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(EXP3/11) Characteristics of Halo Current in JT-60U

Y. Neyatani, Y. Nakamura, R. Yoshino, T. Hatae and the JT-60 Team

Naka Fusion Research Establishment, Japan Atomic Energy Research Institute Mukoyama 801-1, Naka-mach, Naka-gun, Ibaraki-ken, 311-01, Japan

Abstract.  Halo currents and their toroidal peaking factor (TPF) have been measured in JT-60U by Rogowski coil type halo current sensors. The electron temperature in the halo region was around 10 eV at 1 ms before the timing of the maximum halo current. The maximum TPF *I_h/I_p0 was 0.52 in the operational range of I_p = 0.7 $\sim$ 1.8MA, B_T = 2.2 $\sim$ 3.5T, including ITER design parameters of $\kappa$ > 1.6 and q₉₅ = 3, which was lower than that of the maximum value of ITER data base (0.75). The magnitude of halo currents tended to decrease with the increase in stored energy just before the energy quench and with the line integrated electron density at the time of the maximum halo current. A termination technique in which the current channel remains stationary was useful to avoid halo current generation. Intense neon gas puffing during the VDE was effective for reducing the halo currents.

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