The plasma current decay time during the initial phase of the radiation induced disruption in JT-60U tokamak is studied based on the plasma inductance and resistance estimated by experimental data. The plasma resistance is estimated from the electron temperature profile measured by ECE (Electron Cyclotron Emission) diagnostic systems and the measurement of He I line emission intensity ratios and the plasma inductance is calculated by CCS (Cauchy-Condition Surface) method using magnetic sensor

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... gnals. We analyze 9 disruptive plasma shots with massive neon gas puffing. From the measurement results, the area-normalized current decay time derived from the L/R model, which is used for design of ITER (International Thermonuclear Experimental Reactor), is not dependent on the electron temperature, and experimental decay time is one order of magnitude smaller than the L/R time in short experimental decay time region (15 ~ 30 ms). On the other hand, a new prediction decay time, which is taking the time evolution of the plasma inductance into account, is considerably consistent with the experimental decay time. Therefore, in the radiation induced disruption plasmas, it is found that the time change rate of the plasma inductance during the current quench is an important parameter in short decay time region to precise predict the current decay time.