Numerical Investigation on Superconducting Linear Acceleration System for Pellet Injection by Using Equivalent-Circuit Model

Plasma and Fusion Research

Kamitani

et al. 2020

Self Cite

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%.

Section: Governing Equationmentioning

confidence: 99%

“…In order to clarify the acceleration performance, we simulated the dynamic motion of the container accelerated by the multiple-electromagnet SLA system. As a result of the SLA simulation [3], it was clear that the pellet velocity can reach up to 5 km/s. However, a considerable number of the electromagnets must be placed over 40 km.…”

Section: Introductionmentioning

confidence: 97%

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

Plasma and Fusion Research

Kamitani

et al. 2020

Self Cite

“…In the previous study, the authors proposed the Equivalent-Circuit Model (ECM) to analyze a shielding current density in an axisymmetric HTS film [5,6]. By using the ECM, they numerically investigated the acceleration performance of the SLA system for the multiple electromagnets.…”

Section: Introductionmentioning

confidence: 99%

“…By using the ECM, they numerically investigated the acceleration performance of the SLA system for the multiple electromagnets. As a result, it was found that a considerable number of the electromagnets must be placed over 40 km to increase the pellet velocity up to 5 km/s [6]. Accordingly, it is essential to improve the acceleration performance of each electromagnet.…”

Section: Introductionmentioning

confidence: 99%

Current Distribution Optimization by Using Genetic-Algorithm Based On-Off Method: Application to Pellet Injection System

Ohtani

et al. 2020

JASSE

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The current distribution in the electromagnet is optimized by using the geneticalgorithm based on-off method so as to maximize the acceleration performance of the Superconducting Linear Acceleration (SLA) system. In the SLA system, a pellet container is accelerated by the interaction between a shielding current density and an applied magnetic field. By using the equivalent-circuit model, the distribution of the shielding current density is approximated as a set of the multiple current loops. In contrast, the current distribution in the electromagnet is represented by means of the on-off method. As the method for optimizing the current distribution in the electromagnet, two types of genetic algorithms are adopted. The results of computations show that the pellet velocity for the optimized current distribution is 1.3 times as fast as that for the homogeneous current distribution.

“…On the other hand, a superconducting linear acceleration (SLA) system [4], [5] has been recently proposed as an alternative pellet injection system for the fusion reactor. The pellet is accelerated by the Lorentz force acting on the ringshaped HTS film, and the SLA system can inject it into the core plasma.…”

Section: Introductionmentioning

confidence: 99%

Equivalent-Circuit Model for Axisymmetric High-Temperature Superconducting Film: Application to Contactless j_C Measurement System and Pellet Injection System

2019 22nd International Conference on the Computation of Electromagnetic Fields (COMPUMAG)

Kamitani

et al. 2019

Self Cite

By using an equivalent-circuit model, a shielding current density in an axisymmetric high-temperature superconducting (HTS) film can be analyzed. In the present study, this model is applied to a permanent magnet method, inductive method, and pellet injection system in order to investigate their performance. As a result, it became clear that the inductive method can estimate a critical current density with an error less than 7%. Moreover, the permanent magnet method can be applied to the HTS film having a critical current density from 0.1 MA/cm 2 to 10 MA/cm 2 . The numerical result also shows that a mass of HTS film can be reduced to about 40% without deteriorating an acceleration performance of the pellet injection system.