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2001
High confinement [with H 1 , ITERH- 98 y, 2 ] at b N 2.3 has been found in ASDEX Upgrade discharges with existing m, n 3, 2 neoclassical tearing modes (NTMs). The reason for the high confinement at high b N values is a transition of the NTMs into the so-called frequently interrupted regime. In this regime, the NTM growth is frequently interrupted b…
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2001
A region of zero current density in the plasma center has been observed in the advanced tokamak scenarios with off-axis lower-hybrid current drive in the JET and JT-60U tokamak experiments. Significantly, the central current density does not become negative, although this is expected based on conventional current diffusion. In this paper, it is sho…
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2001
Simultaneous current ramping and application of lower hybrid heating and current drive (LHCD) have produced a region with zero current density within measurement errors in the core of JET tokamak optimized shear discharges. The reduction of core current density is consistent with a simple physical explanation and numerical simulations of radial cur…
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2001
Relativistic electrons emit synchrotron radiation due to their gyro- and guiding-center motions in a curved magnetic field. In this article, the kinetic theory of relativistic electron beams is developed to account for radiation reaction by including the Abraham–Lorentz reaction force in the kinetic equation. As an application of this theory, the…
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2001
Detailed measurements of the rotation profile in L-mode plasmas heated by ICRF only (H minority in D), show a distinct off-axis maximum in the co-current direction. There is a slight dependence on the position of the resonance layer: the off-axis maximum in the rotation profile is modestly higher for a high field side position of the resonance laye…
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2001
Good coupling of the LH power during the whole internal transport barrier (ITB) phase has been achieved in JET by fitting the plasma shape to the LH antenna shape and by injecting CD 4 gas from a pipe near to the LH grill. No adverse effect on the edge pedestal or on the ITB quality, or significant impurity influx is observed. The key is the low io…
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2001
The RF-induced pinch of 3 He minority ions has been observed in JET affecting the diamagnetic energy, the fast ion energy content, the sawtooth period, the Alfvén eigenmode excitation and the y-emission. Further, the y-emission is consistent with RF-detrapping into co-current passing orbits. The results from the SELFO code are consistent with the …
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2000
The recent Joint European Torus deuterium-tritium campaign has yielded ion-cyclotron-resonanceheated (ICRH) pulses during which both the sawtooth characteristics and the ICRH minority ion population both evolve substantially. At multiple times during each pulse, the evolution of the kinetic-fluid MHD energy is calculated from measurement of the ene…
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2000
The islands from tearing modes driven unstable and sustained by the helically perturbed neoclassical bootstrap current often provide the practical limit to long-pulse, high confinement tokamak operation. The destabilization of such ‘‘metastable’’ plasmas depends on a ‘‘seed’’ island exceeding a threshold. A database from similar reg…
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2000
On JET the coupling resistance averaged over the four straps of the A2 antennas in the Mark II GB divertor configuration was analyzed with particular emphasis on the plasma shape dependence. The measured values were compared with models for the coupling resistance of different levels of sophistication with the ultimate goal of supplying recipes on …
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