Confinement of Fusion Reaction Products during the Fishbone Instability

Heidbrink, W. W.; Hay, R.; Strachan, J.

doi:10.1103/physrevlett.53.1905

Cited by 32 publications

(37 citation statements)

References 5 publications

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“…This theory was consistent with all experimental measurements of fastion transport at fishbones in PDX [3,[6][7][8][9][10] and could even be reconciled with the fast-ion losses observed during tangential injection in PBX [23]. White's theory does not agree well with the DIII-D data, however.…”

Section: Discussionsupporting

confidence: 49%

“…Fishbones were observed in PDX whenever the product of toroidal beta and safety factor exceeded a critical value (/3 T q ^ 2.5%) [4]. Since the instability ejected large numbers of fast ions [1,[3][4][5][6][7][8][9][10] it limited the maximum /3 achievable in PDX [4], Two main theoretical interpretations of the fishbone instability have been advanced. Chen et al [11] discovered that beam ions trapped within the q = 1 radius can kinetically destabilize a branch of the internal kink mode with frequency w = w p , where w p is the precession frequency of the resonant beam ions; they suggested that fishbones occur when the pressure of these hot, trapped beam ions (j3 M ) is sufficiently high.…”

Section: Introductionmentioning

confidence: 99%

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The fishbone instability in the DIII-D tokamak

Heidbrink

Sager

1990

Nucl. Fusion

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ABSTRACT. Although most DIII-D plasmas are stable to the fishbone instability, fishbones are sometimes observed when /3 p £ 1.5 and ^ 5 5 x 10 13 cm" 3 . These bursts are usually of minor significance operationally; however, under one condition, over 50% of the beam power was lost. The angle of beam injection has little effect on the virulence of the instability, suggesting that the fishbone instability in DIII-D is the ion diamagnetic branch of the internal kink.

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Section: Discussionsupporting

confidence: 49%

Section: Introductionmentioning

confidence: 99%

The fishbone instability in the DIII-D tokamak

Heidbrink

Sager

1990

Nucl. Fusion

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“…In PDX, reductions in 3He burnup were correlated with the amplitude of fishbone activity [361] (Fig. 57).…”

Section: Bo (Tis)mentioning

confidence: 88%

The behaviour of fast ions in tokamak experiments

1994

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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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“…Indeed, on a number of machines there has been also experimental evidence for fishbone-induced non-resonant losses of highly energetic fusion products. In the PDX tokamak, fishbones were correlated with a reduction in the burnup of 0.8 MeV 3 He ions [9]. On DIII-D, both the 1.0 MeV triton and the 3 He burnup were found to be anomalously low in the presence of fishbones [10].…”

Section: Introductionmentioning

confidence: 97%

MeV-range fast ion losses induced by fishbones on JET

et al. 2010

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Abstract. Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2-D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (E min,D ∼ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (∼ 0.5-4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (max. 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10-20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against NPA measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of nonresonant type. The simulated energy and pitch angle distribution of the losses, the ‡ See the Appendix of F. Romanelli et al., Proceedings of the 22nd IAEA Fusion Energy Conference, Geneva, Switzerland, 2008 MeV-range fast ion losses induced by fishbones on JET 2 temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.

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Confinement of Fusion Reaction Products during the Fishbone Instability

Cited by 32 publications

References 5 publications

The fishbone instability in the DIII-D tokamak

The fishbone instability in the DIII-D tokamak

The behaviour of fast ions in tokamak experiments

MeV-range fast ion losses induced by fishbones on JET

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