The Joint European Torus: installation, first results and prospects

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, I p = 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 Ohmicheating phase, in which results are presented covering a wide range of parameters: plasma currents I p < 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 n e = (1-4) X 10 19 m~3, with high central electron temperatures (T e up to 5 keV) and ion temperatures (Tj up to 3 keV) have been achieved, although Z e ff was in the range of 2.4-10. Energy confinement times (T E ) 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 3 He 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.

Predictive simulations of ITER including neutral beam driven toroidal rotation

“…7. In this ITER simulation, the GLF23 model is used with 20 helium ash density after each sawtooth crash. Although the sawtooth crashes periodically affect the distribution of helium ash, the plasma profiles recover very rapidly ͑in about 1 s͒, as shown in Fig.…”

“…5. In addition, the GLF23 model for toroidal rotation has been tested against experimental data from Joint European Torus 20 ͑JET͒ discharges in JETTO simulations, in which the torque was computed using the PENCIL code ͑see Ref. 21͒.…”

Modeling of dust-particle behavior for different materials in plasmas

“…Table I lists the materials used for plasma facing components ͑PFC͒ in different fusion devices around the world and in ITER. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] As seen, the commonly used materials are Be, C, Fe, Mo, and W. The choice of material in current devices is typically governed by specific thermochemical characteristics in hydrogen plasma environment, cost, and suitable construction properties as well as by plasma performance considerations. Note that boron was widely used in recent fusion plasma experiments as the restorable coating of PFCs.…”

Superdense core mode in the Large Helical Device with an internal diffusion barrier

“…The pellet enhanced performance ͑PEP͒ mode 16 was achieved in the Joint European Torus. 17 In the PEP mode, central deposition from pellet fueling and central heating in the ion cyclotron range of frequencies can lead to strongly peaked density profiles that produce the ITBs with the negative shear region in the plasma core. 18,19 In the Wendelstein stellarator ͑W7-AS͒, 20 another improved confinement mode called the high-density H-mode ͑HDH͒ was achieved, which is characterized by flat density profiles and low impurity confinement time.…”