Quasicontinuous Exhaust Scenario for a Fusion Reactor: The Renaissance of Small Edge Localized Modes

Area of Science:

• Plasma physics
• Fusion energy research

Background:

• Tokamak reactors face challenges with transient heat loads caused by large edge localized modes (ELMs).
• Small ELMs are proposed as a potential solution to mitigate these heat loads.
• Ballooning modes near the last closed flux surface, influenced by pressure gradients and magnetic shear, are hypothesized to cause small ELMs.

Purpose of the Study:

• To experimentally investigate stabilizing effects near the last closed flux surface.
• To connect linear ideal simulations with nonlinear resistive simulations for small ELMs.
• To validate the suitability of the small ELM regime for future fusion reactors.

Main Methods:

• Experimental investigation of stabilizing effects near the last closed flux surface.
• Linear ideal magnetohydrodynamic (MHD) simulations to identify ballooning-like fluctuations.
• Nonlinear resistive simulations to model ELM behavior.

Main Results:

• Stabilizing effects near the last closed flux surface were experimentally investigated.
• Linear ideal simulations confirmed the development of ballooning-like fluctuations.
• These fluctuations were successfully linked to nonlinear resistive simulations.
• The dimensionless parameters of the small ELM regime closely match those of a reactor.

Conclusions:

• Small edge localized modes (ELMs) in tokamaks are a promising solution for managing transient heat loads.
• The investigated regime, characterized by ballooning-like fluctuations, exhibits parameters suitable for future fusion reactor designs.
• This research supports the small ELM regime as an ideal exhaust scenario for next-generation fusion devices.