Observation of parametric decay correlated with edge heating using an ion Bernstein wave antenna on DIII-D

ABSTRACT. Fast ions with energies significantly larger than the bulk ion temperature are used to heat most tokamak plasmas. Fast ion populations created by fusion reactions, by neutral beam injection and by radiofrequency (RF) heating are usually concentrated in the centre of the plasma. The velocity distribution of these fast ion populations is determined primarily by Coulomb scattering; during wave heating, perpendicular acceleration by the RF waves is also important. Transport of fast ions is typically much slower than thermal transport, except during MHD events. Intense fast ion populations drive collective instabilities. Implications for the behaviour of alpha particles in future devices are discussed.

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“…On DIII-D, formation of a tail in the plasma edge was correlated with parametric decay of the ion Bernstein waves [156].…”

Section: Ion Cyclotron Range Of Frequenciesmentioning

confidence: 99%

The behaviour of fast ions in tokamak experiments

1994

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“…Different results were obtained in more recent IBW experiments. No plasma heating and confinement improvement were found during the experiments carried out on DIII-D [20,21] and TFTR [22]. In the JIPP2-U [23] and PBX-M [14] experiments, an improvement of confinement was found.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the heating scenarios of the ion Bernstein wave (IBW) experiment in Frascati Tokamak Upgrade

et al. 2002

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Ion Bernstein waves (IBWs) have been proposed as useful for heating and improving transport in tokamak plasmas. The experiments carried out so far have not provided a sufficient assessment of this concept, due to the occurrence of parasitic phenomena that caused poor reproducibility of IBW heating and confinement effects. An experiment on FTU has given the first test of IBW coupling to a tokamak plasma by a waveguide antenna utilized in place of the standard dipole antenna. In addition, the experiment operates at a high frequency that is expected to reduce the non-linear wave-plasma interaction at the edge. These phenomena were considered to be the cause of the lack of RF power penetration in the plasma bulk and of the production of impurity influx. The possible IBW experimental scenarios expected for the FTU plasma are described. To perform this analysis, quasi-linear and non-linear models are utilized for the wave propagation, damping and turbulence suppression suitable for transport barrier formation. As a result of this study, FTU is expected to be a useful facility for testing the IBW concept for advanced tokamaks.

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“…When this instability occurred, tails formed in the hydrogen and deuterium distribution functions; the magnitude of the tail correlated with the amplitude of the parametric decay instability. 14 Subsequently, the IBW antennas were replaced by fast-wave antennas. Fast waves with frequencies of 60 to 120 MHz accelerate injected deuterium beam ions.…”

Section: Iib Icrf Accelerationmentioning

confidence: 99%