(EX/P3-14) Spontaneous and Artificial Generation of Shear Flow in Oblate FRCs in TS-3 and 4 FRC Experiments

**Abstract.** Spontaneous formation of toroidal flow shear was identified for
the first time in oblate FRCs of TS-3 and 4 experiments. Their velocities
around 10 km/sec were found to peak around the magnetic axes. In high-s FRC
(averaged number of ion gyro-radius ``s''
4.5) with low velocity, its
n=1 mode kept growing, causing collapse of the whole configuration. However,
in low-s FRC (
s 3) with fast flow, the rotating n=2 mode became
dominant after n=1 mode saturation. The spontaneous formation of flow shear
possibly transformed the n=1 mode into the n=2 rotational mode, suggesting a
new flow-shear stabilization of n=1 mode. The forced generation of flow
shear was also demonstrated using the ``sling shot'' effect of the
counterhelicity reconnection. The n=1 and 2 mode amplitudes were reduced by
factor 5-10 due to the shear-flow. A new continuous generation of shear flow
is being demonstrated for the stabilization and heating of FRC by use of
multiple (more than two) merging of spheromaks with opposing B_{t}.

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*IAEA 2003*