Abstract
High-temperature superconductors (HTS) are materials that hold great promise for future particle-accelerator plants. YBa2Cu3O7-x-based (YBCO) second-generation coated conductor coils can produce the intense field needed for ion confinement. Such coils can act as a radiation resistance magnet when exposed to radiation, and therefore, it is essential to better understand irradiation responses and defect creation in YBCO superconductors. The influence of laser or ion irradiation on the electrical characteristics of HTS has been studied previously; however, most results remain ambiguous and inconsistent. Degradation of or incremental changes in the critical current of the HTS tap are currently only observed and explained via irradiation dose. The relation between irradiation defects and macro-multi-field responses has yet to be established for YBCO tapes, for magnet design and operation. In this study, YBCO (2 G HTS) taps with Ag, Cu–Ag, and Cu protective cap layers were selected as targets of Nd-laser irradiation, at varying power. Irradiation defects were formed in YBCO taps, and irradiation dose was monitored as a function of superconducting properties and mechanical behaviors. The critical current and its N-values eventually degrade under intense Nd-laser irradiation, and the mechanical behavior of YBCO tapes shows nonlinear features after irradiation. Scanning electron microscopy and x-ray energy-dispersive spectrometry were applied to investigate the micro-defect changes that occurred in the taps after each Nd-laser irradiation dose. Micro-structural observations showed that the protective layers were critical for radiation resistance in YBCO taps. Furthermore, the macro-stress dependence of the critical current field was measured before and after Nd-laser irradiation to establish the relationship with micro-defect morphology by Nd-laser irradiation.
Highlights
HIAF (High Intensity heavy ion Accelerator Facility), a new international project, has been proposed by IMP (Institute of Modern Physics, Chinese Academy of Sciences) for heavy-ion related research
YBCO taps with different protective layers were used in our study: SCS12050-AP tape with a 20-μm Cu cap layer and a width of 12 mm, SF12050-AP tape with an 8-μm Ag cap layer and a width of 12 mm, and SF6050-AP tape with a 20-μm Cu–Ag cap layer and a width of 6 mm
We showed that the applied energy of the Nd-laser resulted in decreases in the critical current and its n-values and that the mechanical behavior of YBCO tapes possessed nonlinear features after laser irradiation
Summary
HIAF (High Intensity heavy ion Accelerator Facility), a new international project, has been proposed by IMP (Institute of Modern Physics, Chinese Academy of Sciences) for heavy-ion related research. Laser interaction that mainly produces heat effects is completely different from neutron or other ions irradiation effect, under such thermal conditions, the surface is still expected to experience the non-equilibrium state, obtaining new functional properties, the surface of oxide material may contain many pores, micro-cracks, insulating phases, and impurities at the grain boundaries that will modify the sample’s critical current density. Luctiv et al. studied the effect of different kinds of laser (Nd, CO2, and ruby) irradiation on 123-YBCO, Bi-2212, and Bi-2223 and found an enhancement in critical current density Jc but a suppression of Tc because the fraction volume of diamagnetism inside the bulk superconducting sample decreased. We explore the effects of Nd-laser irradiation on the superconducting properties, microstructure, and macrostress dependence of the critical-current field of YBCO taps. This study examines these phenomena by comparing the effects of laser irradiation on tapes
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