. To ignite a 'burning' (self-sustaining) plasma. To develop technologies and processes needed for a fusion power plant—including superconducting magnets and remote handling (maintenance by robot). To verify tritium breeding concepts.