Transient Appearance of Double Spontaneous-Snakes in EAST H Mode Plasma

Transient lasting of double spontaneous snakes is observed in energy confinement improved plasma on the EAST tokamak. The destabilization of snakes with superb particle confinement can lower plasma energy confinement and slow plasma toroidal rotation. The non-monotonic q profile with double q=1 surface, slightly above unity in central, is constructed. The prevailing harmonic modes are susceptible to the nearly zero magnetic shear. Finally, the role of anomalous particle transport and the formation of off-axis peaking electron profile on the excitation of double snakes are discussed.