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

T. Matsuyama1), E. Kawamori1), Y. Ono1), M. Tsuruda1), K. Sato1), T. Yamanoue1), K. Arimoto1), T. Itagaki1), M. Katsurai1)
1) Department of Electrical Engineering, University of Tokyo, Tokyo, Japan

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'' $ \sim$ 4.5) with low velocity, its n=1 mode kept growing, causing collapse of the whole configuration. However, in low-s FRC ( s $ \sim$ 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 Bt.

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IAEA 2003