MHD Instabilities in Current Carrying Heliotron Plasmas

Yamada, Goshi; Nakamura, Yuji; Kondo, K.

doi:10.1585/pfr.5.021

Cited by 2 publications

(2 citation statements)

References 10 publications

(11 reference statements)

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“…Although studies dedicated to the impact of MHD instabilities on the impurity behaviour are not considered to be part of this review paper, given their importance, a short mention is certainly in order. Close to the magnetic axis the effect of sawtooth profile relaxations in mitigating or even avoiding impurity accumulation has received large consideration [198,[213][214][215][216][217][218]. More recently, also more complicated effects have been identified and investigated, in which the presence of long-living, saturated internal kink modes at the q = 1 surface can produce helical deformations of the magnetic equilibrium which can affect the impurity transport, particularly through an interplay with central ECRH, leading to centrally hollow impurity density profiles [219,220].…”

Section: Review Of Theory-based Modelling Of Impurity Transport and I...mentioning

confidence: 99%

Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments

Angioni

2021

Plasma Phys. Control. Fusion

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In this paper, the theory of collisional and turbulent transport of impurities in tokamak plasmas is reviewed. The results are presented with the aim of providing at the same time a historical reconstruction of the scientific progress and a complete description of the present theoretical knowledge, with a hopefully sufficiently complete reference to the works which have been published in the field in the last decades. After a general introduction on the physics challenges offered by the problem of impurity transport and their relevance for practical nuclear fusion energy, the theory of collisional transport is presented. Here a specific section is also dedicated to the transport parallel to the magnetic field lines. A complete review of the transport mechanisms produced by turbulence follows. The corresponding comparisons between theoretical predictions and experimental observations are also presented, highlighting the influence that the validation activities had in motivating further theoretical investigations. The paper is completed by a section on the direct interactions between collisional and turbulent transport and by a final specific review dedicated to the progress in the theory–based modelling activities. In the writing of this review paper, the main goal has been to combine readability with completeness and scientific rigour, providing a comprehensive list of references for deeper documentation on specific aspects.

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Section: Review Of Theory-based Modelling Of Impurity Transport and I...mentioning

confidence: 99%

Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments

Angioni

2021

Plasma Phys. Control. Fusion

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“…To resolve this problem as well as potentially reduce tokamak cost [4], several non-inductive startup and current drive (CD) techniques are being developed. Solutions developed to date include local helicity injection [5], coaxial helicity injection (CHI) [6], plasma merging [7], and radio frequency (RF) wave injection [8]. Methods in which RF waves are used to produce a non-inductive current drive can be categorized into electron cyclotron CD (ECCD) [9], lower hybrid CD [10], and electron Bernstein wave current drive (EBWCD) [11].…”

Section: Introductionmentioning

confidence: 99%

Electron Bernstein wave conversion of high-field side injected X-modes in QUEST

Elserafy

Hanada

Kojima

et al. 2020

Plasma Phys. Control. Fusion

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This paper presents a detailed design of the Q-shu University experimental steady state spherical tokamak's (QUEST's) high-field side (HFS) injection system for electron Bernstein wave (EBW) excitation and the results of an experimental comparison of the HFS eXtraordinary X-mode and low-field side (LFS) ordinary O-mode injection of 8.2 GHz radio frequency (RF) power. Waveguides, as an alternative to mirror polarizers for transmitting RF X-mode power from LFS to HFS for EBW conversion, were used instead of the installation of an RF mirror. Testing of LFS-to-HFS RF power transmission at 8.2 GHz, using an RG-50-type vacuum waveguide in a bench-scale device filled with SF 6 gas at 0.03 Mpa, revealed that an RF power of 10.8 kW could traverse the fundamental electron cyclotron resonance layer for 60 s without breakdown. The short-length, open-ended waveguide antenna used in the HFS injection-induced wave diffraction reduced the efficiency of power delivery to the upper hybrid resonance (UHR) by approximately 7% at an electron temperature of 50 eV. The HFS injection was able to produce brighter camera images than the standard LFS injection. The location of the UHR, as estimated by measuring the density with an interferometer, agreed with its location as measured by plasma radiation low-field, side-edge positions shown by fast camera imaging. This indicates that the plasma was produced by modeconverted EBW. The HFS injection had an absorption efficiency of 96%, compared to 40% for LFS. A greater fluctuation of floating potential adjustable to the lower hybrid wave (LHW) was observed in the HFS case by installing a Langmuir probe, confirming that EBW conversion efficiency was higher in the HFS case. Moreover, after setting the poloidal field to B PF =7.6 mT, plasma current (I P ) in the HFS peaked at 1.3 kA, as opposed to 0.3 kA for LFS, despite LFS injection having a total power of 55 kW, compared to 40 kW for HFS. However, as the impurity level was comparatively high, it is believed that this I P is dominated by pressure-drive, which makes it difficult to analyze EBWCD. Finally, the line-integrated density in the HFS injection peaked at 1.6×10 18 m −2 , compared to 8×10 17 m −2 in the LFS one.

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MHD Instabilities in Current Carrying Heliotron Plasmas

Cited by 2 publications

References 10 publications

Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments

Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments

Electron Bernstein wave conversion of high-field side injected X-modes in QUEST

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