Li Li Yue Liu Yueqiang Liu
An analytic model of non-linear feedback stabilization of the resistive wall mode is presented. The non-linearity comes from either the current or the voltage saturation of the control coil power supply. For the so-called flux-to-current control, the current saturation of active coils always results in the loss of control. On the contrary, the flux…
PublishedPui-Wai Ma W. C. Liu C. H. Woo S. L. Dudarev
We perform large-scale molecular dynamics simulations to study the magnetic properties of amorphous iron under pressure. Simulations, exceeding by at least two orders of magnitude those accessible to density functional calculations, use the recently developed magnetic interatomic potential for iron. The distributions of the size of atomic magnetic …
PublishedG.Z. Hao Y.Q. Liu A.K. Wang H.B. Jiang Gaimin Lu H.D. He X.M. Qiu
A theoretical model for investigating the effect of the trapped energetic particles EPs on the resistive wall mode RWM instability is proposed. The results demonstrate that the trapped EPs have a dramatic stabilizing effect on the RWM because of resonant interaction between the mode and the magnetic precession drift motion of the trapped EPs. The r…
PublishedM. Okabayashi G. Matsunaga J.S. Degrassie W.W. Heidbrink Y. In Y.Q. Liu H. Reimerdes W.M. Solomon E.J. Strait M. Takechi N. Asakura R.V. Budny G.L. Jackson J.M. Hanson R. J. La Haye M.J. Lanctot J. Manickam K. Shinohara Y.B. Zhu
An energetic-particle (EP)-driven “off-axis-fishbone-like mode (OFM)” often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-b N discharges. In these experiments, the EPs are energetic ions (70–85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce t…
PublishedM.J. Lanctot H. Reimerdes A.M. Garofalo M.S. Chu J. M. Hanson Y.Q. Liu G.A. Navratil I.N. Bogatu Y. In G.L. Jackson R.J. La Haye M. Okayabashi J.-K. Park M.J. Schaffer O. Schmitz E.J. Strait A.D. Turnbull
A detailed experiment-theory comparison reveals that linear ideal MHD theory is in quantitative agreement with external magnetic and internal soft x-ray measurements of the plasma response to externally applied non-axisymmetric fields over a broad range of beta and rotation. This result represents a significant step toward the goal of advancing the…
PublishedIT Chapman MP Gryaznevich DF Howell YQ Liu The Mast Team
Resistive wall mode stability limits have been probed by MHD spectroscopy and numerical modelling. MAST plasmas have operated up to βN = 5.7, well above the predicted ideal kink no-wall limit or measured resonant field amplification limits due to a combination of rotation and kinetic damping. By varying the density, both the rotation and the fast …
PublishedD. Yadykin Y.Q. Liu R. Paccagnella
The kinetic effects, due to the mode resonance with thermal particle drift motions in the reversed field pinch (RFP) plasmas, are numerically investigated for the stability of the resistive wall mode, using a non-perturbative MHD-kinetic hybrid formulation. The kinetic effects are generally found too weak to substantially change the mode growth rat…
PublishedA. Kirk Yueqiang Liu E. Nardon P. Tamain P. Cahyna I. Chapman P. Denner H. Meyer S. Mordijck D. Temple The Mast Team
Experiments have been performed on MAST using internal (n=3) resonant magnetic perturbation coils. The application of the RMPs to L-mode discharges has shown a clear density pump out when the field line pitch angle at the low field side of the plasma is sufficiently well aligned with the applied field. The application of the RMPs before the L-H tra…
PublishedYueqiang Liu M.S. Chu W.F. Guo F. Villone R. Albanese G. Ambrosino M. Baruzzo T. Bolzonella I.T. Chapman A.M. Garofalo C.G. Gimblett R.J. Hastie T.C. Hender G.L. Jackson R.J. La Haye M.J. Lanctot Y.K. In G. Machiori M. Okabayashi R. Pac
Two issues of the resistive wall mode (RWM) control code maturity are addressed: the inclusion of advanced mode damping physics beyond the ideal MHD description, and the possibility of taking into account the influence of 3D features of the conducting structures on the mode stability and control. Examples of formulations and computational results a…
PublishedYueqiang Liu A. Kirk E. Nardon
The plasma response to resonant magnetic perturbation RMP and nonresonant perturbation fields is computed within a linear, full toroidal, single-fluid resistive magnetohydrodynamic framework. The response of resonant harmonics depends sensitively on the plasma resistivity and on the toroidal rotation. The response of nonresonant harmonics is not se…
Published