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Description
Understanding the dynamics of Energetic Particles (EPs) is essential for optimizing the perfor- mance of fusion devices. EPs serve as the primary energy carriers in fusion plasmas, and their loss due to transport from the core to the edge results in a significant reduction in efficiency of the fusion device. One of the key phenomena driving the EPs transport is the precessional fishbone instability[1].
The precessional fishbone instability is a kinetic instability driven by the destabilization of a magnetohydrodynamic (MHD) mode due to an EP gradient [2].
In this work, we present a numerical study of the precessional fishbone instability using a sim- plified 2D phase-space model [3]. The model couples a reduced MHD framework in cylindrical geometry, which describes the thermal plasma, with a kinetic description of trapped energetic particles. This study builds on the reduced MHD code AMON [4], to which we have added a gyro- and bounce-averaged Vlasov equation for the EPs.
We investigate the resonant interaction between particles and fields, which drives the nonlinear evolution of the EPs gradient, leading to their transport [5]. The question addressed in this study concerns the impact of MHD nonlinearities on the saturation level and the evolution of the mode frequency. While the linear phase of the fishbone instability is relatively well understood [3, 6], our work aims to investigate how MHD nonlinearities influence the level of saturation by preserving the resonant condition thus modifying the frequency chirping behavior [5], which are directly linked to the nature of EPs transport [7].
[1] R.B. White, et al., Physical review letters 62, 539 (1989)
[2] L. Chen, et al., Physics of Plasmas 7, 1519-1522 (1994)
[3] M. Idouakass, et al., Physics of Plasmas 23, 102113 (2016)
[4] A. Poye, et al., Plasmas Physics and Controlled Fusion 56, 125005 (2014) [5] L. Chen, et al., Reviews of Modern Physics 88, 015008 (2016)
[6] A. Fasoli, et al., Nuclear Fusion 47, S264 (2007) [7] F. Zonca, et al., Nuclear Fusion 45, 477 (2005)
