ECH pre-ionization and assisted startup in the fully superconducting KSTAR tokamak using second harmonic

Bae, Y.S.; Jeong, J.H.; Park, S.I.; Joung, M.; Kim, J.H.; Hahn, S. H.; Yoon, S.W.; Yang, H.L.; Kim, W.C.; Oh, Y.K.; England, A.C.; Namkung, W.; Cho, M.H.; Jackson, G.L.; Bak, J.S.

doi:10.1088/0029-5515/49/2/022001

Cited by 65 publications

(52 citation statements)

References 12 publications

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“…18 The relevance of ECH assistance is highlighted by the first experiments on KSTAR in 2008: ECH assistance was necessary to breakdown the first plasmas. 19 This access route to plasma formation was successively optimized and in 2010 even purely ohmic startup was achieved. A similar development route may be required in ITER.…”

Section: A Plasma Formationmentioning

confidence: 99%

Progress in preparing scenarios for operation of the International Thermonuclear Experimental Reactor

Sips

Giruzzi²,

Ide

et al. 2014

Physics of Plasmas

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The development of operating scenarios is one of the key issues in the research for ITER which aims to achieve a fusion gain (Q) of ∼10, while producing 500 MW of fusion power for ≥300 s. The ITER Research plan proposes a success oriented schedule starting in hydrogen and helium, to be followed by a nuclear operation phase with a rapid development towards Q ∼ 10 in deuterium/tritium. The Integrated Operation Scenarios Topical Group of the International Tokamak Physics Activity initiates joint activities among worldwide institutions and experiments to prepare ITER operation. Plasma formation studies report robust plasma breakdown in devices with metal walls over a wide range of conditions, while other experiments use an inclined EC launch angle at plasma formation to mimic the conditions in ITER. Simulations of the plasma burn-through predict that at least 4 MW of Electron Cyclotron heating (EC) assist would be required in ITER. For H-modes at q95 ∼ 3, many experiments have demonstrated operation with scaled parameters for the ITER baseline scenario at ne/nGW ∼ 0.85. Most experiments, however, obtain stable discharges at H98(y,2) ∼ 1.0 only for βN = 2.0–2.2. For the rampup in ITER, early X-point formation is recommended, allowing auxiliary heating to reduce the flux consumption. A range of plasma inductance (li(3)) can be obtained from 0.65 to 1.0, with the lowest values obtained in H-mode operation. For the rampdown, the plasma should stay diverted maintaining H-mode together with a reduction of the elongation from 1.85 to 1.4. Simulations show that the proposed rampup and rampdown schemes developed since 2007 are compatible with the present ITER design for the poloidal field coils. At 13–15 MA and densities down to ne/nGW ∼ 0.5, long pulse operation (>1000 s) in ITER is possible at Q ∼ 5, useful to provide neutron fluence for Test Blanket Module assessments. ITER scenario preparation in hydrogen and helium requires high input power (>50 MW). H-mode operation in helium may be possible at input powers above 35 MW at a toroidal field of 2.65 T, for studying H-modes and ELM mitigation. In hydrogen, H-mode operation is expected to be marginal, even at 2.65 T with 60 MW of input power. Simulation code benchmark studies using hybrid and steady state scenario parameters have proved to be a very challenging and lengthy task of testing suites of codes, consisting of tens of sophisticated modules. Nevertheless, the general basis of the modelling appears sound, with substantial consistency among codes developed by different groups. For a hybrid scenario at 12 MA, the code simulations give a range for Q = 6.5–8.3, using 30 MW neutral beam injection and 20 MW ICRH. For non-inductive operation at 7–9 MA, the simulation results show more variation. At high edge pedestal pressure (Tped ∼ 7 keV), the codes predict Q = 3.3–3.8 using 33 MW NB, 20 MW EC, and 20 MW ion cyclotron to demonstrate the feasibility of steady-state operation with the day-1 heating systems in ITER. Simulations using a lower edge pedestal temperature (∼3 keV) but improved core confinement obtain Q = 5–6.5, when ECCD is concentrated at mid-radius and ∼20 MW off-axis current drive (ECCD or LHCD) is added. Several issues remain to be studied, including plasmas with dominant electron heating, mitigation of transient heat loads integrated in scenario demonstrations and (burn) control simulations in ITER scenarios.

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Section: A Plasma Formationmentioning

confidence: 99%

Progress in preparing scenarios for operation of the International Thermonuclear Experimental Reactor

Sips

Giruzzi²,

Ide

et al. 2014

Physics of Plasmas

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show abstract

“…For KSTAR the situation is less clear. At least for the first ten degrees the delay is reduced [4]. To understand the difference between fundamental and 2nd harmonic resonance, the preionisation process has to be described in some more detail: As an ECR-beam is injected into the neutral gas without a plasma, it is reflected, diffused, de-polarised and damped on in-vessel components and an undefined mixture of O-and X-mode polarisation will fill the whole vessel.…”

Section: Ecrh Breakdown Assist With Toroidally Inclined Ecrhmentioning

confidence: 99%

“…The relevance of ECRH assist is highlighted by the first experiments on KSTAR in 2008: ECRH assist was necessary to break down the first plasmas [4]. This access route to plasma formation was successively optimised and in 2010 even purely ohmic breakdown was achieved [5].…”

Section: Introductionmentioning

confidence: 99%

ECRH-assisted plasma start-up with toroidally inclined launch: multi-machine comparison and perspectives for ITER

Stober¹,

Jackson²,

Ascasíbar³

et al. 2011

Nucl. Fusion

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Abstract. ECRH assisted plasma break down is foreseen with full and half magnetic field in ITER. As reported earlier, the corresponding O1-and X2-schemes have been successfully used for pre-ionisation and breakdown assist in present day devices. This contribution reports on common experiments studying the effect of toroidal inclination of the ECR beam, which is ≥ 20 • in ITER. All devices could demonstrate successful breakdown assist also for this case, although in some experiments the necessary power was almost a factor of two higher compared to perpendicular launch. Differences between the devices with regard to the required power and vertical field are discussed and analysed. In contrast to most of these experiments, ITER will build up loop voltage prior to the formation of the field null due to the strong shielding by the vessel. Possible consequences of this difference are discussed.

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“…Success in the ECH-assisted startup using 2nd harmonic [7] EC wave is expected to provide lots of crucial techniques for reliable startup with relatively low loop voltage (∼3 V) in superconducting tokamak devices. The KSTAR ECH-assisted startup system originally utilized 84 GHz gyrotron with a capability of 500 kW and 2 s pulse length.…”

Section: Ech/eccd Systemmentioning

confidence: 99%

Development of KSTAR in-vessel components and heating systems

Yang¹,

Park²,

Bae³

et al. 2011

Fusion Engineering and Design

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ECH pre-ionization and assisted startup in the fully superconducting KSTAR tokamak using second harmonic

Cited by 65 publications

References 12 publications

Progress in preparing scenarios for operation of the International Thermonuclear Experimental Reactor

Progress in preparing scenarios for operation of the International Thermonuclear Experimental Reactor

ECRH-assisted plasma start-up with toroidally inclined launch: multi-machine comparison and perspectives for ITER

Development of KSTAR in-vessel components and heating systems

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