Joonsun Kang

Comparison of shape and topology optimization methods for HTS solenoid design

This paper compares the advantages and shortcomings of shape optimization method and topology optimization method for HTS solenoid design. For both methods critical current condition of superconducting material is taken into account for accurate analysis and design. Details of each method are explained including design variables and sensitivity analysis. With these methods, it is possible to design HTS solenoid that makes efficient use of superconducting material. Design results show that it is best to use topology optimization method for basic layout design and use shape optimization method for the fine-tuning of the basic layout.

Magnet Design of the Superconducting Cyclotron for Carbon Therapy

Korea Institute of Radiological & Medical Sciences (KIRAMS) has started the development of a superconducting cyclotron for carbon therapy. The goal of the development is to produce a 430 MeV/u carbon beam for medical use. The magnet system is composed of one set of NbTi superconducting coils and four spiral sectors with a return yoke. The hill angular widths, hill gaps, and spiral angles with radius have been designed for the isochronous magnetic field. The spiral sector shape and the beam characteristics of the designed magnetic field have been presented.

Design Study of a K22 Prototype Superconducting Cyclotron Magnet

Korea Institute of Radiological & Medical Sciences (KIRAMS) has been developing a superconducting cyclotron since 2007. This paper is concentrated on the design of the superconducting magnet system. The superconducting magnet for a cyclotron consists of an iron yoke and a superconducting coil system. This paper presents the designed spiral sector for beam stability and the design results of the superconducting coil system. Additional test results of the superconducting coils are described.

Radial magnetic field reduction to improve critical current of HTS solenoid

Abstract To enhance the critical current of superconducting coil, the magnetic field experienced by superconductor strand (tape) in a coil should be minimized. This is true for both low T c and high T c superconductors, and the difference between the two lies in their isotropic/anisotropic characteristics. In this paper, we propose a shape optimization algorithm to reduce radial magnetic field components in HTS solenoid to enhance critical current of a solenoid. In the algorithm, the finite element method and the continuum shape design sensitivity formula were employed. The objective function is to minimize the maximum radial magnetic fields in a solenoid with a constraint of constant solenoid volume condition. In this paper, the details on algorithm are introduced and the calculated optimized shapes are presented.

Maximization of flux-linkage in HTS motors using shape design sensitivity analysis with critical current constraint

This paper proposes a design method for optimizing the rotor winding shape of HTS motor. The design objective is to maximize the flux-linkage of stator winding with a given amount of superconductor volume. The increase of flux-linkage results in output-power increase, compact size and quench-reliable characteristic. The optimization algorithm is a design sensitivity analysis where the HTS critical current condition is taken into account. First, the shape of rotor winding is optimized to give a boundary shape of smooth curves. Second, with the shape the rectangular sizes of windings are approximately obtained for easy manufacture. Finally, the rectangular sizes are also optimized for fine-size tuning. The proposed design method is applied to the 100-hp HTS motor.

Topology optimization method for superconducting system with critical current condition

A new design scheme is developed to use the topology optimization method in the superconducting system. The critical current condition is considered in the sensitivity calculation for accurate analysis and design of the system. The density method is used to model the design space, and the normalized density of superconducting filament in each cell is used as design variables. The designs of SMES (superconducting magnetic energy storage) coil and MRI (magnetic resonance imaging) coil are given as numerical examples.

Numerical calculation of critical current in Bi-2223 stacked tapes

As we stack HTS tapes, the critical current of stacked tapes is much less than the total summation of the critical current of each tape. This is mainly due to self magnetic field effects, and its behavior has been analyzed by load line or numerical methods with some assumptions. In this paper, we propose a simple numerical model to calculate the critical current of stacked tapes more exactly. To do this, we measured J/sub c/-B curves of a HTS tape for various values of external magnetic fields and the angles between the magnetic field and the tape surface. Using this experimental data, the current density distribution in the cross section of stacked tapes is calculated numerically and the results are compared to both experimental values and the ones from load line analysis method, calculated simply by assuming uniform current density across the tapes.

Critical current evaluation of BSCCO stacked tapes

Abstract Critical current of HTS stacked tapes is usually much smaller than the total summation of all critical currents of the tapes. This is mainly due to the self-magnetic field, and so far its behavior has been modeled by assuming constant current density distribution across the tape or by a numerical method with an assumption of J c which is dependent on the normal magnetic field to the tape surface but independent of parallel magnetic field. To predict the critical current of the BSCCO stacked tapes more exactly, it is necessary to calculate the critical current distribution across the stacked tapes. Since the critical current distribution across a tape is highly dependent on the strength and incident angles of magnetic field, which is the sum of external and self-magnetic fields, we need to rely on numerical analysis to get correct answers. We used a numerical model to calculate the critical current of stacked tapes. For this purpose we measured J c – B curves of a BSCCO tape for various incident angles between the magnetic field and tape surface. Using this experimental data, the critical current distribution across the stacked tapes was calculated for different stacking shapes. In this paper, the calculated critical currents are compared with the experimental data for one to five stacked tapes to prove the validness of the model, and we analyze the critical currents for various stacking configurations.

Design Study of Main Dipole Magnets for Korea Heavy Ion Medical Accelerator Synchrotron

The Korea Institute of Radiological and Medical Science launched a project to construct an accelerator facility for carbon ion therapy, known as the Korea Heavy Ion Medical Accelerator (KHIMA), in April 2011. The development of the synchrotron for this facility began in 2014, and its main dipole magnets are currently in the design phase. In the study described herein, a simulation model of a main dipole magnet was created based on the Proton-Ion Medical Machine Study, and the basic parameters of the dipole magnets and their magnetic field requirements were investigated. The coil specifications were considered, and the pole profile was optimized to achieve the necessary magnetic field quality. Furthermore, the dynamic behavior of the modeled magnet was studied to estimate the effects of the eddy current and the driving voltage. The results of this design study are presented in this paper.

HTS motor shape optimization for its maximum critical current of the field winding

Superconducting motors have high efficiency as well as reduced size and weight. In superconducting motors, the field winding is composed of HTS tapes (Bi-2223) without any iron core because of magnetic saturation, and the current in the field winding is limited by the maximum magnetic field in the field winding. To enhance the performance of superconducting motor, we need to maximize the critical current of field winding as much as possible. This paper introduces the shape optimization method with the constraint of HTS characteristic (I/sub c/-B curve), and proposes a shape that improves the critical current of the field winding. Finite element analysis and discrete sensitivity approach are used for calculating the magnetic field of coil and shape optimization.