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

Nakamura, Hiroo; Tsuji, S.; Nagami, M.; Ozeki, T.; Ishida, S.; Azumi, M.; Akiba, Masato; Ando, T.; Fujii, T.; Fukuda, T.; Hirayama, Toshio; Hiroki, Seiji; Horiike, Hiroshi; Hosogane, N.; Ikeda, Yoshitaka; Imai, T.; Itami, K.; Kamada, Y.; Kikuchi, M.; Kimura, Hiroyuki; Kubo, H.; Kuriyama, M.; Matsuoka, M.; Miya, N.; Nagashima, Keisuke; Naito, O.; Ninomiya, H.; Nishitani, T.; Saigusa, M.; Satō, Masayasu; Shimizu, K.; Shirai, Hiroshi; Sugie, Toshiharu; Takeuchi, Hiroshi; Uehara, K.; Ushigusa, K.; Yoshida, H.; Yoshino, R.

doi:10.1088/0029-5515/30/2/004

Cited by 19 publications

(6 citation statements)

References 41 publications

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“…Respective roles of inner-wall limiter and X-point operation are important missing pieces of information. For the latter subject, it reminds us that the original JT-60 had divertor X-point in the outboard mid-plane and showed very short period of H-mode but returned to L-mode confinement [31]. Possible sustainment of L-mode edge in a reactor is further discussed in section 3.2.…”

Section: L-mode Edge Operationmentioning

confidence: 90%

L-mode-edge negative triangularity tokamak reactor

et al. 2019

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The negative triangularity tokamak (NTT) is a unique reactor concept based on "powerhandling-first" philosophy with the heat exhaust problem as the leading concern. The present paper exposes a reactor concept using L-mode edge based on negative triangularity tokamak (NTT) configuration, providing merits of no (or very weak) ELMs, larger particle flux and large major radius for power handling. It is shown that a reasonably compact (R p from 9m to 7m) NTT reactor is possible by achieving higher confinement improvement (H H =1.5) and/or by utilizing reasonably higher magnetic field (B max =15.5T). Current physics basis and critical issues on its scientific and technical feasibility are discussed. 1. PHYSICS BACKGROUND OF NTT REACTOR

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Section: L-mode Edge Operationmentioning

confidence: 90%

L-mode-edge negative triangularity tokamak reactor

et al. 2019

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“…When JT-60 installed its original divertor, it was localized on the low field side of the plasma [17,18]. The experiments with the outer divertor were able to produce short lived H-modes that improved the energy confinement time only by 10%.…”

Section: Earlier Experiments With a Bulge On The Bad Curvature Sidementioning

confidence: 99%

Ballooning instability preventing the H-mode access in plasmas with negative triangularity shape on the DIII–D tokamak

Saarelma¹,

Austin²,

Knölker³

et al. 2021

Plasma Phys. Control. Fusion

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Infinite toroidal mode number (n = ∞) ballooning mode analysis of negative triangularity discharges on DIII-D shows that the access to 2 nd stability becomes strongly restricted when the top triangularity decreases even modestly from −0.18 to −0.36. This is observed in experiment to coincide with the suppression of the L-H-transition. Further theoretical analysis with ballooning mode limited pedestals shows that the threshold for opening the 2 nd stability access rises from a pedestal temperature of 0.3-1 keV when the top triangularity is decreased from −0.18 to −0.36 indicating that to access the 2 nd stability with the more negative triangular shape would require unrealistically high pedestal temperature. The pedestal predicted by the EPED code agrees with the experimental H-mode profile for the negative triangularity case but in contrast to positive triangular shapes the prediction shows no increase in pedestal height with increasing core pressure when triangularity is negative. This work provides a first model to predict when negative triangularity plasmas can be expected to access the H-mode.

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“…This effect may account for the high heating power that is required in some tokamaks (e.g. ASDEX [19] and JT-60 [20]) to achieve the H-mode. Large toroidal asymmetries in the divertor heat flux of ASDEX [21] are an indication that error fields may play a role in its confinement.…”

Section: Discussionmentioning

confidence: 99%

Effects of applied error fields on the H-mode power threshold of JFT-2M

et al. 1991

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Applied error fields raise the H-mode power threshold, but do not significantly affect energy confinement in the JFT-2M tokamak. Magnetic perturbations of magnitude b̃n.m/BT ≈ (2-5) × 10−4 resonant near the plasma edge, raise the H-mode power threshold from 350 kW to 550 kW of neutral beam injection power. The global energy confinement is not affected once the H-mode is achieved. These measurements give an indication of the accuracy to which tokamak coils should be designed and maintained in order to ensure optimal access to the H-mode.

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

Cited by 19 publications

References 41 publications

L-mode-edge negative triangularity tokamak reactor

L-mode-edge negative triangularity tokamak reactor

Ballooning instability preventing the H-mode access in plasmas with negative triangularity shape on the DIII–D tokamak

Effects of applied error fields on the H-mode power threshold of JFT-2M

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