The avalanche type of transport can induce a long-radial transport and thus can contribute to the global profile formation. In this study, we observed the heat perturbations exhibiting avalanche-like transport in the stellarator/heliotron device, Heliotron J, and the tokamak device, JT-60U. We found that the electron heat propagation in Heliotron J is mainly generated from the heating source region. The relatively high value of the Hurst exponent, which is a signature of avalanches, depends on the total heating power. On the other hand, the electron and ion heat avalanches measured in JT-60U tend to spread from the local peak of the temperature gradient and are not influenced by the heating source profiles. The contrasting features of avalanches in stellarator/heliotrons and tokamaks potentially imply the difference in the temperature profile formation, such as the presence of stiffness.
This paper investigates the 'avalanche-like' transport of heat in fusion plasma devices, where heat perturbations can spread rapidly across the plasma. The authors observed this phenomenon in the Heliotron J stellarator and the JT-60U tokamak, finding differences in the heat propagation patterns between the two devices. This provides insights into how the temperature profile is formed in these fusion reactors.