Development of high-power, long-pulse, multi-frequency ECH/CD system for JT-60SA

Kobayashi, Takayuki; Yamazaki, H.; Hiranai, S.; Sawahata, M.; Terakado, M.; Ishita, K.; Hinata, J.; Sato, Fumiaki; Wada, Kenji; Toida, Nobuhiro; Ikeda, Ryosuke; Shinya, Takahiro; Yajima, S.; Takahashi, Koji; Moriyama, S.

doi:10.1088/1741-4326/ac42f4

Cited by 7 publications

(4 citation statements)

References 33 publications

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“…The mechanisms for the formation of full RE discharges during plasma startup are investigated in section 4. In section 5, we review and discuss the operational conditions for successful plasma startup at JT-60SA and the strategies to apply prepared options, such as stray field optimisation [36] and electron cyclotron heating (ECH) [37], to expand the operational pressure range. The conclusions of this study are presented in section 6.…”

Section: Introductionmentioning

confidence: 99%

Modelling of ohmic startup and runaway electron formation in support of JT-60SA initial operation

Matsuyama¹,

Wakatsuki²,

Inoue³

et al. 2022

Nucl. Fusion

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The plasma startup with ITER-relevant sub-mPa neutral pressures in the JT-60SA superconducting tokamak is studied using a zero-dimensional (0D) power balance model for the plasma burn-through phase. In the ohmic startup scenario assumed here, the lower limit of the operational neutral pressure is determined by the condition for the Townsend avalanche at a high $E/p$ limit, whereas the upper limit depends on the available ohmic heating power for the burn-through with the base Power Supply (PS) of the superconducting coils, corresponding to 0.2-0.3 V/m. The operational conditions that lead to RE generation are evaluated to mitigate the risk of RE discharges. The simulation shows that startup REs are generated during the temperature rise immediately after the burn-through under relatively low-density conditions, and then the RE current value is gradually increased in balance with the RE loss processes on the timescale of $I_p$ ramp-up. Therefore, it is expected that REs can be avoided or mitigated if the electron density during the early build-up phase is tuned by a combination of prefill gas and additional fuelling. However, a startup with an excessive prefill gas will lose the margin of the density control, and a full RE discharge can be triggered when the plasma burn-through fails owing to a high concentration of impurities such as oxygen, if the operational point is marginal to the burn-through limit. The present modelling work implies that preparing the operation with sufficient margins against the failure of impurity burn-through is important for mitigating the risk of unintended plasma termination. Although the carbon wall environment may have a lower risk of RE generation, to alleviate the operational uncertainties of the new device, strategies for expanding the operational window are also discussed in support of JT-60SA initial operation.

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Section: Introductionmentioning

confidence: 99%

Modelling of ohmic startup and runaway electron formation in support of JT-60SA initial operation

Matsuyama¹,

Wakatsuki²,

Inoue³

et al. 2022

Nucl. Fusion

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“…On the other hand, scenario 5 is a high-beta scenario and is operated with a lower magnetic field than scenario 2, hence the RF frequency is switched to 110 GHz. Such operation switching at different frequencies is possible by employing multi-frequency gyrotrons [64]. In the following calculations, we assume a de-focused Gaussian beam with the waist w 0 = 17.97 mm and the center of the antenna (R, z) = (4.13, 0.8) m as the initial position of the RR.…”

Section: Simulation Results In Jt-60sa Tokamakmentioning

confidence: 99%

Broadening of electron cyclotron power deposition and driven current profiles caused by dissipative diffractive propagation

Yanagihara,

Kubo

2024

Nucl. Fusion

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Improvements of the Electron Cyclotron Resonance Heating (ECRH) and Current Drive (ECCD) predictions are important issues to design and control the high-performance fusion plasmas in future devices, where those should play a more important role as an actuator than in devices to date. The newly developed EC-prediction package based on the quasioptical ray tracing code PARADE revealed in JT-60SA that (i) radial profiles of both EC power deposition and driven current are broadened and (ii) the net driven current is increased by few kA/MW, in comparison with conventional predictions due to the dissipative diffractive propagation (DDP). The mechanism of DDP is as follows; EC wave beam obliquely passing through the resonant surface is dissipated non- uniformly on its beam cross section, so that the beam trajectory shifts gradually and thus the resonant position also shifts, resulting in the broadened power deposition profile. This novel ECCD and ECRH prediction package based on PARADE is applicable not only to JT-60SA but other existing devices and even, future devices.

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“…At its full development, the ECRF system is designed for 9 gyrotrons able to inject up to 7 MW to the plasma from 4 toroidally distributed upper oblique launchers with extended poloidal and toroidal steering capability and pulse duration up to 100 s. Each gyrotron can provide EC power at three different frequencies, namely 82, 110 and 138 GHz [4,5]. Before full performance will be made available, gradually increasing capabilities are foreseen for the Integrated Commissioning (IC) phase (~2023) and for the Initial Research phase (IR, ~2025-2026).…”

Section: Introductionmentioning

confidence: 99%

ECRF stray radiation studies in preparation of the operations of JT-60SA

et al. 2023

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JT-60SA tokamak is equipped with an ECRF system since the beginning of its operational phase. Starting from two gyrotrons units during the Integrated Commissioning, applicable for core heating, assisted breakdown and assisted Wall Conditioning, the system capabilities will be progressively extended from the Initial Research phase for wider applications. The development of the full current plasma H mode scenario 2 (inductive, type I ELM, Ip=5.5 MA, BT=2.25 T, q95=3) is among the first scientific objectives of the research program. In preparation of this, predictive modelling of the current ramp-up in scaled versions of scenario 2 is being done, based on parameters previously published. In this scenario the ECRF power is injected from an early phase of the discharge. Such modelling provides the kinetic profiles giving the opportunity to estimate the expected amount of EC stray radiation during the ramp-up phase when the EC power absorption might be less than 100% and consequently the potential risk of damage of the in-vessel components is higher.

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Development of high-power, long-pulse, multi-frequency ECH/CD system for JT-60SA

Cited by 7 publications

References 33 publications

Modelling of ohmic startup and runaway electron formation in support of JT-60SA initial operation

Modelling of ohmic startup and runaway electron formation in support of JT-60SA initial operation

Broadening of electron cyclotron power deposition and driven current profiles caused by dissipative diffractive propagation

ECRF stray radiation studies in preparation of the operations of JT-60SA

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