Analysis of second harmonic ICRF waves in NBI heated JT-60 plasmas

Hamamatsu, K.; Azumi, M.; Kishimoto, Y.; Fukuyama, A.; Itoh, Sanae I.; Itoh, K.

doi:10.1088/0029-5515/29/2/001

Cited by 16 publications

(15 citation statements)

References 12 publications

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“…However, tail temperatures were almost the same for the third and fourth harmonics. The dependence of the tail temperature on the harmonic number was found to be in qualitative agreement with results from a simulation code analysis based upon the 1-D Fokker-Planck equation coupled with the kinetic wave equation [31]. However, the experimental tendency of the tail ion stored energy showed that the response to the level of absorbed ICRF power is much stronger than the response to the harmonic number.…”

Section: Neutral Particle Analysis In the Megaelectronvolt Rangesupporting

confidence: 76%

Alfvén eigenmode and energetic particle research in JT-60U

Kimura¹,

Kusama²,

Saigusa³

et al. 1998

Nucl. Fusion

146

127

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Recent results on investigations of Alfvén eigenmodes, fast ion confinement and fast ion diagnostics in JT-60U are presented. It was found that toroidicity induced Alfvén eigenmodes (TAEs) were stable in negative shear discharges with a large density gradient at the internal transport barrier (ITB). If the density gradient was small at the ITB, multiple TAEs appeared around the q = 2 surface (pitch minimum) and showed a large frequency chirping (∆f ≈ 80 kHz). In low-q positive shear discharges, the location of the TAEs changed from outside to inside the q = 1 surface, owing to a temporal change of the q profile. A significant depression of the megaelectronvolt ion population was observed only with high-n (n up to 14) multiple TAEs inside the q = 1 surface. Non-circular triangularity induced Alfvén eigenmodes were observed for the first time. Considerable depression of the triton burnup was observed in negative shear discharges. Orbit following Monte Carlo simulations indicated that ripple loss was responsible for the enhanced triton losses. The fast ion stored energies in ICRF heated negative shear discharges were comparable to those of positive shear plasmas. Tail ion temperatures in high (second to fourth) harmonic ICRF heating experiments were first analysed with an MeV neutral particle analyser. The behaviour of MeV ions produced by ICRF heating was studied with gamma ray diagnostics. A scintillating fibre detector system for detecting the 14 MeV neutron emission was developed for the triton burnup studies. Ion cyclotron emission measurements discriminating between parallel and perpendicular components of the electric field were carried out for the first time.

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Section: Neutral Particle Analysis In the Megaelectronvolt Rangesupporting

confidence: 76%

Alfvén eigenmode and energetic particle research in JT-60U

Kimura¹,

Kusama²,

Saigusa³

et al. 1998

Nucl. Fusion

146

127

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“…We evaluate the incremental stored energy by beam acceleration, employing a one-dimensional selfconsistent code which takes into account the global wave structure and the quasi-linear velocity space diffusion. Details of the calculation are described in Refs [15,16]. The calculated incremental stored energy of the beam component is about 200 kJ, which is in reasonable agreement with the experiment.…”

Section: Icrf 'supporting

confidence: 72%

Experimental study on beam acceleration with combined NBI heating and second-harmonic ICRF heating in JT-60

Kimura¹,

Fujii²,

Tobita³

et al. 1991

Nucl. Fusion

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Beam acceleration by heating in the second-harmonic ion cyclotron range of frequency (ICRF) in combination with heating by hydrogen neutral beam injection (NBI) was investigated in the JT-60 tokamak. The energy spectra of the accelerated fast ions were measured by a charge exchange neutral energy analyser whose line of sight was intersected by specific beam lines in the plasma core in order to obtain the required information. The dependences of the tail ion temperature on various parameters (electron density, NBI power and the toroidal phasing of the antenna) were examined. Optimized conditions for beam acceleration were evaluated. For combined ICRF heating and NBI heating, an incremental energy confinement time of 210 ms was achieved, which was three times higher than that obtained with NBI heating alone or with ICRF heating alone. This improvement of the energy confinement during combined NBI and ICRF heating can be explained by a build-up of the fast ions accelerated by the ICRF wave. The scaling of the incremental energy confinement time during combined ICRF+NBI heating was obtained.

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“…Anisotropy in velocity space is approximated using formulas suggested by Hammett [34]. The Fokker-Planck equation for the distribution function f is solved in terms of the energy W ; the most important terms in the equation are the beam source, the collisional drag on electrons and thermal ions, and the angle averaged quasi-linear RF diffusion operator [35],…”

Section: Predicted Neutron Enhancementmentioning

confidence: 99%

High harmonic ion cyclotron heating in DIII-D: Beam ion absorption and sawtooth stabilization

et al. 1999

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Abstract. Combined neutral beam injection and fast wave heating at the fourth cyclotron harmonic produce an energetic deuterium beam ion tail in the DIII-D tokamak. When the concentration of thermal hydrogen exceeds ∼5%, the beam ion absorption is suppressed in favour of second harmonic hydrogen absorption. As theoretically expected, the beam absorption increases with beam ion gyroradius; also, central absorption at the fifth harmonic is weaker than central absorption at the fourth harmonic. For central heating at the fourth harmonic, an energetic, perpendicular, beam population forms inside the q = 1 surface. The beam ion tail transiently stabilizes the sawtooth instability but destabilizes toroidicity induced Alfvén eigenmodes (TAEs). Saturation of the central heating correlates with the onset of the TAEs. Continued expansion of the q = 1 radius eventually precipitates a sawtooth crash; complete magnetic reconnection is observed.

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Analysis of second harmonic ICRF waves in NBI heated JT-60 plasmas

Cited by 16 publications

References 12 publications

Alfvén eigenmode and energetic particle research in JT-60U

Alfvén eigenmode and energetic particle research in JT-60U

Experimental study on beam acceleration with combined NBI heating and second-harmonic ICRF heating in JT-60

High harmonic ion cyclotron heating in DIII-D: Beam ion absorption and sawtooth stabilization

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