Abstract
The dynamic behaviour of the ion and electron energy, particle and momentum transport measured during type-I edge localized mode (ELM) cycles at ASDEX Upgrade is presented. Fast measurements of the ion and electron temperature profiles revelead that the ion and electron energy transport recover on different timescales, with the electrons recovering on a slower timescale (Cavedon et al 2017 Plasma Phys. Control. Fusion 59 105007). The dominant mechanism for the additional energy transport in the electron channel that could cause the delay in the electron temperature gradient () recovery is attributed to the depletion of energy caused by the ELM. The local sources and sinks for the electron channel in the steep gradient region are much smaller compared to the energy flux arriving from the pedestal top, indicating that the core plasma may dictate the local dynamics of the recovery during the ELM cycle. A model for the edge momentum transport based on toroidal torque balance that takes into account the existence of poloidal impurity asymmetries has been developed. The analysis of the profile evolution during the ELM cycle shows that the model captures the dynamics of the rotation both before the ELM crash and during the recovery phase.
Highlights
Edge localized modes (ELMs) [1,2,3] are inherent to highconfinement mode (H-mode) plasmas, which are characterized by an edge transport barrier
The dominant mechanism for the additional energy transport in the electron channel that could cause the delay in the electron temperature gradient ( Te) recovery is attributed to the depletion of energy caused by the ELM
This paper extends our previous work [30,31,32] to the combined analysis of the ion and electron heat transport, as well as the behaviour of the momentum transport during the ELM cycle
Summary
Edge localized modes (ELMs) [1,2,3] are inherent to highconfinement mode (H-mode) plasmas, which are characterized by an edge transport barrier. ELMs cause detrimental heat and particle fluxes which pose a threat for the lifetime of the plasma facing components and lead to a quasi-periodic degradation of the pedestal. Besides the global peeling-ballooning mode that has an effect on the entire pedestal structure, the presence of local modes can affect the plasma edge in a very narrow region [9, 10], causing transport and leading to a change of the pedestal structure locally [11,12,13]. Understanding the physics behind ELMs and the effect they cause on particle, energy and momentum transport is important for a predictive capability of future fusion devices as the anticipated transient heat and particle fluxes associated with unmitigated ELMs are expected to severely limit the lifetime of plasma facing components.
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