ABSTRACT.Reactor relevant ICRH scenarios have been assessed during D-T experiments on the JET tokamak using H-mode divertor discharges with ITER-like shapes and safety factors. Deuterium minority heating in tritium plasmas was demonstrated for the first time. For 9% deuterium, an ICRH power of 6 MW gave 1.66 MW of fusion power from reactions between suprathermal deuterons and thermal tritons. The Q-value of the steady state discharge reached 0.22 for the length of the RF flat top (2.7 s), corresponding to three plasma energy replacement times. The Doppler broadened neutron spectrum showed a deuteron energy of 125 keV which was optimum for fusion and close to the critical energy. Thus strong bulk ion heating was obtained at the same time as high fusion efficiency. Deuterium fractions around 20% produced the strongest ion heating together with a strong reduction of the suprathermal deuteron tail. The edge localised modes (ELMs) had low amplitude and high frequency and each ELM transported less plasma energy content

The effect of bulk ion heating in Tore Supra has been investigated by studying discharges with varying concentrations of minority ions during ICRF hydrogen minority heating in deuterium/ 4 He plasmas. As expected, the level of bulk ion heating is found to increase with the minority concentration. Higher levels of ion heating are shown to be accompanied by two significant effects: an improved energy confinement and a strong influence on the plasma rotation.

Ion cyclotron resonance heating (ICRH) experiments have been carried out in JET D-T plasmas using scenarios applicable to reactors. Deuterium minority heating in tritium plasmas is used for the first time and produces 1.66 MW of D-T fusion power for an ICRH power of 6 MW. The Q value is 0.22, which is a record for steady state discharges. Fundamental He 3 minority ICRH, in both 50:50 D-T and tritium dominated plasmas, generates strong bulk ion heating and ion temperatures up to 13 keV. Second harmonic tritium ICRH is seen to heat mainly the electrons as expected for JET conditions. All three schemes produce H-mode plasmas. [S0031-9007(98)06143-2] PACS numbers: 52.50. Gj, 52.55.Fa, 52.55.Pi Ion cyclotron resonance heating is the only method of heating majority ions, rather than electrons, in the dense core of a tokamak reactor. Radiofrequency (rf) power is used to excite a fast magnetosonic wave, to which the high density plasma is accessible. The wave is absorbed at a cyclotron resonance which is positioned in major radius (usually the plasma center) by the choice of magnetic field and rf frequency. The ions damping the wave are often accelerated to suprathermal energies, especially if they are a minority species. This energy is then transferred to the thermal ions and electrons by Coulomb collisions. If the energy of the absorbing ions is less than a critical value, power flows mainly to the thermal ions rather than to the electrons. The critical energy at which the power to the electrons equals that to the ions is given [1] by E crit 14.8AT e ͓Sn j Z 2 j ͞n e A j ͔ 2͞3 where A is the atomic mass of the energetic ions, n e is the electron density, Z is the atomic number, the sum is over the thermal ion species, and T e is the electron temperature. For fast deuterons in a tritium plasma, E crit 14.2T e . In the JET D-minority experiments, T e is about 7 keV and E crit ഠ 100 keV, which is also the deuteron energy at which the deuterium-tritium (D-T) fusion cross section peaks. High fusion power is thus achieved at the same time as equal ion and electron heating.Several ion cyclotron resonance heating (ICRH) schemes in D-T plasmas have been included in the design of the JET system [2] which thus covers a wide frequency band, 23-57 MHz. The same schemes are being considered for the ITER reactor [3]. Three of these scenarios are minority deuterium and minority He 3 at their fundamental resonances and majority tritium at its second harmonic resonance. Recent calculations [4,5] for ITER predict that each method can produce more than 50% ion heating on the route to ignition. The present experiments have demonstrated and assessed the fundamental deuterium scheme, which has never been used previously. Also, the physics and performance of all three methods have been studied for the first time in H mode, D-T plasmas heated predominantly by ICRH. The plasmas were similar to those expected in ITER in terms of shape, safety factor ͑q͒, normalized confinement time, and the behavior of edge localized modes (ELMs), which affec...

The toroidal field coils in Tore Supra are supra-conducting, and their number is restricted to 18. As a result, the ripple is fairly large, about 7% at the plasma boundary. Tore Supra has consequently been equipped with dedicated ripple loss diagnostics, which has allowed ripple loss studies. This paper reports on the measurements made with these diagnostics and provides an analysis of the experimental results, comparing them with theoretical expectations whenever possible. Furthermore, the main heating source accelerating ions in Tore Supra is ion cyclotron resonance range of frequency (ICRF) heating, and the paper provides new information on the ripple losses of ICRF accelerated ions.