Fabrication of YBCO Small Test Coils for Accelerator Magnet Development

Abstract

A research program for studying coil winding technologies using (YBCO) coated conductors is now in progress. In this program, we are attempting to develop highsuperconducting magnets for highly functional, efficient, and compact accelerator systems. In designing superconducting coils with thin tape conductors, we must be concerned about magnetization of the superconducting layer. In order to experimentally evaluate the influence of the additional field resulting from the magnetization current, prototype racetrack coils were constructed with YBCO coated conductors. A 62 m length of coated conductor was wound to form each of the coils, which were then impregnated with epoxy resin. For precise analysis of the additional magnetic field, it is essential to fabricate superconducting coils without degradation because the voltage generated at such a degraded part would affect the behavior of the additional magnetic field. In a liquid nitrogen environment, the racetrack coils were energized to evaluate the voltage-current (V-I) characteristics. It was found that there was no degradation in the superconductivity. The V-I characteristics showed sufficiently high index values of 28 and 34 throughout an electric field range of . Magnet design derived from accelerator design, as well as construction of an experimental reduced-scale coil in a typical shape, are also discussed.

Progress of Research and Development of Fundamental Technologies for Accelerator Magnets Using Coated Conductors

“…Coils must be impregnated with epoxy resin to improve thermal conductivity for conduction cooling by using cryocooler [26]. R&D of these technologies are carried out in our project [10], [13]. Target figures such as minimum bending radius of coated conductor, curvature to form three-dimensional coils, and the minimum radius of negative bend were set based on the specifications of the designed coils given in [12] and III.B.…”

R&D Efforts Towards High Field Accelerator Magnets at KEK

“…The winding procedure should be carefully considered because three-dimensional arrangement and deformation of the HTS tape may compromise the superconducting performance and the field quality [19], [20]. These issues a serious concern and some elemental studies have been already performed [17]- [21].…”