Abstract
In this paper, we report new results of a beam switching experiment aiming at a reversed magnetic shear profile formation for the study of an MHD-mode-induced profile collapse event. A transient MHD mode, whose oscillation frequency chirps down, is observed. The electron temperature profile collapse is induced by the mode activity, leading to the flattening of the central electron temperature profile. The radial mode structure is the double-odd-parity at the beginning, but it transits to the even-parity in its final stage. The central electron temperature profile recovers after the radial mode structure changes to the even-parity, even though the mode itself does not disappear.
Highlights
In order to produce a sufficiently high temperature plasma in fusion devices toward the reactor, it is crucially essential to understand the physics of the plasma profile formation
Much attention is paid to avoid these MHD events by various active control techniques [13]. In heliotron devices such as the Large Helical Device (LHD), there are generally no disruptions, investigations for the profile collapse events induced by the transient MHD modes can be safely performed
We report new results of a beam switching experiment aiming at a reversed magnetic shear profile formation for the study of an MHD mode induced profile collapse event
Summary
In order to produce a sufficiently high temperature plasma in fusion devices toward the reactor, it is crucially essential to understand the physics of the plasma profile formation. Much attention is paid to avoid these MHD events by various active control techniques [13] In heliotron devices such as the Large Helical Device (LHD), there are generally no disruptions, investigations for the profile collapse events induced by the transient MHD modes can be safely performed. The beam switching from the co-beam to the counter-beam enhances flattening of the rotational transform profile and even produces a reversed shear profile [14, 15] This operation was used for studying the static island formation in LHD, and it was revealed that the island property was highly sensitive to the local magnetic shear [16].
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