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

Bonanomi, N.; Casiraghi, I.; Mantica, P.; Challis, C.; Delabie, E.; Fable, E.; Gallart, D.; Giroud, C.; Lerche, E.; Lomas, P. J.; Menmuir, S.; Staebler, G. M.; Taylor, D.; Eester, D. Van; Contributors, Jet

doi:10.1088/1741-4326/ab2d4f

Cited by 24 publications

(51 citation statements)

References 48 publications

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“…Modelling of transport in the edge plasma and pedestal is still in its infancy, but deserves particular attention, as it sets the boundary conditions and via profile stiffness influences and often largely determines global confinement (Bateman et al 1999). Strong ion mass effects have been obtained in electromagnetic gyrokinetic GENE simulations of L-mode edges in AUG and JET (Bonanomi et al 2019b). The results show that edge turbulence is radically distinct from core turbulence.…”

Section: Introductionmentioning

confidence: 90%

“…Due to the steep gradients, electromagnetic effects are also important despite the relatively low local thermal β. MHD-like electron drift waves are strongly destabilised even at low (with respect to core values) values of β e . This destabilisation especially affects modes with low wave numbers and is found to take place below the threshold in β e expected from linear simulations (Bonanomi et al 2019b). This behaviour puts into question the applicability in the edge plasma of the conventional approach of developing quasilinear models for describing transport.…”

Section: Introductionmentioning

confidence: 94%

“…The analysis shows that plasma density profiles in the boundary are governed also by particle transport processes and are more complex than expected from neutral fuelling physics only. We expect better insights into the nature of transport in the H-mode pedestal and its dependence on the isotope species from gyrokinetic modelling (like the one in Bonanomi et al 2019b, for the L-mode edge) in conjunction with the application of MHD stability constraints.…”

Section: Particle Transport In the H-mode Pedestalmentioning

confidence: 99%

“…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. 2019 b ). It is important to stress that a different fast ion contribution in different plasma species is not an inherent isotope effect.…”

Section: Effects Depending On Working Gas Isotopementioning

confidence: 99%

“…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). It is important to stress that a different fast ion contribution in different plasma species is not an inherent isotope effect.…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 94%

Section: Particle Transport In the H-mode Pedestalmentioning

confidence: 99%

Section: Effects Depending On Working Gas Isotopementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Isotope dependence of energy, momentum and particle confinement in tokamaks

Weisen

Maggi²,

Oberparleiter³

et al. 2020

J. Plasma Phys.

Self Cite

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Effects of the energetic particles on the anomalous transport driven by the ion temperature gradient instability

et al. 2022

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When the charge exchange time ( τcx) is sufficiently shorter than the slowing-down time ( τsl), the distribution of energetic particles (EPs) is bump-on-tail. In this work, the effects of EPs on the anomalous transport driven by the ion temperature gradient (ITG) instability are investigated. The dispersion relation is theoretically derived and numerically solved to analyze the effects of EPs on the linear frequency of ITG instability. Two kinds of bump-on-tail distribution, denoted by [Formula: see text] and 6.8, and the slowing-down distribution, denoted by τ = 0, are considered. Based on the linear results, the quasilinear particle and energy fluxes of bulk ions are analyzed. It is found that effects of the EPs on the ITG linear frequency and quasilinear transport are obvious in the regions with the EPs initial energy [Formula: see text] and the EPs charge concentration [Formula: see text], where Te is the electron temperature, Zh and [Formula: see text] are the charge number and fraction of EPs, respectively. Existence of the EPs is beneficial for the stabilization of ITG instability. Moreover, the ITG instability can be better stabilized with the bump-on-tail distribution of energetic deuterium (D) and the slowing-down distribution of energetic helium (He). However, in the cases with the slowing-down distribution of D and the bump-on-tail distribution of He, the particle fluxes of bulk ions are inwardly largest and the energy fluxes of bulk ions are outwardly smallest, which indicate that the better particle and energy confinement appear with the slowing-down distribution of D and the bump-on-tail distribution of He.

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Interpretative and predictive modelling of Joint European Torus collisionality scans

Eriksson

Fransson

Oberparleiter

et al. 2019

Plasma Phys. Control. Fusion

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Transport modelling of Joint European Torus (JET) dimensionless collisionality scaling experiments in various operational scenarios is presented. Interpretative simulations at a fixed radial position are combined with predictive JETTO simulations of temperatures and densities, using the TGLF transport model. The model includes electromagnetic effects and collisions as well as E ⃗ × B ⃗ shear in Miller geometry. Focus is on particle transport and the role of the neutral beam injection (NBI) particle source for the density peaking. The experimental 3-point collisionality scans include L-mode, and H-mode (D and H and higher beta D plasma) plasmas in a total of 12 discharges. Experimental results presented in (Tala et al 2017 44th EPS Conf.) indicate that for the H-mode scans, the NBI particle source plays an important role for the density peaking, whereas for the L-mode scan, the influence of the particle source is small. In general, both the interpretative and predictive transport simulations support the experimental conclusions on the role of the NBI particle source for the 12 JET discharges.

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

Cited by 24 publications

References 48 publications

Isotope dependence of energy, momentum and particle confinement in tokamaks

Isotope dependence of energy, momentum and particle confinement in tokamaks

Effects of the energetic particles on the anomalous transport driven by the ion temperature gradient instability

Interpretative and predictive modelling of Joint European Torus collisionality scans

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