Analysis of higher harmonics on bidirectional heat pulse propagation experiment in helical and tokamak plasmas

Kobayashi, Tatsuya; Ida, K.; Inagaki, S.; Takahashi, Hayato; Tamura, N.; Choe, G.H.; Yun, Gunsu; Park, H.K.; Ko, W. H.; Evans, T.E.; Austin, M. E.; Shafer, Morgan; Ono, Makoto; López‐Bruna, D.; Ochando, M. A.; Estrada, T.; Hidalgo, C.; Moon, Chanho; Igami, H.; Yoshimura, Y.; Tsujimura, Toru Ii; Itoh, Sanae I.; Itoh, K.

doi:10.1088/1741-4326/aa6f1f

Cited by 10 publications

(17 citation statements)

References 21 publications

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“…However, if the slopes are compared to the profiles belonging to the redistributed or wide profile (dashed lines) one sees directly that they are no longer straight and are lifted up for the amplitude and increase much slower for the phase. Exactly this effect has been observed in several machines [17,43,44], where the latter two references also suggest it could be due to hysteresis. This confirms that this effect is not limited to stellarators.…”

Section: Frequency Domain: Effect On the Estimated Transport Coeffici...mentioning

confidence: 76%

Separation of transport in slow and fast time-scales using modulated heat pulse experiments (hysteresis in flux explained)

et al. 2018

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Old and recent experiments show that there is a direct response to the heating power of transport observed in modulated ECH experiments both in tokamaks and stellarators. This is most apparent for modulated experiments in the Large Helical Device (LHD) and in Wendelstein 7 advanced stellarator (W7-AS). In this paper we show that: (1) this power dependence can be reproduced by linear models and as such hysteresis (in flux) has no relationship to hysteresis as defined in the literature; (2) observations of ‘hysteresis’ (in flux) and a direct response to power can be perfectly reproduced by introducing an error in the estimated deposition profile as long as the errors redistribute the heat over a large radius; (3) non-local models depending directly on the heating power can also explain the experimentally observed Lissajous curves (hysteresis); (4) how non-locality and deposition errors can be recognized in experiments and how they affect estimates of transport coefficients; (5) from a linear perturbation transport experiment, it is not possible to discern deposition errors from non-local fast transport components (mathematically equivalent). However, when studied over different operating points non-linear-non-local transport models can be derived which should be distinguishable from errors in the deposition profile. To show all this, transport needs to be analyzed by separating the transport in a slow (diffusive) time-scale and a fast (heating/non-local) time-scale, which can only be done in the presence of perturbations.

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Section: Frequency Domain: Effect On the Estimated Transport Coeffici...mentioning

confidence: 76%

Separation of transport in slow and fast time-scales using modulated heat pulse experiments (hysteresis in flux explained)

et al. 2018

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“…so-called non-local transport problems) [2]. For example, the following observations have been reported: the spontaneous rise of core temperature by edge cooling [3][4][5], the rapid and ballistic response of transport fluxes [6,7] and hysteresis in the flux-gradient relations, which is not explained by the local parameters [8,9].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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Turbulent transport is undoubtedly important in magnetic confinement plasmas. It has been reported that a lot of transport dynamics are not satisfying the local diffusive models. Here, we report the quantitative measurement of electron heat flux associated with ballistic propagating long-ranged transport events, which is considered as a component of avalanches. In addition, we show the first observations of substantial impact of avalanche-driven transport on profile resilience (or profile stiffness) observed in JT-60U. We found that, in the channel of the electron heat flux, the ratio between the increment of avalanche-driven component to that of the total plasma heating becomes dominant (~80%) in the case of high-heating limit. This suggests a possible role of avalanche-driven transport to induce the profile resilience, which have been claimed by the flux-driven simulations.

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“…An advantage of this model is that the transport can be expressed only by two scalar coefficients, i.e., the diffusivity and the convective velocity. However, if the assumed model is improper in accounting for the actual plasma transport, obtained results immediately mislead us in interpreting the plasma thermal confinement [28,29,30]. To prevent overlooking phenomena outside the assumed model, we prefer to directly observe the flux-gradient relation.…”

Section: A Brief Review Of Transport Hysteresismentioning

confidence: 99%

“…Radial profiles of the electron density and the electron temperature for the representative discharges for the D, H, and mixed plasmas at the line averaged density of ∼ 1. where the ECH deposition is absent in the conventional local point of view. Note that the local thermal transport coefficients are shown to be insufficient to fully express the electron heat pulse propagation in LHD [28,30].…”

Section: Electron Heat Pulse Transportmentioning

confidence: 99%

“…In particular, under a modulation ECH (MECH) application, the trajectory in the flux-gradient diagram draws a loop, which we call the transport hysteresis. When the transport hysteresis emerges, a single scalar transport coefficient is found to be no longer valid for representing the transport property of the high temperature plasmas [28][29][30][31]. A theoretical model predicts that the magnitude of the hysteresis is more enhanced in lighter isotope mass plasmas, which results in the confinement degradation and therefore explains the isotope effect [27].…”

Section: Isotope Effect In Transient Electron Thermal Transport Prope...mentioning

confidence: 99%

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Isotope effect in transient electron thermal transport property and its impact on the electron internal transport barrier formation in LHD

et al. 2020

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In this study, we perform a comprehensive comparison of the transport hysteresis width in deuterium (D) plasmas, hydrogen (H) plasmas, and D-H mixed plasmas. The core focused modulation electron cyclotron resonance heating (MECH) is applied as the heat source perturbation, and the heat flux is evaluated using the energy conservation equation with the measured electron temperature response and the ECH deposition profile calculated by the raytracing scheme. Systematic density scan in plasmas with different ion mass reveals that there is no significant isotope effect in their hysteresis width. It is found that plasmas with heavier isotope mass can easily form the electron internal transport barrier. As the hysteresis width is insensitive to the isotope mass, the classical part of the diffusivity is considered to be responsible for the isotope effect in the transport barrier formation.

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Analysis of higher harmonics on bidirectional heat pulse propagation experiment in helical and tokamak plasmas

Cited by 10 publications

References 21 publications

Separation of transport in slow and fast time-scales using modulated heat pulse experiments (hysteresis in flux explained)

Separation of transport in slow and fast time-scales using modulated heat pulse experiments (hysteresis in flux explained)

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

Isotope effect in transient electron thermal transport property and its impact on the electron internal transport barrier formation in LHD

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