Spectroscopic study of impurities in neutral beam heated and ohmically heated JT-60 discharges

Kubo, H.; Sugie, Toshiharu; Sakasai, A.; Koide, Y.; Nishino, Norikazu; Hirayama, T.; Nishitani, T.; Nagashima, Keisuke; Akaoka, N.; Takeuchi, Hiroshi; Team, Jt

doi:10.1088/0029-5515/29/4/003

Cited by 10 publications

(6 citation statements)

References 18 publications

(30 reference statements)

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“…In this paper, the positive sign and the negative sign of the toroidal rotation velocity indicate the co-direction and the ctr-direction, respectively. The effective ion charge Z eff is estimated with the measurement of Bremsstrahlung [33]. The radiation power is obtained with the bolometer [34].…”

Section: Heating System and Diagnostic Of Jt-60umentioning

confidence: 99%

Effect of m/n = 2/1 neoclassical tearing mode on sawtooth collapse in JT-60U

Bando¹,

Wakatsuki²,

Honda³

et al. 2021

Plasma Phys. Control. Fusion

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We have investigated the role of the m/n = 2/1 neoclassical tearing mode (NTM) for suppression of the sawtooth collapse in JT-60U from the viewpoint of the anomalous transport of the current diffusion, namely flux pumping. In the stabilization experiments of m/n = 2/1 NTMs by electron cyclotron current drive of JT-60U, it has been clarified that the sawtooth collapses occur during or after the stabilization of m/n = 2/1 NTMs. It is also confirmed that the minimum safety factor, q min , is nearly unity before and after the stabilization of an m/n = 2/1 NTM. While the flux pumping by ELM-NTM coupling was reported in DIII-D, the suppression of the sawtooth collapse is observed without ELMs in this study. On the other hand, it is observed that the sawtooth precursor appears during the stabilization of the m/n = 2/1 NTM accompanying the disappearance of the fluctuation of the n = 1 helical core (HC), which is induced by the m/n = 2/1 NTM. In addition, the modulation of the toroidal rotation velocity having the frequency of the n = 1 HC is observed in the core region. Because the helical flow with HCs is a possible source of the dynamo loop voltage in tokamaks, these observations suggest that the suppression of the sawtooth collapse in JT-60U is realized by the dynamo loop voltage due to the n = 1 HC induced by the m/n = 2/1 NTM. Our result indicates that n = 1 HCs induced by other MHD modes also may induce anomalous current transport in tokamaks.

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Section: Heating System and Diagnostic Of Jt-60umentioning

confidence: 99%

Effect of m/n = 2/1 neoclassical tearing mode on sawtooth collapse in JT-60U

Bando¹,

Wakatsuki²,

Honda³

et al. 2021

Plasma Phys. Control. Fusion

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“…After the transition, the radiation loss from the divertor tends to increase by a factor of two above that in the L-mode phase, just before the transition. The concentration ratios of these impurities are 2% for oxygen, 0.4% for carbon and (0.5-2) x 10" 3 % for titanium at h^ = 4 x 10 l 9 nr 3 [37].…”

Section: Radiation Loss and Impuritymentioning

confidence: 95%

H-mode experiments with outer and lower divertors in JT-60

et al. 1990

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In JT-60, H-mode experiments with outer and lower divertors have been performed. In the outer divertor discharge, an H-mode similar to the modes observed in the lower/upper divertor discharges is obtained. Its threshold absorbed power and electron density are 16 MW and 1.8 × 1019 m−3. In the two schemes of combined heating with NB + ICRF and NB + LHRF, H-mode discharges are also obtained. Moreover, in the new configuration with the JT-60 lower divertor, H-mode phases with and without edge localized modes are obtained. The improvement in the energy confinement time in both divertor configurations is limited to values within 10%. The paper mainly presents the H-mode results of the outer divertor discharges. Also, typical results of the lower divertor discharges are shown for a comparison of the H-mode characteristics of the two configurations.

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“…Our interest of such a spectral line is because the vacuum vessel of HL-2A tokamak is covered by a large area of carbon tiles. In particular, CXR can play an important role in determining the ionization balance when large densities of neutral deuterium atoms are present, such as during neutral beam injection (NBI) for plasma heating or at the plasma edge where the density of thermal neutral atoms can be significant [29][30][31]. Measurements of the CXR is based on charge transfer from high energy neutral deuterium atoms to fully stripped carbon ions.…”

Section: Reconstruction Of Line Radiationmentioning

confidence: 99%

Application of Bayesian tomography method to the visible spectroscopic diagnostic on HL-2A tokamak

Liu¹,

Liu²,

Svensson

et al. 2021

Plasma Phys. Control. Fusion

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As the commission of a visible spectroscopic diagnostic to the HL-2A tokamak for the measurements of both bremsstrahlung continuum radiation and impurity line emission, a Bayesian tomography method has been developed to this diagnostic for the reconstruction of a 2D emission distribution from line-integrated data. In this method, Gaussian process prior is adopted as an effective way to regularize the smoothness of the emission field, which can be truncated to enforce non-negative constraint of the emission values. For the reliability and quality assessment, uncertainty of the reconstruction can be examined through its confidence interval derived from a posterior probability. Performance of this Gaussian process tomography method is exemplified by the reconstructions of the bremsstrahlung continuum emission, which coincide with the equilibrium magnetic flux surfaces with respect to position and shape. In another case the reconstruction of CVI line emission in the visible range (n = 8→7, 529.05 nm) disclose the existence of a bright radiation belt due to the plasma–wall interaction.

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Spectroscopic study of impurities in neutral beam heated and ohmically heated JT-60 discharges

Cited by 10 publications

References 18 publications

Effect of m/n = 2/1 neoclassical tearing mode on sawtooth collapse in JT-60U

Effect of m/n = 2/1 neoclassical tearing mode on sawtooth collapse in JT-60U

H-mode experiments with outer and lower divertors in JT-60

Application of Bayesian tomography method to the visible spectroscopic diagnostic on HL-2A tokamak

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