Internal magnetic field measurements using the transient internal probe on the helicity injected tokamak

Summary for only given, as follows. The transient internal probe (TIP) uses a high velocity (2 km/s) magneto-optic probe to measure internal magnetic fields in hot plasmas. TIP has both accurately (2%) measured the internal toroidal field profile and directly measured internal magnetic fluctuation levels of the helicity injected tokamak (HIT). HIT is a low-aspect-ratio (A=1.5) spherical tokamak designed to investigate steady state current drive using coaxial helicity injection. Operating parameters are T/sub e//spl sime/100 eV, n/sub e//spl sime/5/spl times/10/sup 13/ cm/sup -3/ and I/sub p/=250 kA. These tokamaks are characterized by a 30-70 kHz rotating n=1 magnetic distortion. Measurements using TIP confirm that this n=1 mode is present only on the outer edge of the plasma in the bad-curvature region. Fluctuation levels of 150 G in the vicinity of the separatrix dramatically decrease in the core of the plasma.