The Joint European Torus (JET) is the largest single project of the nuclear fusion research programme of the European Atomic Energy Community (EURATOM). The project was designed with the essential objective of obtaining and studying plasma in conditions and with dimensions approaching those needed in a fusion reactor. The studies are aimed at: a) investigating plasma processes and scaling laws as plasma dimensions and parameters approach those necessary for a fusion reactor; b) examining and controlling plasma-wall interactions and impurity influxes in near-reactor conditions; c) demonstrating effective heating techniques, capable of approaching reactor temperatures in JET, in the presence of the prevailing loss processes (particularly, R.F. and Neutral Beam Heating processes); d) studying alpha-particle production, confinement and subsequent plasma interaction and heating produced as a result of fusion between deuterium and tritium.