JT-60SA superconducting magnet system

International audienceThe JT-60SA experiment is one of the three projects to be undertaken in Japan as part of the Broader Approach Agreement, conducted jointly by Europe and Japan, and complementing the construction of ITER in Europe. The superconducting magnet system for JT-60SA consists of 18 Toroidal Field (TF) coils, a Central Solenoid (CS) and six Equilibrium Field (EF) coils. The TF magnet generates the field to confine charged particles in the plasma, the CS provides the inductive flux to ramp up plasma current and contribute to plasma shaping and the EF coils provide the position equilibrium of plasma current and the plasma vertical stability. The six EF coils are attached to the TF coil cases through supports with flexible plates allowing radial displacements. The CS assembly is supported from the bottom of the TF coils through its pre-load structure. The design status of the JT-60SA superconducting magnetic system is reviewed

Lower Hybrid Current Drive in Tore Supra and Jet

Recent Lower Hybrid Current Drive (LHCD) experiments in TORE SUPRA and JET are reported. Large multijunction launchers have allowed the coupling of 5 MW to the plasma for several seconds with a maximum of 3.8 kw/cm2. Measurements of the scattering matrices of the antennae show good agreement with theory. The current drive efficiency in TORE SUPRA is about 0.2 x 10(20) Am-2/W with LH power alone and reaches 0.4 x 10(20) Am-2/W in JET thanks to a high volume-averaged electron temperature (1.9 keV) and also to a synergy between Lower Hybrid and Fast Magnetosonic Waves. At N(e)BAR = 1.5 x 10(19) m-3 in TORE SUPRA, sawteeth are suppressed and m = 1 MHD oscillations the frequency of which clearly depends on the amount of LH power are observed on soft x-rays, and also on non-thermal ECE. In JET ICRH produced sawtooth-free periods are extended by the application of LHCD (2.9 s. with 4 MW ICRH) and current profile broadening has been clearly observed consistent with off-axis fast electron populations. LH power modulation experiments performed in TORE SUPRA at N(e)BAR = 4 x 10(19) m-3 show a delayed central electron heating despite the off-axis creation of suprathermal electrons, thus ruling out the possibility of a direct heating through central wave absorption. A possible explanation in terms of anomlous fast electron transport and classical slowing down would yield a diffusion coefficient of the order of 10 m2/s for the fast electrons. Other interpretations such as an anomalous heat pinch or a central confinement enhancement cannot be excluded. Finally, successful pellet fuelling of a partially LH driven plasma was obtained in TORE SUPRA, 28 successive pellets allowing the density to rise to N(e)BAR = 4 x 10(19) m-3. This could be achieved by switching the LH power off for 90 ms before each pellet injection, i.e. without modifying significantly the current density profile

Development of RF heating and current drive systems for long pulse operation on Tore Supra

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