Andrea Murari Guido Vagliasindi Sebastiano De Fiore Eleonora Arena Paolo Arena Luigi Fortuna Y. Andrew M. Johnson JET-EFDA Contributors
Dynamical systems are often considered immune from memory effects, i.e., the dependence of their time evolution on the previous history. This assumption has been tested for two phenomena in nuclear fusion that are believed to sometimes show sensitivity to the previous history of the discharge: disruptions and the transition from the L mode to the H…
PublishedJ. P. Graves I. Chapman S. Coda L.-G. Eriksson T. Johnson
The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q 1/4 1 surface resides within a narrow…
PublishedM. J. Mantsinen L.C. Ingesson T. Johnson V.G. Kiptily M.-L. Mayoral S. E. Sharapov B. Alper L. Bertalot S. Conroy L.-G. Eriksson T. Hellsten J.-M. Noterdaeme S. Popovichev E. Righi A. A. Tuccillo
Experiments on the JET tokamak show that the wave-induced pinch in the presence of toroidally asymmetric waves can provide a tool for controlling the profile of ion-cyclotron-resonant 3 He ions. Direct evidence for the wave-induced pinch has been obtained from the measured -ray emission profiles. Concurrent differences in the excitation of Alfve?n …
PublishedT. Johnson T. Hellsten M. Mantsinen V. Kiptily S. Sharapov et al.
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 …
PublishedR. A. Pitts
This paper compares the form of f(v||) arising from the warm-ion, kinetic models of Emmert et al. [ Phys. Fluids 23, 803 ( 1980) ] and Bissel and Johnson [ Phys. Fluids 30,779 ( 1987) ] with experimentally measured distributions from the DITE tokamak obtained with a retarding field analyzer (RFA). The results show that the commonl…
PublishedJ. D. Johnson A. J. T. Holmes
One problem inherent in the use of small planar Langmuir probes to analyze low-density plasma is expansion of the space-charge sheath with increased probe potential due to the departure from planarity caused by a nonnegligible sheath edge. Experimental evidence showing the existence of significant edge effects in the ion saturation region of the ch…
PublishedA. W. Morris T. C. Hender J. Hugill P. S. Haynes P. C. Johnson B. Lloyd D. C. Robinson et al.
Magnetic feedback control has been used in the DITE tokamak to substantially reduce saturated m = 2, n = 1 instabilities in both Ohmic discharges and discharges with lower-hybrid current drive (LHCD). Feedback has been used for the first time to significantly increase the disruptive density limit in a tokamak. LHCD on DITE stabilizes the sawtooth i…
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