Improvement of Superconducting Linear Acceleration System for Pellet Injection: Optimization of Current Profile

The improvement of the acceleration performance of a superconducting linear acceleration (SLA) system for injecting the pellet container into the helical fusion reactor has been investigated numerically. To this end, a numerical code used in the finite element method and the non-dominated sorting genetic algorithms-II has been developed for analyzing both the shielding current density in an HTS film and the dynamic motion of the film. In addition, the current profile of the acceleration coil is optimized by the normalized Gaussian network (NGnet) method. The results of the computations show that when the current profile of the outer coil is optimized by using the NGnet method, the pellet velocity is greatly faster than that for the homogeneous current profile. Moreover, the speedup ratio decreases monotonously as the coil length increases. If the length of the outer coil is more than twice that of the inner coil, the number of the filaments outside the inner coil reduces extremely. This result means that the amount of the filament and the energy consumption can be reduced compared with the homogeneous current profile.