Isotope effect on zonal flow and its configuration dependence in low-density electron-cyclotron-resonance heated plasmas in Heliotron J

Ohshima, S.; Okada, H.; Zang, L.; Kobayashi, S.; Minami, Takashi; Kado, S.; Adulsiriswad, Panith; Qiu, D.; Matoike, R.; Luo, M.; Zhang, P.; Miyashita, A.; Motoshima, M.; Nakamura, Yusuke; Konoshima, S.; Mizuuchi, T.; Nagasaki, K.

doi:10.1088/1361-6587/ac1837

Cited by 5 publications

(4 citation statements)

References 52 publications

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“…The isotope effect has also been suggested to interpret the low power threshold required for L-H transition in D plasmas compared to H plasmas at lowdensity discharges in DIII-D [20]. Recently, the experimental results in Heliotron J indicated that the zonal flow (<4 kHz) is dependent on the isotope mass in the standard magnetic configuration, whereas no zonal flow activity was observed in the low bumpiness configuration [21]. On the other hand, the experimental observation in TJ-II showed that the amplitude of the long-range correlation decreases slightly with increasing isotope mass in electron cyclotron resonance heated (ECRH) plasmas [22] and no isotope effect was observed in the L-H transition [23,24].…”

Section: Introductionmentioning

confidence: 99%

Isotope effects on turbulence and zonal flows in HL-2A edge plasmas

He¹,

Cheng²,

Xu³

et al. 2022

Nucl. Fusion

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The effect of isotope mass on the interaction between turbulence and geodesic acoustic mode (GAM) zonal flows has been investigated in HL-2A ohmically heated deuterium (D) and hydrogen (H) plasmas using a double-step Langmuir probe array. The experimental results indicate that the level of GAM zonal flows and the turbulence eddy size together with the eddy tilting angle are all increased in the edge region in D plasmas compared to those in H plasmas under similar discharge parameters involving plasma current, magnetic field and line-averaged density. Evidence shows that in D plasmas, the nonlinear energy transfer is the main cause of the stronger excitation of GAM zonal flows, which extract more energy from ambient turbulence and, consequently, lead to lower turbulent transport and better confinement in D plasmas. The experimental findings may contribute to the understanding of the isotopic physics and associated turbulent transport in tokamak plasmas.

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Section: Introductionmentioning

confidence: 99%

Isotope effects on turbulence and zonal flows in HL-2A edge plasmas

He¹,

Cheng²,

Xu³

et al. 2022

Nucl. Fusion

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show abstract

“…It is used in worldwide fusion devices such as tokamaks (ASDEX Upgrade [1,2], DIII-D [3], JT-60U [4]) and stellarator/heliotron (Wendelstein 7-AS [5], Wendelstein 7-X [6], TJ-II [7], LHD [8], Heliotron J [9,10]) and has great contributions to the measurement of turbulence and E r on plasma dynamics such as L-H transition. In Heliotron J, Langmuir probes have been used to search for ZF [11], and in this study, a dual Doppler reflectometry system is newly introduced to extend the parameter and operation space for turbulence and ZF studies. An O-mode Doppler reflectometry system has been operated for poloidal flow and radial electric field measurements since 2019 [9].…”

Section: Jinst 17 C05023mentioning

confidence: 99%

Development of dual X-mode Doppler reflectometry system in Heliotron J

et al. 2022

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A dual X-mode Doppler reflectometry system is developed to measure the radial electric field in a stellarator/heliotron device, Heliotron J. The system is designed to have dual channels where the observation points are placed symmetrically to the equatorial plane, enabling the poloidal flow velocity measurement at two different positions in the same toroidal section, which is useful for the search for a zonal flow. In the system, an RF source generates the microwave frequency of 8.25–12.5 GHz, upconverted by an intermediate frequency of 27.5 MHz and transmitted with a coaxial cable to a transmitter located near the Heliotoron J vacuum vessel. After quadrupling the RF waves at the transmitter, the microwaves of 33–50 GHz are injected in X-mode into a plasma using a spherical focusing mirror installed inside the vacuum vessel. The local wavenumber of the probing microwaves, k ⊥, is 1.56–1.66 cm−1. The Doppler-shifted reflected wave is downconverted to a 110 MHz signal by mixing with the LO at the receiver, amplified, and then detected by an I/Q detector. In a tabletop test, we have confirmed that the phase estimated by the I/Q detector is proportionally changed as a function of the horn antenna distance. We have successfully measured the Doppler-shifted spectra of the I/Q signals and estimated the radial electric field in an electron cyclotron heated (ECH) plasma.

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“…On the other hand, the importance of multiscale physics, such as turbulence and zonal flows, in isotope effects have been identified experimentally in tokamaks and stellarators [2,6,[16][17][18][19][20][21][22][23][24]. Experimental results revealed that transport properties and turbulence modes, e.g.…”

Section: Introductionmentioning

confidence: 99%

Isotope effects on transport characteristics of edge and core plasmas heated by neutral beam injection (NBI) in an inward shifted configuration at the Large Helical Device

Zhou,

Xu,

Kobayashi

et al. 2024

Nucl. Fusion

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Isotope effects have been investigated in neutral beam injection (NBI) heated plasmas on the Large Helical Device (LHD) with similar operational parameters between hydrogen (H) and deuterium (D) plasmas. Experimental results show that the global energy confinement has no significant dependence on the isotope mass under similar discharge conditions with nearly the same heating power, line-averaged density (n ̅_e) and magnetic field. For both electron and ion energy transport, the transport coefficients, which are obtained based on local power balance analysis, have analogous profiles between H and D dominant plasmas. For neoclassical χ_e and χ_i values, they are almost equal between H and D dominant plasmas in low n ̅_e discharges, whereas in high n ̅_e cases they are lower in H plasmas than those in D ones. At low n ̅_e, the electron and ion thermal transport in both H and D plasmas are dominated by neoclassical transport at a certain zone (ρ≈0.6-0.85), while the anomalous transport process has primary effects in the remaining area, and the density fluctuations exhibit ion temperature gradient mode nature. With increase of n ̅_e, the anomalous transport becomes prevailing and the density fluctuations propagate along electron diamagnetic drift direction. Bispectral analysis reveals that the H plasma has stronger nonlinear coupling in edge density fluctuations in both low and high density discharges, which is probably due to that the D plasma has stronger damping rate for the nonlinear interaction of turbulence. For a comparative study, the present results have been compared with those observed in the ECRH discharges [1]. The reasons for the similarities and dissimilarities between these two different heating manners are not clear yet. To unravel the underlying physics, essential inputs from theories and simulations are required.

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Isotope effect on zonal flow and its configuration dependence in low-density electron-cyclotron-resonance heated plasmas in Heliotron J

Cited by 5 publications

References 52 publications

Isotope effects on turbulence and zonal flows in HL-2A edge plasmas

Isotope effects on turbulence and zonal flows in HL-2A edge plasmas

Development of dual X-mode Doppler reflectometry system in Heliotron J

Isotope effects on transport characteristics of edge and core plasmas heated by neutral beam injection (NBI) in an inward shifted configuration at the Large Helical Device

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