Electron fishbone dynamics studies in tokamaks using the XHMGC code
نویسندگان
چکیده
The electron fishbone modes are internal kink instabilities induced by suprathermal electrons. Ion fishbones were first observed experimentally (PDX) [1], opening the path to full theoretical understanding of these phenomena [4]. Stimulated by experimental evidence of electron fishbones (DIII-D, Compass-D, FTU, ToreSupra), theoretical analysis has also been extended to the case of modes excited by fast electrons [5]. It is well known that additional heating of a plasma produces suprathermal particles which, under certain conditions, could destabilize symmetry breaking modes. Moreover, the dynamics of suprathermal electrons in present days experiments has analogies to that of alpha particles in future burning plasma devices; and resonant excitation by fast electron precession resonance may provide a good test bed for understanding the similar mechanism induced by fusion alphas. For these reasons, it is important to get insights into the underlying physics processes involved in these phenomena. In this work, numerical simulations with the HMGC code [6] are systematically carried out in tokamak equilibria. On the one side, theoretical and experimental results are confirmed, while, on the other side, numerical simulations give a deeper insight into the e-fishbones dynamics. Linear and non-linear studies of e-fishbone instability have been performed for standard (peaked on-axis) [7] and inverted (peaked off-axis) suprathermal electron density profile, with moderately hollow q-profile. It is worth noting that the two situations are significantly different in terms of the characteristic resonance frequency as well as the fraction of suprathermal particles involved in the destabilization of the mode, confirming theoretical expectations. The study of e-fishbone nonlinear saturation mechanisms uses the test particle Hamiltonian method (TPHM) package [8], illuminating the complicate and unexplored dynamics of these modes.
منابع مشابه
Electron fishbone simulations in tokamak equilibria using XHMGC
This paper discusses the first nonlinear numerical simulation results of fishbone excitation by a magnetically trapped supra-thermal electron population with pressure profile peaked on axis due to, e.g. electron cyclotron resonance heating. The precession resonance underlying the linear instability is clearly identified. Meanwhile, mode saturation is shown to occur because of the secular resona...
متن کاملElectron Fishbone Simulations in FTU-Like Equilibria Using XHMGC
Abstract. This work discusses the first numerical simulation results of fishbone excitation by a suprathermal electron population due to, e.g., electron cyclotron resonance heating and/or lower hybrid wave current drive. The precession resonance underlying the linear instability is clearly identified. Meanwhile, mode saturation is shown to occur because of the secular resonant particle motion, ...
متن کاملGlobal Hybrid Simulations of Energetic Particle Effects on the n=1 Mode in Tokamaks: Internal Kink and Fishbone Instability
Global hybrid simulations of energetic particle effects on the n=1 internal kink mode have been carried out for tokamaks. For the Internationa Thermonuclear Experimental Reactor (ITER) [ITER Physics Basis Editors et al, Nucl. Fusion 3 ̄ 9, 2137 (1999).], it is shown that alpha particle effects are stabilizing for the internal kink mode. However, the elongation of ITER reduces the stabilization e...
متن کاملNumerical Studies and Simulation of the Lower Hybrid Waves Current Drive by using Fokker – Planck Equation in NSST and HT-7 Tokamaks
Recent experiments on the spherical tokamak have discovered the conditions to create a powerful plasma and ensure easy shaping and amplification of stability, high bootstrap current and confinement energy. The spherical tours (ST) fusion energy development path is complementary to the tokamak burning plasma experiment such as NSTX and higher toroidal beta regimes and improves the design of a po...
متن کاملOn the structure of wave-particle interactions and nonlinear Alfvénic fluctuation dynamics
Nonlinear dynamics, such as saturation and frequency chirping of Alfvénic fluctuations driven by energetic particles are investigated by means of the nonlinear hybrid magnetohydrodynamics gyrokinetic code (XHMGC). Saturation mechanism due to resonance detuning and/or radial decoupling are discussed. It will be shown that saturation field level exhibits a quadratic scaling with the growth rate, ...
متن کامل