A serious damage can happen to the power cable manufactured from the high-temperature superconducting (HTS) tapes due to overcurrent conditions or because of technical errors during the cable assembling. To avoid the cable damage in any urgent case, a quick interruption of the transport current is necessary. Comprehensive understanding of the current cutoff time of the HTS tape is required to restart the operation of the power transmission line. In this paper, we applied 100-A transport current to BSCCO and YBCO tapes. After interrupting the current, we measured the magnetic field profiles of each HTS tape. We compare the magnetic field profiles for the fast and slow cuts of the current. The cutoff time is 0.15 ms for the fast cut and 100 s for the slow one. The current density profiles are obtained by solving the inverse problem. Our results show that the magnetic field profiles are quite different from each experimental condition and HTS tape, which are related to the hysteresis of HTS tape characteristics.Index Terms-Current measurement, magnetic field measurement, superconductor tapes.

The radial transport of tungsten ions in a fusion plasma of the HELIAS stellarator with five magnetic field periods is studied by means of a new numerical code. The code solves guiding center equations for test particles (tungsten ions) with the use of a Runge–Kutta integrating scheme. Coulomb scattering of the tungsten ions on the background plasma particles (electrons, deuterons and tritons) is simulated by means of a discretized collision operator based on the binomial distribution and presented in terms of pitch-angle scattering and energy slowing down and scattering. The coronal model is used to determine the mean charge state of the tungsten ion ensemble ⟨Z(Te, ne)⟩ as a function of background electron temperature and density. Two plasma configurations with and without ergodic confinement regions and both with finite plasma pressure of β = 3% are considered. The nonergodic configuration possesses closed nested magnetic surfaces throughout the entire confinement volume. The ergodic magnetic field configuration is represented through additional magnetic field perturbations. Comparative analysis of the radial transport is performed for a time interval greater by a factor of 15 than the energy confinement time τE = 1.62 s required for the HELIAS reactor. In spite of the fact that the tendency of impurities to penetrate towards the plasma core is observed in both cases, the stochastic scenario exhibits reduced inward impurity flux.

Possible fusion reactivity enhancement due to 3 He minority ICRF heating in D-3 He toroidal plasma is demonstrated in present numerical simulations. On this purpose the particle code based on test-particle approach is developed. This code solves guiding center equations for 3 He ions in toroidal magnetic field including Coulomb collisions of these ions with the background deuterons and electrons. A simple Monte Carlo model for ICRF heating is implemented in this code as well. The transformation of 3 He distribution function from Maxwellian to non-Maxwellian due to heating plays the key role for reactivity enhancement. The formation of significant energetic tail gives rise to the reactivity enhancement. This is an important issue for the performance of fusion reactors with minority heating of ICRF.

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