Coexistence of collisional drift and flute wave instabilities in bounded linear ECR plasma

This paper reports the experimental and theoretical investigation on the coexistence of the collisional drift and flute wave instabilities in the bounded linear electron cyclotron resonance (ECR) plasma. The drift wave instability is excited by the steep density gradient and imposed axial boundary conditions in the device. The flute instability is excited by the bad curvature of the magnetic field. Emphasis is made on the effect of the ion-neutral (i-n) particle collisions. It is observed that the drift wave instability is excited when the i-n particle collision frequency ν _in is low, but it is stabilized when ν _in is high. Furthermore, the drift and flute modes are coexistent for the intermediate values of ν _in. The Hasegawa-Wakatani model which describes the dispersion relation of the collisional drift-interchange mode is used for understanding the experimental observations. It is found that the experimentally observed drift frequency is consistent with the numerical calculation. The present result has shown that the i-n particle collisions play an important role in the stabilization of the collisional drift wave instability in the ECR plasma.