Study of Energetic Ion Driven Instability using Twin Heavy IonBeam Probe on Compact Helical System

Energetic ion driven instabilities are concerned and extensively studied for the era of burning plasma in a number of tokamaks and stellarators since the instabilities can cause destabilization and degradation of the plasma performance and the resultant loss of energetic ions interacted with the instabilities can damage the vessel wall of the reactor. In Compact Helical System (CHS), we have investigated the energetic ion driven instabilities such as fishbone and Alfven modes, using twin heavy ion beam probes (HIBPs). Recently, we have succeeded in reconstructing the nonlinear evolution of the internal structure of CHS fishbone, an oscillatory state caused by the interaction between energetic ions and an MHD mode (m/n=2/1). In this presentation we mainly report the HIBP observations of CHS fishbone in terms of density and potential. The discovery of the zonal flow structure induced by the energetic ion loss during a cycle of CHS-fishbone is highlighted.