Alpha particle driven Alfvénic instabilities in ITER post-disruption plasmas

Abstract

Fusion-born alpha particles in ITER disruption simulations are investigated as a possible drive of Alfvénic instabilities. The ability of these waves to expel runaway electron (RE) seed particles is explored in the pursuit of a passive, inherent RE mitigation scenario. The spatiotemporal evolution of the alpha particle distribution during the disruption is calculated using the linearized Fokker-Planck solver CODION coupled to a fluid disruption simulation. These simulations are done in the limit of no alpha particle transport during the thermal quench, which can be seen as a most pessimistic situation where there is also no RE seed transport. Under these assumptions, the radial anisotropy of the resulting alpha population provides free energy to drive Alfvénic modes during the quench phase of the disruption. We use the linear gyrokinetic magnetohydrodynamic code LIGKA to calculate the Alfvén spectrum and find that the equilibrium is capable of sustaining a wide range of modes. The self-consistent evolution of the mode amplitudes and the alpha distribution is calculated utilizing the wave-particle interaction tool HAGIS. Intermediate mode number ($n=7-15,22-26$) Toroidal Alfvén Eigenmodes (TAEs) are shown to saturate at an amplitude of up to $\delta B/B\approx 0.1$\% in the spatial regimes crucial for RE seed formation. We find that the mode amplitudes are predicted to be sufficiently large to permit the possibility of significant radial transport of runaway electrons.

References in corpus (14)

• Influence of massive material injection on avalanche runaway generation during tokamak disruptions
• Pion Condensation by Rotation in a Magnetic field
• Runaway dynamics in the DT phase of ITER operations in the presence of massive material injection
• Nonlinear Energetic Particle Transport in the Presence of Multiple Alfvenic Waves in ITER
• The effect of ITER-like wall on runaway electron generation in JET
• Experimental investigation of the radial structure of energetic particle driven modes
• Effects of magnetic perturbations and radiation on the runaway avalanche
• Energetic electron transport in the presence of magnetic perturbations in magnetically confined plasmas
• Multi-mode Alfvénic Fast Particle Transport and Losses: Numerical vs. Experimental Observation
• The effects of kinetic instabilities on the electron cyclotron emission from runaway electrons
• Quasi-linear analysis of the extraordinary electron wave destabilized by runaway electrons
• Electromagnetic waves destabilized by runaway electrons in near-critical electric fields
• Alfvénic instabilities driven by runaways in fusion plasmas
• Numerical calculation of ion runaway distributions

Cited by in corpus (1)

• The impact of fusion-born alpha particles on runaway electron dynamics in ITER disruptions