Non-linear power conversion by non-resonant parametric decay of the fast wave during ICRF heating

Heikkinen, Jukka; Khare, Avinash

doi:10.1088/0029-5515/29/8/007

Cited by 12 publications

(7 citation statements)

References 14 publications

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“…However, on the basis of these observations the parametric decay waves are not considered.to have a major influence on impurity release in the present experiments. They may contribute, but theoretical estimates [34] indicate that the power transferred from fast waves to decay waves is negligible. Cyclotron absorption by impurity ions in front of the screen does not seem to play any appreciable role because there was no difference at all in nickel release when the magnetic field was changed from 2.1 T to 2.25 T. This change corresponds to a displacement of the cyclotron harmonic layers of impurities, mainly carbon, by a large factor.…”

Section: Discussionmentioning

confidence: 99%

Role of the antenna screen angle during ICRF heating in JET

et al. 1990

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Two comparative heating experiments were carried out to test the role of the antenna screen angle during high power ICRF heating in JET. In the first experiment the magnetic field was practically aligned with the screen elements, whereas in the second experiment the toroidal field was reversed and the angle between the elements and the field was 25°. There were clear differences in the impurity influx, the heating efficiency and the coupling resistance between discharges with normal field and discharges with reversed field. The results indicate the impact of the Faraday screen design on the levels of RF enhanced metal influxes originating at the screen. This should be of particular relevance for the ICRF antennas in a reactor where, in contrast to small devices, most of the interaction between the RF fields and the plasma edge is expected to take place around the antenna structures because of the highly localized RF field patterns. A numerical code based on three-dimensional single-pass and full wave calculations of antenna-plasma coupling, including an arbitrary angle between the screen elements and the magnetic field, can qualitatively reproduce the observed difference in the coupling resistance. The experimental results are discussed with regard to possible mechanisms that can account for the observed differences in the two cases studied.

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Section: Discussionmentioning

confidence: 99%

Role of the antenna screen angle during ICRF heating in JET

et al. 1990

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“…The same type of instabilities was found on TEXTOR ( VAN NrEuwENHOvE et al, 1988b) for plasma and heating conditions differing from those in ASDEX, and on other Tokamaks such as JET (BURES rt al., 1988) and JT-60 (FUJI cf al., 1990). Signals at half-harmonics of the generator frequency were detected in the D(H) and 3He(H) minority heating schemes on TEXTOR (VAN NIEuwENHovE ef al., 1988b) and later on JET (HEIKKINEN and AVINASH, 1989).…”

mentioning

confidence: 98%

Nonlinear wave phenomena measured by capacitive probes during auxiliary heating in the SOL of TEXTOR

Bora¹,

Nieuwenhove²,

Oost³

1991

Plasma Phys. Control. Fusion

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Measurements of different wwe phenomena at the plasma boundary during auxiliary heating (ICRH and combined JCRH-NBI) experiments on TEXTOR were performed to elucidate some of the mcchanisms responsible for ICRF-induced effects on the edgc plasma and on plasma-wall interactions. Capacitive probes capable of withstanding high heat loads were used. Excited waves were studied during carbonized and boronized wall conditions in TEXTOR. Apart from at the r.f. generator frcquency, waves were also detected at thc harmonic frequencies due to sheath effeas 81 thc ICRF antenna. Furthermore. waves at half-harmonic frequencies were also excited under Certain conditions. During carbonized machine operation conditions, wares at half-harmonic frequencies were always observed except during thc combined healing phase. Under normal boronized opcration generally no waves at half-harmonic frequencies wcre observed during neutral beam-ICRH combined heating of deuterium plasma. Howevcr, waves at halfharmonic frequencies were observed at higher toroidal magnetic field values as well as during D neutral beam-ICRH combined heating at high H concentration and high r.f. power. Wave amplitudes at the different frequencies were studied as a function of different plasma and machine parametcrs.

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“…This is going to be achieved, however, through the usage of the bispectral analysis. The fact that ICRH undergoes a PDI is not new and was studied theoretically [22,23] and reported by different authors [24][25][26][27] using RF probes. However, most if not all of the experiments focused on the PDI leading high-frequency oscillations of the order of the pump wave.…”

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confidence: 99%

On the interaction between the ion cyclotron resonance heating and scrape-off layer turbulence via coherent waves

2014

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It was reported on the ASDEX-Upgrade tokamak and recently confirmed on the Tore Supra tokamak (Antar 2010 et al Phys. Rev. Lett. 105 165001, Antar 2012 Nucl. Fusion 52 103005) that ion cyclotron resonance heating (ICRH) reduces turbulence in the scrape-off layer (SOL) by strongly affecting the large intermittent structures. In this paper, and for the first time, we show that ICRH, with a frequency at 57 MHz, excites waves at frequencies about 1.7 MHz as a consequence of parametric decay instability. This is reflected in the power spectra of the ion saturation signals, measured by fixed Langmuir probes acquired at 200 MHz, as well as in the cross-correlation between two toroidally distanced probes and in the bicoherence spectra. The velocity and the wavenumber of this perturbation is determined indicating that they may be ion sound waves. Furthermore, it is shown that they are nonlinearly coupled to the turbulent fluctuations leading to the strong modification of the power spectrum and could provide explanations about the decrease in the level of turbulence in the SOL during ICRH. This aspect is reflected in the enhanced three-wave coupling between these waves and turbulence studied by applying the bispectral analysis. Turbulence appears thus to be affected when ICRH is applied by the intermediate of ion sound waves.

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Non-linear power conversion by non-resonant parametric decay of the fast wave during ICRF heating

Cited by 12 publications

References 14 publications

Role of the antenna screen angle during ICRF heating in JET

Role of the antenna screen angle during ICRF heating in JET

Nonlinear wave phenomena measured by capacitive probes during auxiliary heating in the SOL of TEXTOR

On the interaction between the ion cyclotron resonance heating and scrape-off layer turbulence via coherent waves

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