Experimental evaluation of avalanche type of electron heat transport in magnetic confinement plasmas

Kin, Fumiyoshi; Itoh, K.; Bando, T.; Shinohara, K.; Oyama, N.; Yoshida, M.; Kamiya, K.; Sumida, S.

doi:10.1088/1741-4326/aca341

Cited by 8 publications

(13 citation statements)

References 59 publications

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“…S av = height × width × length = δT × δR × 2π Rq. Note that it can be related to a heat flux carried by each avalanche, Q ∼ 3 2 nδTδv r [17] where δv r is the avalanche propagation speed, assuming that δR is associated with δv r . It can be further written that S av ∼ δTδR ∼ δTδv r ∼ δT 2 ∼ S with δv r ∼ δT [36].…”

Section: The Avalanche Pseudo-size Distributionmentioning

confidence: 99%

“…However, various self-organized structures have been reported in tokamak plasmas [5], and two of them, which coexist in the near-marginal regime, are avalanches and the E × B staircase. Avalanches [4,6] mean the ballistic flux propagation events through radially successive (non-local [7]) interactions [8][9][10][11][12][13][14][15][16][17]. They are named after the avalanche of the self-organized criticality (SOC) system [3,[18][19][20][21], because they are fast relaxation events of various sizes, exhibiting the power-law spectrum (long time correlation) and the large Hurst exponent [22].…”

Section: Introductionmentioning

confidence: 99%

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Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Choi,

Kwon,

et al. 2024

Plasma Phys. Control. Fusion

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The self-organization is one of the most interesting phenomena in the non-equilibrium complex system, generating ordered structures of different sizes and durations. In tokamak plasmas, various self-organized phenomena have been reported, and two of them, coexisting in the near-marginal (interaction dominant) regime, are avalanches and the E × B staircase. Avalanches mean the ballistic flux propagation event through successive interactions as it propagates, and the E × B staircase means a globally ordered pattern of self-organized zonal flow layers. Various models have been suggested to understand their characteristics and relation, but experimental researches have been mostly limited to the demonstration of their existence. Here we report detailed analyses of their dynamics and statistics and explain their relation. Avalanches influence the formation and the width distribution of the E × B staircase, while the E × B staircase confines avalanches within its mesoscopic width until dissipated or penetrated. Our perspective to consider them the self-organization phenomena enhances our fundamental understanding of them as well as links our findings with the self-organization of mesoscopic structures in various complex systems.

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Section: The Avalanche Pseudo-size Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Choi,

Kwon,

et al. 2024

Plasma Phys. Control. Fusion

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“…The boundary location of ρ ≈ 0.55 is approximately coincident with the peak of the electron temperature gradient, which is shown in figure 2(g). The simultaneous appearance of voids and bumps becomes significant with the heating power increase [17].…”

Section: Electron Heat Perturbations In Heliotron J and Jt-60umentioning

confidence: 99%

“…Therefore, avalanches can drive the longradial transport, which could demonstrate the non-local phenomena. The avalanches are considered to contribute to the global profile formation including the stiffness profile [15][16][17] to the submarginal profile [18,19]. Therefore, investigating the avalanches in both stellarator/heliotrons and tokamaks is important to understand the different transport features observed between the devices.…”

Section: Introductionmentioning

confidence: 99%

Observation of avalanche-like transport in Heliotron J and JT-60U plasmas

Kin,

Inagaki,

Nagasaki

et al. 2024

Nucl. Fusion

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The avalanche type of transport can induce a long-radial transport and thus can contribute to the global profile formation. In this study, we observed the heat perturbations exhibiting avalanche-like transport in the stellarator/heliotron device, Heliotron J, and the tokamak device, JT-60U. We found that the electron heat propagation in Heliotron J is mainly generated from the heating source region. The relatively high value of the Hurst exponent, which is a signature of avalanches, depends on the total heating power. On the other hand, the electron and ion heat avalanches measured in JT-60U tend to spread from the local peak of the temperature gradient and are not influenced by the heating source profiles. The contrasting features of avalanches in stellarator/heliotrons and tokamaks potentially imply the difference in the temperature profile formation, such as the presence of stiffness.

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“…Electron thermal transport is a fundamental process in diverse fields of plasma physics, including inertial confinement fusion (ICF), magnetic confinement fusion, and astrophysics [1][2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Space-time dependent non-local thermal transport effects on laser ablation dynamics in inertial confinement fusion

Yuan,

Zhao,

Zhu

et al. 2024

Plasma Phys. Control. Fusion

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In inertial conﬁnement fusion (ICF), electron thermal transport plays a key role in the laser ablation and subsequent implosion processes, which, however, always exhibits the intractable non-local eﬀect. Simple modiﬁcations of the local Spitzer-Härm model with either an artiﬁcially-assumed constant ﬂux limiter or a purely time-dependent one are applied to explain some experimental data, but fails to simultaneously reproduce the space-time evolution of the whole laser ablation process. Here, through carrying out a series of one-dimensional and two-dimensional radiation hydrodynamic simulations, where the space-time-dependent non-local thermal transport model proposed by Schurt, Nicolaı̈ and Busquet (the SNB model) are self-consistently included, we systematically study the non-local eﬀects on the whole laser ablation dynamics including those occurring at the critical surface, the conduction zone and the ablation front. Diﬀerent from those obtained previously, our results show that, because of the non-local heat ﬂow redistribution and redirection, at the critical surface the thermal ﬂux is more inhibited, in the conduction zone the lateral thermal transport is suppressed, and ahead of the ablation front the plasma is preheated, which, combined together, eventually result in signiﬁcant improvement of the laser absorption eﬃciency, extension of the conduction zone, increase of both the mass ablation rate and shock velocity. Furthermore, dependences of these laser ablation dynamics on diﬀerent drive laser intensities are investigated, which provides beneﬁcial enlightenments on potential laser pulse shaping and/or ignition scheme optimization in ICF.

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Experimental evaluation of avalanche type of electron heat transport in magnetic confinement plasmas

Cited by 8 publications

References 59 publications

Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Mesoscopic transport in KSTAR plasmas: avalanches and the E × B staircase

Observation of avalanche-like transport in Heliotron J and JT-60U plasmas

Space-time dependent non-local thermal transport effects on laser ablation dynamics in inertial confinement fusion

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