A curvaturehyphen;driven flute instability will be excited in the magnetized plasmas if the magnetic field lines curve toward the entire plasma boundary. Conditions under which it can be effectively stabilized in axisymmetric geometry have been experimentally studied in a gashyphen;dynamic trap (GDT) at Novosibirsk. Flexible design of the experimental device and the availability of neutral beams and ion cyclotron heating enabled the pressurehyphen;weighted curvature to be varied over a wide range. The stability limits were thus measured and compared with those predicted by the modified Rosenbluthndash;Longmire criterion. Characteristics of unstable curvaturehyphen;driven flute modes were also measured and found to conform to a theory including finite ion Larmor radius (FLR) effects. Stable operation during neutral beam injection was achieved with a cusp end cell, resulting in an increase inTeto 45 eV, limited by end losses rather than anomalous power losses. thinsp;
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