JOREK simulations of edge-localized mode effects on heat load and target erosion in the EHL-2 spherical torus

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Abstract This study utilizes the nonlinear magnetohydrodynamic code JOREK to investigate edge-localized mode (ELM) dynamics in the EHL-2 spherical torus, which is a device specifically designed for p- 11 B fusion. It investigates the nonlinear evolutions of multimode ELMs, as well as their impact on divertor heat loads and target erosion. Nonlinear simulations that incorporate toroidal modes ranging from n = 2 to 20 unveil a mode transition process. Although linear analysis designates n = 18 as the most unstable mode, the nonlinear interactions generate the n = 16 mode, thus becoming dominant during the crash phase. The ELM crash triggers stochastic magnetic fields, enhances cross-field transport, and causes the pedestal pressure to decrease by approximately 20%. Moreover, around 0.1 MJ of energy (10% of the total pedestal energy) is released into the scrape-off layer because of this crash. This phenomenon results in a significant heat flux that peaks at ~ 80 MW·m −2 on the outboard divertor targets. Furthermore, the simulation result demonstrates that the physical sputtering dominates carbon erosion, with the peak erosion flux reaching 6.5×10 21 m −2 ·s −1 . These findings highlight severe challenges for plasma-facing components and underscore the urgency of developing effective ELM control schemes for sustainable p- 11 B operation in EHL-2.

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