Abstract
The paper provides a brief introduction to the main aims, overall design philosophy and the planned parameter range of the large tokamak device (major radius R = 2.96 m; horizontal and vertical minor radii, respectively: a= 1.25 m, b = 2.10 m; plasma current, Ip= 4.8 MA), the Joint European Torus (JET), situated on the Culham Laboratory site, UK, whose main objective is to obtain and study plasmas in conditions and with dimensions approaching those needed in a fusion reactor. The main emphasis is on initial operation in the Ohmic-heating phase, in which results are presented covering a wide range of parameters: plasma currents Ip < 3.7 MA; toroidal magnetic fields BT= 1.3–3.4 T; elongation ratios b/a= 1.2–1.7; and safety factor values, q = 2.3–10. Average electron densities ne = (1–4) X 1019m−3, with high central electron temperatures (Te up to 5 keV) and ion temperatures (Ti up to 3 keV) have been achieved, although Zeff was in the range of 2.4–10. Energy confinement times (τE) of up to 0.8 s have been obtained. Some problems with metallic and low-Z impurities are noted, causing high radiation levels. Initial experiments, with ion cyclotron resonance frequency (ICRF) heating of H and 3He minorities in deuterium plasmas at MW levels, are reported. The paper concludes with a description of planned future experiments on impurity control, additional heating (ICRF ≈ 15 MW, and neutral injection ≈ 10 MW), and preparations for tritium operation.