Characteristics of halo currents in JT-60U

Halo currents (I-h) and their toroidal peaking factors (TPFs) have been mea sured in JT-60U by Rogowski coil type halo current sensors. The maximum val ue of TPF x I-h/I-p0 was 0.52 in the operational range of I-p0 = 0.7-1.8 MA , B-T = 2.2-3.5 T, including ITER design parameters of kappa > 1.6 and q(95 ) = 3, which was lower than that of the maximum value of the ITER database (0.75). This value of TPF x I-h/I-p0 correlated with the driving forces of the halo currents generated by the vertical shift velocity of the plasma. T he magnitude of the halo currents tended to decrease with the increase in s tored energy just before the energy quench and with the line integrated ele ctron density at the time of maximum halo current. A termination technique in which the current channel remains stationary demonstrated bow to avoid h alo current generation. Strong pulsed gas puffing during vertical displacem ent events was effective in reducing the halo currents.