A5101561776- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Physics of Superconductivity and Magnetism
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Magnetic Bearings and Levitation Dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Computational Fluid Dynamics and Aerodynamics
- Quantum chaos and dynamical systems
- Dust and Plasma Wave Phenomena
Culham Science Centre
2018-2025
Culham Centre for Fusion Energy
2022-2025
Southwestern Institute of Physics
2016-2019
Dalian University of Technology
2014-2016
Abstract STEP is a spherical tokamak prototype power plant that being designed to demonstrate net electric power. The design phase involves the exploitation of plasma models optimise fusion performance subject satisfying various physics and engineering constraints. A modelling workflow, including integrated core modelling, MHD stability analysis, SOL pedestal coil set free boundary equilibrium solvers, whole design, has been developed specify parameters develop viable scenarios. model JETTO...
Abstract In 2019 the UK launched Spherical Tokamak for Energy Production (STEP) programme to design and build a prototype electricity producing nuclear fusion power plant, aiming start operation around 2040. The plant should lay foundation development of commercial plants. is based on spherical tokamak principle, which opens route high pressure, steady state, operation. While facilitating state operation, introduces some specific plasma control challenges: (i) All current during burn phase...
Abstract A novel approach for efficient representation of three-dimensional (3D) tokamak equilibria is investigated, where a set helical current filaments occupying the plasma region are employed to resolve deviations from two-dimensional (2D) axi-symmetric state. discrete 3D filaments, located at rational surfaces given toroidal mode number $n$ and following 2D equilibrium field lines (thus forming closed loops), found provide surrogate model with reasonable accuracy. Specifically,...
Abstract The MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), has been updated to include two-fluid (2F) effects for linear stability analysis of magnetohydrodynamic (MHD) modes. code, referred as MARS-2F, is then applied study flow stabilization the resistive wall mode (RWM) in a reactor-scale negative-triangularity (NT) plasma, with results also compared that obtained positive-triangularity counterpart. RWM computed be stable plasmas slow or even vanishing toroidal fluid according...
Toroidal computation of the plasma response to n = 2 (n is toroidal mode number) resonant magnetic perturbation field, based on an H-mode in DIII-D, carried out for purpose investigating role ideal versus resistive models while scanning safety factor (q) at edge. Both models, implemented MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), show significant amplification kink-peeling certain q-windows. A longstanding issue addressed this work sensitivity q-window smoothing X-point geometry...
Abstract The influence of negative triangularity (NT) the plasma shape on n = 1 (n is toroidal mode number) tearing (TM) stability has been numerically investigated, with results compared to that positive (PT) counterpart. By matching safety factor profile for a series equilibria, several important parameters, including triangularity, equilibrium pressure, resistivity as well rotation, have varied. TM localized near edge found be more unstable in NT plasmas PT fundamental reason this...
The synergetic effects of drift kinetic resonances, the resistive layer dissipation, magnetic feedback, and toroidal plasma flow on stability wall mode are numerically investigated using a full magnetohydrodynamic-kinetic hybrid code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503). It is found that resistivity, coupled with favourable average curvature effect, can enlarge stable domain predicted by model. A synergy between precessional resonance damping, feedback helps open two windows....
The combined effects of anisotropic thermal transport and the plasma shaping, including negative triangularity, on n = 1 (n is toroidal mode number) tearing (TM) stability are numerically investigated utilizing MARS-F code [Liu et al., Phys. Plasmas 7, 3681–3690 (2000)]. While varying boundary TM found to be dictated by competing Shafranov shift induced stabilization bad-curvature destabilization. triangularity shape increases (stabilizing) in core but also enlarges regions (destabilizing)...
The effects of an ideal/resistive conducting wall, the drift kinetic resonances, as well toroidal plasma flow, on stability ideal external kink mode are numerically investigated for a reactor-relevant tokamak with strongly negative triangularity (NTR) shaping. Comparison is made similar equilibrium, but positive (PTR). It found that wall stabilization less efficient in NTR due to 'external' eigenmode structure compared PTR plasma. associated displacement does not 'balloon' near outboard...
A dispersion relation is derived for the stability of resistive wall mode (RWM), which includes both layer damping physics and toroidal precession drift resonance from energetic ions in tokamak plasmas. The numerically solved a model plasma, purpose systematic investigation RWM multi-dimensional plasma parameter space including resistivity, radial location wall, as well flow velocity. It found that favorable average curvature contributes significant stabilization RWM. This further enhanced...
The synergetic effects of feedback and toroidal plasma rotation on the stability resistive wall mode are systematically investigated by a full magnetohydrodynamic code MARS-F (Liu Y Q et al 2000 Phys. Plasmas 7 3681). This synergy is studied for both ideal models. It found that magnetic scheme, combined with passive stabilization from flow, can open two windows as moves away plasma, opposed to single window opened flow alone. width new increases gain. frequency affects windows. achieved when...
Abstract In this work, the MARS-F/K codes (Liu et al 2000 Phys. Plasmas 7 3681; Liu 2008 15 112503) are utilized to model passive and active control of n = 1 ( is toroidal mode number) resistive wall (RWM) in a spherical tokamak (aspect ratio A 1.66). It found that stabilization RWM gives relatively small increase normalized beta above no-wall limit, relying on plasma flow drift kinetic resonance damping from both thermal energetic particles. Results show with flux-to-voltage scheme, which...
In ASDEX Upgrade hybrid discharges, it is found that an externally applied n = 1 field preferentially distorts the plasma in core, leading to significant flow damping there and elsewhere across radius. MARS-F/Q modeling of a neoclassical toroidal viscous NTV) torque results from amplified internal kink-type displacement core qualitatively consistent with measured displacements, beta dependence, rotation damping. Sensitivity studies indicate kink response resulting critically depend on...
Toroidal modeling efforts are initiated to systematically compute and compare various toroidal torques, exerted by an unstable internal kink in a tokamak plasma, using the MARS-F/K/Q suite of codes. The torques considered here include resonant electromagnetic torque due Maxwell stress (the EM or JXB torque), neoclassical viscous (NTV) torque, associated with Reynolds stress. Numerical results show that relative magnitude net increases equilibrium flow speed whilst NTV follows opposite trend....
Both an analytic model and the toroidal MARS-F code [Liu et al., Phys. Plasmas 7, 3681 (2000)] have been employed to study effect of anisotropic thermal transport on stability resistive wall mode (RWM) in tokamak plasmas. The results show that destabilizes plasma RWM, by effectively eliminating Glasser-Greene-Johnson favorable average curvature stabilization associated with layer [Glasser Fluids 875 (1975)]. Modification eigenfunction is also observed computations, due presence transport.
Active control of the n = 1 (n is toroidal mode number) resistive wall (RWM) numerically studied for an ITER 9 MA plasma designed advanced scenario. The large L/R response time active coils in results a significant reduction open-loop RWM growth rate, when act as passive conductors. For typical RWM, linear flux-to-voltage scheme, with proportional controller only, yields complex closed loop eigenvalue (in absence flow and drift kinetic effects), before fully stabilized by feedback. Without...
Abstract The resistive wall mode (RWM) control on the HL-2M tokamak is simulated with MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), aiming at quantifying current and voltage requirements when more realistic issues are taken into account, i.e. power saturation sensor signal noise. fluid model predicts a narrow stability region for n = 1 RWM without magnetic feedback, in 2D parameter space of plasma pressure versus toroidal flow speed. Magnetic feedback can fully stabilize HL-2M. Without...
Effects of toroidal plasma flow, magnetic drift kinetic damping as well feedback control, on the resistive wall mode instability in HL-2M tokamak are numerically investigated, using linear stability codes MARS-F/K (Liu et al 2000 Phys. Plasmas 7 3681, Liu 2008 15 112503). It is found that precession resonance due to trapped thermal particles ensures a robust passive stabilization n = 1 (n number) RWM 2 MA double-null advanced scenario designed for HL-2M, provided flow speed not too fast: ....
The effect of plasma with toroidal rotation on the resistive wall modes in tokamaks is studied numerically. An eigenvalue method adopted to calculate growth rate for changing resistivity and density distribution, as well diffusion time magnetic field through wall. It found that mode can be suppressed by plasma. Also, decreases when edge same core density, but it only changes slightly resistivity.
Systematic, multiple initial value simulations are performed for a toroidal plasma using the recently updated MARS-F code in order to understand how resistive wall mode (RWM) can be feedback controlled presence of control coil voltage saturation and/or sensor noise. The former renders nonlinear, thus generally requiring computations plasmas. This numerical study complements and confirms key results from previously analytic investigation RWM with power cylindrical [Li et al., Physics Plasmas,...
Non-linear interaction between the internal kink mode and toroidal plasma rotation is numerically studied using MARS-Q code [Liu et al., Phys. Plasmas 20, 042503 (2013)]. Simulation results show core flow damping due to various torques, generated by a weakly stable mode. The 3-D field perturbation induced including neoclassical viscous (NTV) torque, as well that produced Maxwell Reynolds stresses, act sink terms in momentum balance model. NTV torque found play dominant role all cases...
Modification of the external tearing index, Δext′, by magnetic feedback is analytically investigated for purpose controlling resistive plasma wall mode (RP-RWM). The matching method pursued deriving expressions close-loop Δext′ and linking it to counterpart from inner layer. Various coil configurations are found generally reduce stabilize RWM, with either proportional or derivative control. Feedback modification be independent layer interchange index DR, confirming that action primarily...
Non-linear interaction between the edge localized infernal mode (ELIM) and plasma toroidal flow is numerically investigated, by solving initial value problem for n = 1 ELIM, where number. The linear results show that ELIM instability strongly affected a close-fitting resistive wall. presence of wall can fully stabilize an otherwise flow-shear destabilized ELIM. computed torques based on eigenfunctions different radial distributions: neoclassical viscous torque has global distribution, whilst...