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J. Manickam

Bio: J. Manickam is an academic researcher from Princeton Plasma Physics Laboratory. The author has contributed to research in topics: Tokamak & Magnetic confinement fusion. The author has an hindex of 25, co-authored 36 publications receiving 2939 citations.

Papers
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Journal ArticleDOI
TL;DR: A review of recent advances in the area of MHD stability and disruptions, since the publication of the 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137-2664), is reviewed in this paper.
Abstract: Progress in the area of MHD stability and disruptions, since the publication of the 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137-2664), is reviewed. Recent theoretical and experimental research has made important advances in both understanding and control of MHD stability in tokamak plasmas. Sawteeth are anticipated in the ITER baseline ELMy H-mode scenario, but the tools exist to avoid or control them through localized current drive or fast ion generation. Active control of other MHD instabilities will most likely be also required in ITER. Extrapolation from existing experiments indicates that stabilization of neoclassical tearing modes by highly localized feedback-controlled current drive should be possible in ITER. Resistive wall modes are a key issue for advanced scenarios, but again, existing experiments indicate that these modes can be stabilized by a combination of plasma rotation and direct feedback control with non-axisymmetric coils. Reduction of error fields is a requirement for avoiding non-rotating magnetic island formation and for maintaining plasma rotation to help stabilize resistive wall modes. Recent experiments have shown the feasibility of reducing error fields to an acceptable level by means of non-axisymmetric coils, possibly controlled by feedback. The MHD stability limits associated with advanced scenarios are becoming well understood theoretically, and can be extended by tailoring of the pressure and current density profiles as well as by other techniques mentioned here. There have been significant advances also in the control of disruptions, most notably by injection of massive quantities of gas, leading to reduced halo current fractions and a larger fraction of the total thermal and magnetic energy dissipated by radiation. These advances in disruption control are supported by the development of means to predict impending disruption, most notably using neural networks. In addition to these advances in means to control or ameliorate the consequences of MHD instabilities, there has been significant progress in improving physics understanding and modelling. This progress has been in areas including the mechanisms governing NTM growth and seeding, in understanding the damping controlling RWM stability and in modelling RWM feedback schemes. For disruptions there has been continued progress on the instability mechanisms that underlie various classes of disruption, on the detailed modelling of halo currents and forces and in refining predictions of quench rates and disruption power loads. Overall the studies reviewed in this chapter demonstrate that MHD instabilities can be controlled, avoided or ameliorated to the extent that they should not compromise ITER operation, though they will necessarily impose a range of constraints.

1,051 citations

Journal ArticleDOI
G.S. Lee, J.Y. Kim, S.M. Hwang, Choong-Seock Chang1, H.Y. Chang1, Moo-Hyun Cho2, B.H. Choi, Kyekyoon Kim3, K.W. Cho, S.Y. Cho, K.K. Choh, C.H. Choi, J.H. Choi, J.W. Choi, I.S. Choi, C.J. Do, T.H. Ha, J.H. Han, J.S. Hong, K.H. Hong, N.I. Hur, I.S. Hwang, K.H. Im, H.G. Jhang, Y.S. Jung, B.C. Kim, D.L. Kim, G.H. Kim, H.S. Kim, J.S. Kim, J.Y. Kim, W.C. Kim, Y.S. Kim4, K.H. Kwon, M.C. Kyum, B.J. Lee, D.K. Lee, H.G. Lee, J.M. Lee, S.G. Lee, H.G. Na, Y.K. Oh, J.H. Park, H.C. Ri, Y.S. Ryoo, K.Y. Song, H.L. Yang, J.G. Yang, B.J. Yoo, S.J. Yoo, N.S. Yoon, S.B. Yoon, G.H. You, K.I. You, Wonho Choe1, D.-I. Choi1, S.G. Jeong1, D.Y. Lee1, Young-Soon Bae2, H.S. Kang2, G.N. Kim2, I.S. Ko2, Won Namkung2, J.S. Oh2, Y.D. Bae, Y.S. Cho, B.G. Hong, G. Hong, C.K. Hwang, S.R. In, M.H. Ju, H.J. Lee, B.H. Oh, B.J. Yoon, S. Baang3, H.J. Choi3, J. Hwang3, M.G. Kim3, Y.J. Kim3, Soonil Lee3, J. Yee3, C.S. Yoon3, K.-H. Chung5, SeulChan Hong5, Yong-Seok Hwang5, S.H. Kim5, YooSung Kim5, J.Y. Lim6, D.W. Ha7, S.S. Oh7, K.S. Ryu7, Q.L. Wang7, T.K. Ko8, J. Joo, S. Suh, J.H. Lee, Y.W. Lee, H.S. Shin, I.H. Song, J. Baek, I.Y. Han, Y. Koh, P.Y. Park, C. Ryu9, J.J. Cho4, D.M. Hwang4, J. A. Schmidt10, Hyeon K. Park10, George H. Neilson10, W. Reiersen10, R.T. Simmons10, S. Bernabei10, F. Dahlgren10, Larry R. Grisham10, Stephen Jardin10, C.E. Kessel10, J. Manickam10, S. S. Medley10, Neil Pomphrey10, J.C. Sinnis10, Thomas Brown10, Roscoe White10, K. Young10, J.H. Schultz11, P.W. Wang11, L. Sevier12, Mark D. Carter13, P.M. Ryan13, D.W. Swain13, D. N. Hill14, W. M. Nevins14, Bastiaan J. Braams15 
TL;DR: The Korea Superconducting Tokamak Advanced Research (KSTAR) project is the major effort of the national fusion programme of the Republic of Korea as mentioned in this paper, which aims to develop a steady state capable advanced superconducting tokamak to establish a scientific and technological basis for an attractive fusion reactor.
Abstract: The Korea Superconducting Tokamak Advanced Research (KSTAR) project is the major effort of the national fusion programme of the Republic of Korea. Its aim is to develop a steady state capable advanced superconducting tokamak to establish a scientific and technological basis for an attractive fusion reactor. The major parameters of the tokamak are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 T and plasma current 2 MA, with a strongly shaped plasma cross-section and double null divertor. The initial pulse length provided by the poloidal magnet system is 20 s, but the pulse length can be increased to 300 s through non-inductive current drive. The plasma heating and current drive system consists of neutral beams, ion cyclotron waves, lower hybrid waves and electron cyclotron waves for flexible profile control in advanced tokamak operating modes. A comprehensive set of diagnostics is planned for plasma control, performance evaluation and physics understanding. The project has completed its conceptual design and moved to the engineering design and construction phase. The target date for the first plasma is 2002.

185 citations

Journal ArticleDOI
TL;DR: Edge stability calculations indicate that the pre- Li discharges were unstable to low-n peeling or ballooning modes, while broader pressure profiles stabilized the post-Li discharges, which indicated normalized energy confinement increased by 50% post Li.
Abstract: Reduction or elimination of edge localized modes (ELMs) while maintaining high confinement is essential for future fusion devices, e.g., the ITER. An ELM-free regime was recently obtained in the National Spherical Torus Experiment, following lithium (Li) evaporation onto the plasma-facing components. Edge stability calculations indicate that the pre-Li discharges were unstable to low-n peeling or ballooning modes, while broader pressure profiles stabilized the post-Li discharges. Normalized energy confinement increased by 50% post Li, with no sign of ELMs up to the global stability limit.

156 citations

Journal ArticleDOI
TL;DR: The role of shear in determining the ideal MHD stability properties of tokamaks is discussed in this article, where the effects of low shear within the plasma upon pressure driven modes are assessed.
Abstract: The role of shear in determining the ideal MHD stability properties of tokamaks is discussed. In particular, the effects of low shear within the plasma upon pressure driven modes are assessed. The standard ballooning theory is shown to break down as the shear is reduced, and the growth rate is shown to be an oscillatory function of n, the toroidal mode number, treated as a continuous parameter. The oscillations are shown to depend on both the pressure profile and the safety factor profile. When the shear is sufficiently weak, the oscillations can result in bands of unstable n-values, which are present even when the standard ballooning theory predicts complete stability. These instabilities are named 'infernal modes'. The occurrence of these instabilities at integer n is shown to be a sensitive function of the q-axis, raising the possibility of a sharp onset as the plasma parameters evolve.

152 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of toroidal and poloidal flows on the equilibrium of tokamak plasmas are numerically investigated using the FLOW code and the results confirm the conclusions of the analytic theory of R. Betti and J. Freidberg.
Abstract: The effects of toroidal and poloidal flows on the equilibrium of tokamak plasmas are numerically investigated using the code FLOW. The code is used to determine the changes in the profiles induced by large toroidal flows on NSTX-like equilibria [with NSTX being the National Spherical Torus Experiment, M. Ono, S.M. Kaye, Y.-K.M. Peng et al., Nucl. Fusion 40, 557 (2000)] where flows exceeding the sound speed lead to a considerable outward shift of the plasma. The code is also used to study the effects of poloidal flow when the flow velocity profile varies from subsonic to supersonic with respect to the poloidal sound speed. It is found that pressure and density profiles develop a pedestal structure characterized by radial discontinuities at the transonic surface where the poloidal velocity abruptly jumps from subsonic to supersonic values. These results confirm the conclusions of the analytic theory of R. Betti and J. P. Freidberg [Phys. Plasmas 7, 2439 (2000)], derived for a low-β, large aspect ratio tokamak with a circular cross section.

127 citations


Cited by
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Journal ArticleDOI
TL;DR: The nonlinear gyrokinetic equations play a fundamental role in our understanding of the long-time behavior of strongly magnetized plasmas as mentioned in this paper, and they have been used to describe the turbulent evolution of low-frequency electromagnetic fluctuations in a nonuniform magnetization with arbitrary magnetic geometry.
Abstract: Nonlinear gyrokinetic equations play a fundamental role in our understanding of the long-time behavior of strongly magnetized plasmas. The foundations of modern nonlinear gyrokinetic the- ory are based on three important pillars: (1) a gyrokinetic Vlasov equation written in terms of a gyrocenter Hamiltonian with quadratic low-frequency ponderomotive-like terms; (2) a set of gyrokinetic Maxwell (Poisson-Ampere) equations written in terms of the gyrocenter Vlasov dis- tribution that contain low-frequency polarization (Poisson) and magnetization (Ampere) terms derived from the quadratic nonlinearities in the gyrocenter Hamiltonian; and (3) an exact energy conservationlaw for the gyrokineticVlasov-Maxwell equations that includes all the relevant linear and nonlinear coupling terms. The foundations of nonlinear gyrokinetic theory are reviewed with an emphasis on the rigorous applications of Lagrangian and Hamiltonian Lie-transform perturba- tion methods used in the variationalderivationof nonlineargyrokineticVlasov-Maxwell equations. The physical motivations and applications of the nonlinear gyrokinetic equations, which describe the turbulent evolution of low-frequency electromagnetic fluctuations in a nonuniform magnetized plasmas with arbitrary magnetic geometry, are also discussed.

1,010 citations

Journal ArticleDOI
TL;DR: The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions.
Abstract: The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions. Very considerable progress has been made in understanding, controlling and predicting tokamak transport across a wide variety of plasma conditions and regimes since the publication of the ITER Physics Basis (IPB) document (1999 Nucl. Fusion 39 2137-2664). Major areas of progress considered here follow. (1) Substantial improvement in the physics content, capability and reliability of transport simulation and modelling codes, leading to much increased theory/experiment interaction as these codes are increasingly used to interpret and predict experiment. (2) Remarkable progress has been made in developing and understanding regimes of improved core confinement. Internal transport barriers and other forms of reduced core transport are now routinely obtained in all the leading tokamak devices worldwide. (3) The importance of controlling the H-mode edge pedestal is now generally recognized. Substantial progress has been made in extending high confinement H-mode operation to the Greenwald density, the demonstration of Type I ELM mitigation and control techniques and systematic explanation of Type I ELM stability. Theory-based predictive capability has also shown progress by integrating the plasma and neutral transport with MHD stability. (4) Transport projections to ITER are now made using three complementary approaches: empirical or global scaling, theory-based transport modelling and dimensionless parameter scaling (previously, empirical scaling was the dominant approach). For the ITER base case or the reference scenario of conventional ELMy H-mode operation, all three techniques predict that ITER will have sufficient confinement to meet its design target of Q = 10 operation, within similar uncertainties.

798 citations

Journal ArticleDOI
TL;DR: The progress in the ITER Physics Basis (PIPB) document as discussed by the authors is an update of the IPB, which was published in 1999 [1], and provides methodologies for projecting the performance of burning plasmas, developed largely through coordinated experimental, modelling and theoretical activities carried out on today's large tokamaks (ITER Physics R&D).
Abstract: The 'Progress in the ITER Physics Basis' (PIPB) document is an update of the 'ITER Physics Basis' (IPB), which was published in 1999 [1]. The IPB provided methodologies for projecting the performance of burning plasmas, developed largely through coordinated experimental, modelling and theoretical activities carried out on today's large tokamaks (ITER Physics R&D). In the IPB, projections for ITER (1998 Design) were also presented. The IPB also pointed out some outstanding issues. These issues have been addressed by the Participant Teams of ITER (the European Union, Japan, Russia and the USA), for which International Tokamak Physics Activities (ITPA) provided a forum of scientists, focusing on open issues pointed out in the IPB. The new methodologies of projection and control are applied to ITER, which was redesigned under revised technical objectives. These analyses suggest that the achievement of Q > 10 in the inductive operation is feasible. Further, improved confinement and beta observed with low shear (= high βp = 'hybrid') operation scenarios, if achieved in ITER, could provide attractive scenarios with high Q (> 10), long pulse (>1000 s) operation with beta

706 citations

Journal ArticleDOI
TL;DR: In this paper, a model based on magnetohydrodynamic stability of the tokamak plasma edge region is presented, which describes characteristics of edge localized modes (ELMs) and the pedestal.
Abstract: A model based on magnetohydrodynamic (MHD) stability of the tokamak plasma edge region is presented, which describes characteristics of edge localized modes (ELMs) and the pedestal. The model emphasizes the dual role played by large bootstrap currents driven by the sharp pressure gradients in the pedestal region. Pedestal currents reduce the edge magnetic shear, stabilizing high toroidal mode number (n) ballooning modes, while at the same time providing drive for intermediate to low n peeling modes. The result is that coupled peeling–ballooning modes at intermediate n (3

684 citations

Proceedings ArticleDOI
23 Jun 2008
TL;DR: This paper discusses the concept of ldquocloudrdquo computing, issues it tries to address, related research topics, and a ldquistocloud thirdquo implementation available today.
Abstract: ldquoCloudrdquo computing - a relatively recent term, builds on decades of research in virtualization, distributed computing, utility computing, and more recently networking, web and software services. It implies a service oriented architecture, reduced information technology overhead for the end-user, great flexibility, reduced total cost of ownership, on-demand services and many other things. This paper discusses the concept of ldquocloudrdquo computing, issues it tries to address, related research topics, and a ldquocloudrdquo implementation available today.

609 citations