Current Distribution Optimization in Electromagnet: Application to Superconducting Linear Acceleration System

The current distribution in the electromagnet is optimized so as to maximize the acceleration performance of a superconducting linear acceleration (SLA) system. As a novel pellet injection system for a fusion reactor, the SLA system has been proposed recently. The SLA system is composed of the electromagnet and the pellet container to which a high-temperature superconducting (HTS) film is attached. The pellet container is accelerated by using the Lorentz force between the HTS film and the electromagnet. In the present study, the current distribution in the electromagnet is represented as a set of the filaments by the on-off method. Moreover, the current distribution optimization is performed by using the non-dominated sorting genetic algorithm II (NSGA-II). Furthermore, the dynamic motion of the pellet container is determined by solving the equivalent-circuit model and Newton’s equation of motion. According to the numerical results, the acceleration performance is improved by partly applying the electric current to the electromagnet. Compared with the case of the homogeneous current distribution, the pellet velocity for the optimized current distribution increases by 26%.

对电磁铁中的电流分布进行了优化，以使超导直线加速器（SLA）系统的加速性能最大化。作为一种用于核聚变反应堆的新型弹丸注入系统，SLA系统是近期被提出的。SLA系统由电磁铁和贴有高温超导（HTS）薄膜的弹丸容器组成。弹丸容器利用HTS薄膜和电磁铁之间的洛伦兹力来加速。在本研究中，通过开关法将电磁铁中的电流分布表示为一组细丝。此外，使用非支配排序遗传算法II（NSGA - II）进行电流分布优化。再者，通过求解等效电路模型和牛顿运动方程来确定弹丸容器的动态运动。根据数值结果，通过对电磁铁部分施加电流，加速性能得到了提高。与均匀电流分布的情况相比，优化电流分布下的弹丸速度提高了26%。