Y. In

Ulsan National Institute of Science and Technology

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M. Okabayashi

Princeton University

E. J. Strait

General Atomics (United States)

H. Reimerdes

École Polytechnique Fédérale de Lausanne

Y.M. Jeon

Korea Institute of Fusion Energy

G.L. Jackson

General Atomics (United States)

R.J. La Haye

General Atomics (United States)

M.J. Lanctot

United States Department of Energy

A. M. Garofalo

General Atomics (United States)

Jong-Kyu Park

Princeton Plasma Physics Laboratory

S.H. Hahn

Korea Institute of Fusion Energy

Cooperative Institutions

General Atomics (United States)

443

Princeton Plasma Physics Laboratory

391

Fusion (United States)

317

Fusion Academy

298

Korea Institute of Fusion Energy

280

Princeton University

219

Oak Ridge National Laboratory

204

Lawrence Livermore National Laboratory

171

University of California, San Diego

170

Massachusetts Institute of Technology

168

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Overview of KSTAR initial operation

Nuclear Fusion (2011)

M. Kwon Y.K. Oh H.L. Yang Hanah Na Y.S. Kim

Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008–2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

KSTAR

Upgrade

10.1088/0029-5515/51/9/094006

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Citations (78)

Coupled evolution of temperature and flow profiles and turbulence near the magnetic island

M. Choi J. Kim J. M. Kwon H. K. Park Y. In

Multiscale interaction between the magnetic island and turbulence has been demonstrated through simultaneous two-dimensional measurements of turbulence and temperature and flow profiles. The magnetic island and turbulence mutually interact via the coupling between the electron temperature ($T_e$) gradient, the $T_e$ turbulence, and the poloidal flow. The $T_e$ gradient altered by the magnetic island is peaked outside and flattened inside the island. The $T_e$ turbulence can appear in the increased $T_e$ gradient regions. The combined effects of the $T_e$ gradient and the the poloidal flow shear determine two-dimensional distribution of the $T_e$ turbulence. When the reversed poloidal flow forms, it can maintain the steepest $T_e$ gradient and the magnetic island acts more like a electron heat transport barrier. Interestingly, when the $T_e$ gradient, the $T_e$ turbulence, and the flow shear increase beyond critical levels, the magnetic island turns into a fast electron heat transport channel, which directly leads to the minor disruption.

Temperature Gradient

Electron temperature

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Measurements of the high confinement mode pedestal region on Alcator C-Mod

Physics of Plasmas (1998)

A. Hubbard R. L. Boivin R. Granetz M. Greenwald I. H. Hutchinson

Measurements of the steep transport barrier at the edge of the Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] are presented. The parameters at the top of this barrier are in the range Te=150–750 eV and ne=0.5−3.3×1020 m−3, depending on the confinement regime. Type III edge localized modes (ELMs) have an upper temperature limit. Te pedestal profiles show a barrier width ΔT≃8 mm. Soft x-ray emissivity profiles are narrower, with Δ=2–4 mm. Edge currents are calculated to alter the ideal stability boundary favorably, leading to ideally stable pedestal profiles. High frequency, broadband, edge density fluctuations are sometimes observed in H-mode (high-confinement mode) and are associated with enhanced particle transport. Coherent magnetic fluctuations localized near the pedestal are also seen.

Alcator C-Mod

Pedestal

10.1063/1.872843

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Citations (49)

Feedback Control of (2,1) Mode in q$_edge\sim$2 Tokamak Plasma in RFX-MOD

Bulletin of the American Physical Society (2010)

Piero Martín R. Cavazzana L. Marrelli M. Baruzzo T. Bolzonella

Mod

Alcator C-Mod

Mode (computer interface)

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Observations of fast ion loss to the plasma facing wall during quiescent H-modes on DIII-D

Journal of Nuclear Materials (2005)

W.P. West C.J. Lasnier J.G. Watkins J.S. deGrassie Y. In

DIII-D

Pedestal

Edge-localized mode

Neutral Beam Injection

10.1016/j.jnucmat.2004.09.071

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Citations (8)

Observation of resonant and non-resonant magnetic braking in then= 1 non-axisymmetric configurations on KSTAR

Nuclear Fusion (2017)

Kimin Kim Wonho Choe Y. In W.H. Ko M. Choi

Toroidal rotation braking by neoclassical toroidal viscosity driven by non-axisymmetric (3D) magnetic fields, called magnetic braking, has great potential to control rotation profile, and thereby modify tokamak stability and performance. In order to characterize magnetic braking in the various 3D field configurations, dedicated experiments have been carried out in KSTAR, applying a variety of static , 3D fields of different phasing of , 0, and . Resonant-type magnetic braking was achieved by phasing fields, accompanied by strong density pump-out and confinement degradation, and explained by excitation of kink response captured by ideal plasma response calculation. Strong resonant plasma response was also observed under phasing at , leading to severe confinement degradation and eventual disruption by locked modes. Such a strong resonant transport was substantially modified to non-resonant-type transport at higher , as the resonant particle transport was significantly reduced and the rotation braking was pushed to plasma edge. This is well explained by ideal perturbed equilibrium calculations indicating the strong kink coupling at lower is reduced at higher discharge. The 0 phasing fields achieved quiescent magnetic braking without density pump-out and confinement degradation, which is consistent with vacuum and ideal plasma response analysis predicting deeply penetrating 3D fields without an excitation of strong kink response.

KSTAR

Resonant magnetic perturbations

10.1088/1741-4326/aa8382

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Citations (17)

Transient Neutron Production During ICRF Heating on Alcator C-Mod

APS Division of Plasma Physics Meeting Abstracts (1998)

C. L. Fiore R. L. Boivin A. Hubbard Y. In J. Irby

Alcator C-Mod

Transient (computer programming)

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