Commissioning of the first KSTAR neutral beam injection system and beam experiments

Bae, Y.S.; Park, Y.M.; Kim, J.S.; Han, W.S.; Kwak, S.; Chang, Y.B.; Park, H.T.; Song, N.H.; Yang, H. L.; Yoon, S.W.; Jeon, Y.M.; Hahn, S.H.; Lee, S.G.; Ko, W. H.; England, A.C.; Kim, W.C.; Oh, Y.K.; Kwak, J.G.; Kwon, M.; Chang, Doo-Hee; Jeong, Seung Ho; Kim, T.S.; Oh, Byung-Hoon; Jin, J.; In, S.R.; Lee, K.W.; Watanabe, K.; Dairaku, M.; Tobari, H.; Kashiwagi, M.; Hanada, M.; Inoue, Takashi; Ikeda, Yujiro; Kawai, M.; Komata, M.; Mogaki, K.; Usui, K.; Yamamoto, Takashi; Matsuoka, M.; Nagaoka, K.; Grisham, L.

doi:10.1016/j.fusengdes.2012.05.011

Cited by 34 publications

(9 citation statements)

References 12 publications

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“…NBI is the main heating power in KSTAR. On-axis 1.2-1.4 MW NBI (90-95 keV) [19] were always injected in the co-current direction during the flap-top in the discharges presented here. There are two ECH heating system in KSTAR [20].…”

Section: Methodsmentioning

confidence: 99%

ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses

Shi

Kwon

et al. 2013

Nucl. Fusion

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Torodial rotation profiles have been investigated in KSTAR H-mode plasma using combined auxiliary heating by co-neutral beam injection (NBI) and electron cyclotron resonance heating (ECH). The ion temperature and toroidal rotation are measured with x-ray imaging crystal spectroscopy (XICS) and charge exchange recombination spectroscopy (CES).H-mode plasma is achieved using co-current 1.3MW NBI, and a 0.35 MW ECH pulse is added to the flattop of H-mode. The core rotation profiles, which are centrally peaked in the pure NBI heating phase, flatten when ECH is injected, while the edge pedestal is unchanged.Dramatic decreases in the core toroidal rotation values (V tor /V tor ~ -30%) are observed when on-axis ECH is added to H-mode. The experimental data shows that the decrease of core rotation velocity and its gradient are correlated with the increase of core electron temperature and its gradient, and also with the likely steepening of the density gradient. We thus explore the viability of a hypothesized ITG→TEM transition as the explanation of the observed counter-current flow induced by ECH. However, the results of linear microstability analyses using inferred profiles suggest that the TEM is excited only in the deep core, so the viability of the hypothesized explanation is not yet clear.PACS numbers: 52.55Hc, 52.55Fa, 52.50.Sw, 52.50.Gj IntroductionFlow and velocity shear are very important for stabilizing micro-and macro-instabilities in tokamak plasmas. Neutral beam injection (NBI) is generally used as the external momentum input source to produce and control plasma rotation in present day tokamaks. For ITER and future reactors, the input torque from NBI will be very low or nonexistent and cannot produce the needed rotation. As a result, there is a need to develop alternative or complementary methods for driving plasma rotation. Significant intrinsic rotation (without external momentum input) has been observed on many tokamaks [1], which suggests that it may be possible to reap the benefits of such self-generated flows in ITER and reactors.Since the discovery of intrinsic rotation in the 1990s [2, 3], plasma rotation without external torque has been a topic of intense interest. While significant progress has been made, the driving mechanism is not fully understood. Theoretical models have been proposed to explain intrinsic rotation as due to a turbulence driven intrinsic torque [4][5][6][7]. Intrinsic torque is dynamic and variable -due to evolving turbulent Reynolds stresses. Momentum transport bifurcations and reversals have been observed in several experiments [8,9]. The effects on toroidal rotation of ECH have being observed previously in CHS [10], DIII-D [11], JT-60U[12] and AUG [13,14]. The counter-current rotation increment or flattening of co-current rotation profile was confirmed in these ECH experiments. The proposed explanations vary considerably. The KSTAR results in this paper, though partly similar to some previous experiments, will be combined with gyrokinetic stability analyses to elucidate poss...

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Section: Methodsmentioning

confidence: 99%

ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses

Shi

Kwon

et al. 2013

Nucl. Fusion

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“…Each beamline system can accelerate the beam by up to 100 keV. 17,18 To model the prompt loss of injected beam ions during the KSTAR experiment, we adopted shot #14005, for which the three beamlines heat the plasma. The beam energies of NBI1-A, NBI1-B, and NBI1-C were set to 100, 70, and 70 keV, respectively.…”

Section: A Beam Modellingmentioning

confidence: 99%

Prompt loss of beam ions in KSTAR plasmas

et al. 2016

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For a toroidal plasma facility to realize fusion energy, researching the transport of fast ions is important not only due to its close relation to the heating and current drive efficiencies but also to determine the heat load on the plasma-facing components. We present a theoretical analysis and orbit simulation for the origin of lost fast-ions during neutral beam injection (NBI) heating in Korea Superconducting Tokamak Advanced Research (KSTAR) device. We adopted a two-dimensional phase diagram of the toroidal momentum and magnetic moment and describe detectable momentums at the fast-ion loss detector (FILD) position as a quadratic line. This simple method was used to model birth ions deposited by NBI and drawn as points in the momentum phase space. A Lorentz orbit code was used to calculate the fast-ion orbits and present the prompt loss characteristics of the KSTAR NBI. The scrape-off layer deposition of fast ions produces a significant prompt loss, and the model and experimental results closely agreed on the pitch-angle range of the NBI prompt loss. Our approach can provide wall load information from the fast ion loss. © 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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“…The first ion source was completed through a combination of a plasma source chamber developed by JAEA within the framework of the KO-JA fusion collaboration and an accelerator developed by KAERI. A longer pulse beam extraction was also demonstrated in 2011 and a 300 s duration beam at 80 keV was achieved [54]. For the NB system upgrade in 2012, the second ion source, which was developed by KAERI, and the associated power supplies and beam line components were newly installed.…”

Section: Heating and The Current Drive Systemmentioning

confidence: 99%

An overview of KSTAR results

Kwak¹,

Oh²,

Yang³

et al. 2013

Nucl. Fusion

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Since the first H-mode discharges in 2010, the duration of the H-mode state has been extended and a significantly wider operational window of plasma parameters has been attained. Using a second neutral beam (NB) source and improved tuning of equilibrium configuration with real-time plasma control, a stored energy of W tot ∼ 450 kJ has been achieved with a corresponding energy confinement time of τ E ∼ 163 ms. Recent discharges, produced in the fall of 2012, have reached plasma β N up to 2.9 and surpassed the n = 1 ideal no-wall stability limit computed for H-mode pressure profiles, which is one of the key threshold parameters defining advanced tokamak operation. Typical H-mode discharges were operated with a plasma current of 600 kA at a toroidal magnetic field B T = 2 T. L-H transitions were obtained with 0.8-3.0 MW of NB injection power in both single-and double-null configurations, with H-mode durations up to ∼15 s at 600 kA of plasma current. The measured power threshold as a function of lineaveraged density showed a roll-over with a minimum value of ∼0.8 MW at ne ∼ 2×10 19 m −3 . Several edge-localized mode (ELM) control techniques during H-mode were examined with successful results including resonant magnetic perturbation, supersonic molecular beam injection (SMBI), vertical jogging and electron cyclotron current drive injection into the pedestal region. We observed various ELM responses, i.e. suppression or mitigation, depending on the relative phase of in-vessel control coil currents. In particular, with the 90 • phase of the n = 1 RMP as the most resonant configuration, a complete suppression of type-I ELMs was demonstrated. In addition, fast vertical jogging of the plasma column was also observed to be effective in ELM pace-making. SMBI-mitigated ELMs, a state of mitigated ELMs, were sustained for a few tens of ELM periods. A simple cellular automata ('sand-pile') model predicted that shallow deposition near the pedestal foot induced small-sized high-frequency ELMs, leading to the mitigation of large ELMs. In addition to the ELM control experiments, various physics topics were explored focusing on ITER-relevant physics issues such as the alteration of toroidal rotation caused by both electron cyclotron resonance heating (ECRH) and externally applied 3D fields, and the observed rotation drop by ECRH in NB-heated plasmas was investigated in terms of either a reversal of the turbulence-driven residual stress due to the transition of ion temperature gradient to trapped electron mode turbulence or neoclassical toroidal viscosity (NTV) torque by the internal kink mode. The suppression of runaway electrons using massive gas injection of deuterium showed that runaway electrons were avoided only below 3 T in KSTAR. Operation in 2013 is expected to routinely exceed the n = 1 ideal MHD no-wall stability boundary in the long-pulse H-mode ( 10 s) by applying real-time shaping control, enabling n = 1 resistive wall mode active control studies. In addition, intensive works for ELM mitigation, ELM dynamics, toroidal ro...

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Commissioning of the first KSTAR neutral beam injection system and beam experiments

Cited by 34 publications

References 12 publications

ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses

ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses

Prompt loss of beam ions in KSTAR plasmas

An overview of KSTAR results

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