Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas

Bonofiglo, P. J.; Podestà, M.; Vallar, M.; Gorelenkov, N. N.; Kiptily, V.; White, R. B.; Giroud, C.; Brezinsek, S.

doi:10.1088/1741-4326/ac888c

Cited by 5 publications

(3 citation statements)

References 35 publications

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“…The slight increase in neutron emission during 1150 ms and 1300 ms might benefit from the reduction in magnetic perturbation amplitude. A prominent continuous decrease in neutron emission is observed during LLM phase inserted with several sawtooth crashes, which was also observed in JET [37].…”

Section: Resultssupporting

confidence: 66%

“…Additional magnetic perturbation is introduced to induce anomalous energetic ion losses when MHD instabilities are exited. Since LLM is excited around q ∼ 1 surface [37] which is shown by the yellow dash circles in figure 12, the energetic ions in the plasma core region are expected to be expelled to the peripheral region via convection as shown by the white arrows in figure 12. For the first component (see figure 12(a)), the lost energetic ions expelled from the plasma core to the peripheral region on the low field side (see the white arrows) have no chance to encounter lost particle orbits.…”

Section: Analysis For Energetic Ion Loss Processmentioning

confidence: 99%

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Investigation of energetic ion losses induced by long-lived saturated internal mode with energetic particle diagnostics in the HL-2A tokamak

Zhang,

Chen

et al. 2023

Nucl. Fusion

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Several sets of energetic particle diagnostics, including a set of neutron flux monitoring system, a solid-state neutral particle analyzer and a fast ion loss probe, have been used to investigate the energetic ion losses induced by the long-lived saturated internal mode (LLM) in the HL-2A tokamak. Clear experimental evidences for different levels of energetic ion losses induced by LLM, sawtooth and minor disruption have been observed. A numerical calculation for the evolution of neutron emissions was carried out with the FBURN code, and it shows that the neutron emission drop rate linearly increases with the LLM amplitude and no threshold perturbation amplitude exists, illustrating that the loss mechanism for LLM induced energetic ion loss is dominantly convective. In addition, measurement results of the fast ion loss probe demonstrate that LLM tends to expel energetic ions with relatively low energy (E < 27 keV) and high pitch angle (Θ>60°), and can suppress the prompt loss of energetic ions with high energy and low pitch angle to a certain degree. Furthermore, the physical process for LLM induced energetic ion loss can be explained by orbit calculations, which show that LLM induced lost energetic ions will transport from center to peripheral region first, and then get lost out of plasma. The experimental observations are successfully reproduced by calculations using the ORBIT code combined with both the NUBEAM code and the MARS-K code. The paper clearly describes the whole physical process of LLM induced energetic ion loss for the first time in the HL-2A tokamak.

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Section: Resultssupporting

confidence: 66%

Section: Analysis For Energetic Ion Loss Processmentioning

confidence: 99%

Investigation of energetic ion losses induced by long-lived saturated internal mode with energetic particle diagnostics in the HL-2A tokamak

Zhang,

Chen

et al. 2023

Nucl. Fusion

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show abstract

“…On the applied modeling side, there has been recent work on computationally efficient reduced fast ion transport models that took into account mechanisms responsible for energy-and pitch-selectivity of a sawtooth crash in order to improve the quantitative agreement with experimental measurements [17][18][19][20][21][22]. The methods proposed in the present paper may also be utilized in such efforts.…”

Section: Summary and Discussionmentioning

confidence: 99%

Time-helicity de-resonation (T-H) diagram for energy-selective mixing of charged particles during sawtooth crashes in tokamaks

Bierwage,

Lauber,

Shinohara

2024

Plasma Phys. Control. Fusion

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It was recently shown that there exists a narrow parameter window where benign sawtooth crashes cause only mixing of bulk plasma and slowed-down alpha particle "ash", while leaving MeV-class fast alphas largely unperturbed [Bierwage et al. Nat. Commun. 13 (2022) 3941]. Here, we revisit the underlying physical picture and reframe it in a manner that may be suitable for systematic analyses of this phenomenon in modeling, simulation and experimental studies. In particular, we propose a graph that we call "time-helicity de-resonation diagram" (short: T-H diagram) that captures the physical essence of energy-selectivity of sawtooth-particle interactions and visualizes it in a compact, intuitive way. Moreover, the regimes of good confinement and strong mixing during a sawtooth crash can be discerned via a single figure of merit: the T-H radius. The concept is introduced here on the basis of simulation results and would eventually benefit from further validation when applied to suitable empirical data.

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Loss of energetic ions due to n = 1 internal kink instability in HL-2M

et al. 2023

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Effects of three-dimensional (3D) perturbations due to an unstable n = 1 (n is the toroidal mode number) internal kink (IK) on the energetic particles (EPs) are systematically investigated for the HL-2M tokamak, utilizing the MARS-F/K code [Liu et al., Phys. Plasmas 7, 3681–3690 (2000)] and a recently developed test particle tracing module. A high-beta sawteething HL-2M scenario, simulated by the TRANSP code [Breslau et al., Transp Computer Software (2018)], is chosen for this study. In general, the 3D perturbation associated with an unstable IK is found to affect the EP drift orbit, confinement, and loss in HL-2M. The instability-induced EP loss fraction is found to be typically less than 10%, without counting for the prompt orbit loss associated with the 2D equilibrium field for counter-current particles. The latter reaches about 16% in HL-2M. For co-current EPs, a 100 G 3D magnetic field (inside the plasma) due to the IK does not induce any EP loss assuming a static perturbation. A sawtooth-like time-varying perturbation field, with the peak amplitude reaching 1000 G, can however produce about 30% loss for the co-current EPs in HL-2M. The majority of lost EPs tend to strike the lower divertor region, with a small fraction of particles striking the low-field side mid-plane region of the limiting surface.

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Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas

Cited by 5 publications

References 35 publications

Investigation of energetic ion losses induced by long-lived saturated internal mode with energetic particle diagnostics in the HL-2A tokamak

Investigation of energetic ion losses induced by long-lived saturated internal mode with energetic particle diagnostics in the HL-2A tokamak

Time-helicity de-resonation (T-H) diagram for energy-selective mixing of charged particles during sawtooth crashes in tokamaks

Loss of energetic ions due to n = 1 internal kink instability in HL-2M

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