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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. Katsurai^1)
 
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 B_t.

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