G. Z. Hao Y. Q. Liu A. K. Wang G. Matsunaga M. Okabayashi et al.
The kinetic effect of trapped energetic particles (EPs), arising from perpendicular neutral beam injection, on the stable low-n peeling modes in tokamak plasmas is investigated, through numerical solution of the mode’s dispersion relation derived from an energy principle. A resistive-wall peeling mode with m/n = 6/1, with m and n being the poloid…
PublishedA. D. Turnbull N. M. Ferraro V. A. Izzo E. A. Lazarus J.-K. Park W. A. Cooper S. P. Hirshman L. L. Lao M. J. Lanctot S. Lazerson Y. Q. Liu A. Reiman F. Turco
With the installation of non-axisymmetric coil systems on major tokamaks for the purpose of studying the prospects of ELM-free operation, understanding the plasma response to the applied fields is a crucial issue. Application of different response models, using standard tools, to DIII-D discharges with applied non-axisymmetric fields from internal …
PublishedYueqiang Liu A. Kirk Y. Sun
A toroidal, quasi-linear model is proposed to study the penetration dynamics of the resonant magnetic perturbation (RMP) field into the plasma. The model couples the linear, fluid plasma response to a toroidal momentum balance equation, which includes torques induced by both fluid electromagnetic force and by (kinetic) neoclassical toroidal viscous…
PublishedYueqiang Liu Youwen Sun
The non-linear interplay between the resistive wall mode (RWM) and the toroidal plasma flow is numerically investigated in a full toroidal geometry, by simultaneously solving the initial value problems for the n¼1 RW and the n¼0 toroidal force balance equation. Here, n is the toroidal mode number. The neoclassical toroidal viscous torque is ident…
PublishedC.J. Ham J.W. Connor S.C. Cowley R.J. Hastie T.C. Hender Y.Q. Liu
Calculations of tearing mode stability in tokamaks split conveniently into an external region, where marginally stable ideal MHD is applicable, and a resonant layer around the rational surface where sophisticated kinetic physics is needed. These two regions are coupled by the stability parameter △'. Pressure and current perturbations local…
PublishedA. Kirk I.T. Chapman T.E. Evans C. Ham J.R. Harrison G. Huijsmans Y. Liang Y.Q. Liu A. Loarte W. Suttrop A.J. Thornton
All current estimations of the energy released by type I ELMs indicate that, in order to ensure an adequate lifetime of the divertor targets on ITER, a mechanism is required to decrease the amount of energy released by an ELM, or to eliminate ELMs altogether. One such amelioration mechanism relies on perturbing the magnetic field in the edge plasma…
PublishedA.Kirk I.T. Chapman Yueqiang Liu P. Cahyna P. Denner G. Fishpool C.J. Ham J.R. Harrison Yunfeng Liang E. Nardon S. Saarelma R. Scannell A.J. Thornton The Mast Team
Sustained ELM mitigation has been achieved using RMPs with a toroidal mode number of n=4 and n=6 in lower single null and with n=3 in connected double null plasmas on MAST. The ELM frequency increases by up to a factor of eight with a similar reduction in ELM energy loss. A threshold current for ELM mitigation is observed above which the ELM freque…
PublishedI. T. Chapman A. Kirk C. J. Ham J. R. Harrison Y. Q. Liu et al.
Type-I Edge Localised Modes (ELMs) have been mitigated in MAST through the application of n = 3, 4, and 6 resonant magnetic perturbations. For each toroidal mode number of the non-axisymmetric applied fields, the frequency of the ELMs has been increased significantly, and the peak heat flux on the divertor plates reduced commensurately. This increa…
PublishedYueqiang Liu J. W. Connor S. C. Cowley C. J. Ham R. J. Hastie et al.
A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even i…
PublishedYueqiang Liu R. J. Hastie T. C. Hender
Two possible ways of modifying the linear tearing mode index, by active magnetic feedback and by drift kinetic effects of deeply trapped particles, are analytically investigated. Magnetic feedback schemes, studied in this work, are found generally stabilizing for Δ′. The drift kinetic effects from both thermal particles and hot ions tend to redu…
Published