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ISSN: 2772-8307
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cited:8
Heavy ion irradiation effects on the high-frequency properties of YBCO and Nb3Sn thin films
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Article Number:Article 100149
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Abstract
Corresponding email:gianluca.ghigo@polito.it
High-energy heavy-ion irradiation is known to produce effective vortex pinning centers in the high- cuprate superconductors, as amorphous columnar tracks. However, while the beneficial effects on pinning has been well established through dc and low-frequency characterizations, the same analysis in the high-frequency regime is far from complete. Even less investigated are the effects of heavy ion irradiation on the microwave properties of metallic low- superconducting films. Here, we report on the effects of 1.15 GeV Pb irradiation on the high frequency properties of YBaCuO (YBCO) and NbSn thin films. The microwave analysis, performed in the range 7-8 GHz, allows obtaining the fundamental properties of both the materials, as the London penetration depth and gap values, and of the main pinning parameters, through the determination of the Campbell length by measurements in dc magnetic fields up to 4 T. GeV heavy-ion irradiation confirmed to be extremely effective for YBCO also in the high frequency regime, enhancing both the pinning constant and the depinning frequency, thus pushing the critical current density to about 30% of the depairing current density. On the other hand, the discontinuous but correlated defects produced in NbSn was found to be ineffective to enhance the pinning properties (the pinning constant in fact decreases), while the observed increment of the depinning frequency is ascribed to the reduction of the vortex viscosity, in turn due to the growth of the normal state resistivity.
cited:1
The superconducting magnet development for the next generation ECR ion source on LEAF
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Article Number:Article 100151
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Corresponding email:sunlt@impcas.ac.cn; zhaohw@impcas.ac.c
In December 2024, the world first stand-alone Low Energy high intensity heave ion Accelerator Facility (LEAF) has been commissioned to its design performance and passed the acceptance test conducted by the National Natural Science Foundation of China. LEAF is designed and built by the Institute of Modern Physics, CAS, which is aiming to provide unprecedent ion beam conditions for the researches of nuclear astrophysics, atomic physics, nuclear materials and so on. To realize this goal, it is essential to develop an ECR (Electron Cyclotron Resonance) ion source beyond the performance of the state-of-the-art machines. This ECR ion source is called FECR (First 4th generation ECR ion source) designed to be operated with the plasma heated by 45 GHz microwave frequency that needs high magnetic field confinement. Therefore, with FECR Nb3Sn superconducting technology was incorporated to ECR ion source for the first time in the world. FECR features Nb3Sn solenoids and NbTi sextupole coils that enables its high performing operation at 45 + 28 GHz microwave heating.
cited:6
Impact of distributed Bragg reflectors on the intrinsic detection efficiency of superconducting nanowire single-photon detectors
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Article Number:Article 100152
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Corresponding email:lihao@mail.sim.ac.cn
In this study, we investigate the impact of substrates with distributed Bragg reflectors (DBRs) on the proximity effect during the fabrication of superconducting nanowire single-photon detectors (SNSPDs) using electron beam lithography. We compare the linewidth compression and line edge roughness of nanowires prepared on three different DBRs substrates. Additionally, we characterize the variations in switching current (I) and intrinsic detection efficiency (IDE) at a 2.2-K temperature. The results show that when the substrates are composed of low atomic number materials, such as Si and SiO2, the proximity effect is significantly mitigated. As a consequence, the lithography quality of nanowires is effectively improved, thus enhancing the IDE of SNSPDs. This study is expected to provide new insights into the fabrication of SNSPDs and lay the foundation for the preparation of high-performance and high-uniformity large-area devices.
cited:10
Evolution of superconductivity and corresponding electronic structure in pressurized Nb3Sn
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Article Number:Article 100153
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Abstract
Corresponding email:duandf@jlu.edu.cn; jguo@iphy.ac.c
The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications. Nb3Sn, an intermetallic alloy with an A15 structure, is a key commercial superconductor known for its high critical current and magnetic field tolerance. Here, we systematically investigated the physical properties of Nb3Sn under high pressures. Our findings reveal that superconductivity in Nb3Sn remains robust up to 142 GPa, demonstrating remarkable stability despite a gradual suppression of with increasing pressure. First-principles calculations indicate that the pressure-dependent superconducting behavior is primarily driven by variations in the density of states of Nb’s d-electrons, particularly contributions from the and orbitals. Furthermore, we predict the potential for synthesizing Nb3Sn films and demonstrate that biaxial strain induced by suitable substrates can preserve their superconducting properties. This comprehensive study not only enhances our understanding of Nb3Sn’s superconducting mechanism under high pressure but also opens new avenues for its application in advanced superconducting technologies.
cited:2
Microstructural evolution mechanism of Ba0.6KαFe2As2 Cu/Ag composite sheathed superconducting tapes
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Article Number:Article 100154
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Abstract
Corresponding email:ywma@mail.iee.ac.cn
Low-cost Cu/Ag composite sheathed BaKFe2As2 superconducting tapes have been the focus of considerable research interest in terms of superconducting properties and performance improvement. The K-doping content has a great influence on the transport critical current density () of Cu/Ag composite sheathed tapes. This study analyzes the evolution occurring within the micro-composition and the mechanism affecting the transport in BaKFe2As2 (0.42 0.54) raw material, by modulating the ratio of K. It has been demonstrated that both extremes of K content, namely an insufficient or excessive amount, have an adverse effect on phase purity of the powders. Consequently, this has a direct impact on the transport of tapes. Cu/Ag tapes fabricated using a precursor powder with an optimal K ratio 0.464 exhibited the highest performance, with a of 5.8 × 104 A cm −2 at 10 T and 4.2 K. The optimized Cu/Ag composite tapes have been found to have superior advantages for high-field applications.
cited:9
Mechanical and electromagnetic characteristics of MgB2 wires & Cable-in-Conduit Conductors for fusion magnet application
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Article Number:Article 100155
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Abstract
Corresponding email:chao.zhou@ipp.ac.cn
A study on a 4-stage sub-size MgB2 Cable-in-Conduit Conductor (CICC), tested at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), revealed a 20% degradation in critical current at 4.2 K compared to single-strand data. To address this issue, the mechanical properties of MgB2 wires from Hyper Tech and WST were investigated, and two sub-size CICCs were manufactured using a “close-to-1-ratio” Twente design with smaller diameter wires. These cables demonstrated no significant degradation in critical current after cabling and compaction, nor after electromagnetic load cycling. The results indicate that the close-to-1-ratio cable design is optimal for brittle superconducting materials such as MgB2, Nb3Sn, and BSCCO, as it minimizes mechanical stress and preserves superconducting properties. This design shows significant potential for the application of MgB2 in next-generation fusion reactors, particularly in Poloidal Field (PF) coils, Correction Coils (CC), and feeders.
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