Transition between Isotope-Mixing and Nonmixing States in Hydrogen-Deuterium Mixture Plasmas

Ida, K.; Nakata, M.; Tanaka, Kaoru; Yoshinuma, M.; Fujiwara, Y.; Sakamoto, R.; Motojima, G.; Masuzaki, S.; Kobayashi, Tatsuya; Yamasaki, K.

doi:10.1103/physrevlett.124.025002

Cited by 21 publications

(23 citation statements)

References 21 publications

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“…This is in stark contrast with the electron particle transport, which governs the electron density profile and is characterised by transport coefficients an order of magnitude smaller than those for the ions. In TEM mode (not the case in these experiments), the ion transport coefficients from gyrokinetic modelling would be much smaller and isotope mixing is expected to be considerably slower as observed in LHD (Ida et al 2020). Core isotope ratio control has also been demonstrated by shallow (low penetration) deuterium pellets injected into a plasma simultaneously fuelled by hydrogen gas and hydrogen NBH (Valovic et al 2019).…”

Section: Transport In Mixed Isotope Elmy H-modesmentioning

confidence: 92%

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Isotope dependence of energy, momentum and particle confinement in tokamaks

Weisen

Maggi²,

Oberparleiter³

et al. 2020

J. Plasma Phys.

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The isotope dependence of plasma transport will have a significant impact on the performance of future D-T experiments in JET and ITER and eventually on the fusion gain and economics of future reactors. In preparation for future D-T operation on JET, dedicated experiments and comprehensive transport analyses were performed in H, D and H-D mixed plasmas. The analysis of the data has demonstrated an unexpectedly strong and favourable dependence of the global confinement of energy, momentum and particles in ELMy H-mode plasmas on the atomic mass of the main ion species, the energy confinement time scaling as ${\tau _E}\sim {A^{0.5}}$ (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045; JET Team, Nucl. Fusion, vol. 39, 1999, pp. 1227–1244), i.e. opposite to the expectations based only on local gyro-Bohm (GB) scaling, ${\tau _E}\sim {A^{ - 0.5}}$ , and stronger than in the commonly used H-mode scaling for the energy confinement (Saibene et al., Nucl. Fusion, vol. 39, 1999, 1133; ITER Physics Basis, Nucl. Fusion, vol. 39, 1999, 2175). The scaling of momentum transport and particle confinement with isotope mass is very similar to that of energy transport. Nonlinear local GENE gyrokinetic analysis shows that the observed anti-GB heat flux is accounted for if collisions, E × B shear and plasma dilution with low-Z impurities (9Be) are included in the analysis (E and B are, respectively the electric and magnetic fields). For L-mode plasmas a weaker positive isotope scaling ${\tau _E}\sim {A^{0.14}}$ has been found in JET (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045), similar to ITER97-L scaling (Kaye et al., Nucl. Fusion, vol. 37, 1997, 1303). Flux-driven quasi-linear gyrofluid calculations using JETTO-TGLF in L-mode show that local GB scaling is not followed when stiff transport (as is generally the case for ion temperature gradient modes) is combined with an imposed boundary condition taken from the experiment, in this case predicting no isotope dependence. A dimensionless identity plasma pair in hydrogen and deuterium L-mode plasmas has demonstrated scale invariance, confirming that core transport physics is governed, as expected, by the 4 dimensionless parameters ρ*, ν*, β, q (normalised ion Larmor radius, collisionality, plasma pressure and safety factor) consistently with global quasi-linear gyrokinetic TGLF calculations (Maggi et al., Nucl. Fusion, vol. 59, 2019, 076028). We compare findings in JET with those in different devices and discuss the possible reasons for the different isotope scalings reported from different devices. The diversity of observations suggests that the differences may result not only from differences affecting the core, e.g. heating schemes, but are to a large part due to differences in device-specific edge and wall conditions, pointing to the importance of better understanding and controlling pedestal and edge processes.

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Section: Transport In Mixed Isotope Elmy H-modesmentioning

confidence: 92%

“…2018) as observed in LHD (Ida et al . 2020). Core isotope ratio control has also been demonstrated by shallow (low penetration) deuterium pellets injected into a plasma simultaneously fuelled by hydrogen gas and hydrogen NBH (Valovic et al .…”

Section: Isotope Dependence In Jet-ilw Type I Elmy H-modesmentioning

confidence: 99%

Isotope dependence of energy, momentum and particle confinement in tokamaks

Weisen

Maggi²,

Oberparleiter³

et al. 2020

J. Plasma Phys.

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“…In a multiion plasma the different ions can interchange at different timescales to the electron particle transport. The opposite relation holds for TEM dominated regimes, as shown experimentally in the Large Helical Device (LHD) [19].…”

Section: Introductionmentioning

confidence: 92%

Multiple-isotope pellet cycles captured by turbulent transport modelling in the JET tokamak

et al. 2021

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For the first time the pellet cycle of a multiple-isotope plasma is successfully reproduced with reduced turbulent transport modelling, within an integrated simulation framework. Future nuclear fusion reactors are likely to be fuelled by cryogenic pellet injection, due to higher penetration and faster response times. Accurate pellet cycle modelling is crucial to assess fuelling efficiency and burn control. In recent JET tokamak experiments, deuterium pellets with reactorrelevant deposition characteristics were injected into a pure hydrogen plasma. Measurements of the isotope ratio profile inferred a Deuterium penetration time comparable to the energy confinement time. The modelling successfully reproduces the plasma thermodynamic profiles and the fast deuterium penetration timescale. The predictions of the reduced turbulence model QuaLiKiz in the presence of a negative density gradient following pellet deposition are compared with GENE linear and nonlinear higher fidelity modelling. The results are encouraging with regard to reactor fuelling capability and burn control.

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“…The transition from non-mixing to mixing state was experimentally observed in the hydrogen and deuterium (H-D) mixture plasma in LHD [163]. In this experiment, the radial profiles of density ratio of hydrogen to deuterium were measured with bulk charge exchange spectroscopy [164].…”

Section: Isotope Mixing Beyond Diffusive/non-diffusive Modelmentioning

confidence: 95%

“…Radial profiles of (a) electron density, (b) electron and ion temperature, hydrogen density fraction before (non-mixing state) and after (isotope-mixing state), (c) hydrogen pellet, and (d) deuterium pellet injection (fromFigure 6(a)(b) andFigure 4in[163]). …”

mentioning

confidence: 99%

Bifurcation phenomena in magnetically confined toroidal plasmas

Ida

2020

Advances in Physics: X

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Bifurcation phenomena observed in turbulence and transport, in topology of magnetic field and MHD, and the interplay between turbulence and MHD bifurcation in magnetically confined toroidal plasmas are reviewed. Two types of bifurcation phenomena in turbulent transport are discussed. One is significant change in the magnitude of the diffusion term and the other is a sign flip of non-diffusive term of transport. The bifurcation of diffusion term magnitude causes the transition to a so-called improved mode such as ion-electron root transition, L-mode to H-mode transition, and ITB formation. In contrast, the bifurcation of non-diffusion term sign causes the intrinsic flow reversal, convection reversal of bulk ion, and impurity ions. Two types of bifurcation phenomena in MHD are discussed. One is the bifurcation of static magnetic topology and the other is the bifurcation of MHD instability. The bifurcation of static magnetic topology is observed in between three magnetic topology (nested magnetic flux surface, magnetic island and stochastic magnetic field) in toroidal plasma. The bifurcation of MHD instability is observed as a parity change of MHD oscillation. The bifurcation of the magnetic island states caused by the interplay between turbulence and MHD is also discussed.

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Transition between Isotope-Mixing and Nonmixing States in Hydrogen-Deuterium Mixture Plasmas

Cited by 21 publications

References 21 publications

Isotope dependence of energy, momentum and particle confinement in tokamaks

Isotope dependence of energy, momentum and particle confinement in tokamaks

Multiple-isotope pellet cycles captured by turbulent transport modelling in the JET tokamak

Bifurcation phenomena in magnetically confined toroidal plasmas

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