Isotope and fast ions turbulence suppression effects: Consequences for high-β ITER plasmas

García, J.; Görler, T.; Jenko, F.

doi:10.1063/1.5016331

Cited by 50 publications

(76 citation statements)

References 23 publications

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“…For higher density discharges, such as H-modes, the different beam penetration could bring to a different situation. In general, fast ions can play an important role for the stabilization of the turbulent ion heat transport in the plasma core (and might play a role also in ITER [52]) and they can contribute significantly to the total plasma pressure.…”

Section: Discussionmentioning

confidence: 99%

Role of fast ion pressure in the isotope effect in JET L-mode plasmas

et al. 2019

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This paper presents results of JET ILW L-mode experiments in hydrogen (H) and deuterium (D) plasmas, dedicated to the study of the isotope dependence of ion heat transport by determination of the ion critical gradient and stiffness by varying the ICRH power deposition. When no strong role of fast ions in the plasma core is expected, the main difference between the two isotope plasmas is determined by the plasma edge and the core behavior is consistent with a gyro-Bohm scaling. When the heating power (and the fast ion pressure) is increased, in addition to the difference in the edge region, also the plasma core shows substantial changes. The stabilization of ion heat transport by fast ions, clearly visible in D plasmas, appears to be weaker in H plasmas, resulting in a higher ion heat flux in H with apparent anti-gyro-Bohm mass scaling. The difference is found to be caused by the different fast ion pressure between H and D plasmas, related to the heating power settings and to the different fast ion slowing down time, and is completely accounted for in non-linear gyrokinetic simulations. The application of the TGLF quasi-linear model to this set of data is also discussed.

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Section: Discussionmentioning

confidence: 99%

Role of fast ion pressure in the isotope effect in JET L-mode plasmas

et al. 2019

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“…The significant suppression of Ion Temperature Gradient (ITG) dominated plasma turbulence via electromagnetic fluctuations and fast ions [1,2], for instance, has opened up the scope of turbulence reduction by alternative mechanisms to the wellknown E×B shearing. Such effects have also been shown to play an important role in the so-called isotope effect [3,4] and the recently found E×B staircase phenomenon [5][6][7].…”

Section: Introductionmentioning

confidence: 93%

A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E × B shearing

García

Doerk

Görler

et al. 2019

Plasma Phys. Control. Fusion

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Developing successful tokamak operation scenarios, as well as confident extrapolation of presentday knowledge requires a rigorous understanding of plasma turbulence, which largely determines the quality of the confinement. In particular, accurate particle transport predictions are essential due to the strong dependence of fusion power or bootstrap current on the particle density details. Here, gyrokinetic turbulence simulations are performed with physics inputs taken from a JET power scan, for which a relatively weak degradation of energy confinement and a significant density peaking is obtained with increasing input power. This way physics parameters that lead to such increase in the density peaking shall be elucidated. While well-known candidates, such as the collisionality, previously found in other studies are also recovered in this study, it is furthermore found that edge E×B shearing may adopt a crucial role by enhancing the inward pinch. These results may indicate that a plasma with rotational shear could develop a stronger density peaking as compared to a non-rotating one, because its inward convection is increased compared to the outward diffusive particle flux as long as this rotation has a significant on E×B flow shear stabilisation. The possibly significant implications for future devices, which will exhibit much less torque compared to present day experiments, are discussed.

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“…The power, torque and particle sources by NBH depend on both beam ion isotopes and hence also on the background plasma, as the general preference is to use the same species for NBH as for the main plasma. This warning can be extended to a comparison of D and DT plasmas, as the latter, unlike the former, will produce alpha particles which are potentially capable of reducing ITG turbulence by electromagnetic effects (Garcia, Görler & Jenko 2018).…”

Section: Effects Depending On Working Gas Isotopementioning

confidence: 99%

“…Such a deviation from gyroBohm scaling is enhanced in plasma conditions of high beta and high E × B shearing, as expected in advanced tokamak scenarios with high NBH power. In the particular case of DD vs DT plasmas, the additional fast ion contribution from the alpha particles from DT reactions can further reduce the ion heat flux by fast ion electromagnetic stabilisation resulting in considerable de-stiffening of the ITG mode, typically halving the ion heat flux for a given ion temperature gradient length (Garcia et al 2018). The higher fast ion pressure in deuterium plasmas heated by energetic ions has led to improved core confinement in a set of L-mode experiments in JET, with 3 He minority ion cyclotron resonance heating (ICRH) in addition to NBH (Bonanomi et al 2019b).…”

Section: Introductionmentioning

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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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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Isotope and fast ions turbulence suppression effects: Consequences for high-β ITER plasmas

Cited by 50 publications

References 23 publications

Role of fast ion pressure in the isotope effect in JET L-mode plasmas

Role of fast ion pressure in the isotope effect in JET L-mode plasmas

A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E × B shearing

Isotope dependence of energy, momentum and particle confinement in tokamaks

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