We perform a systematic study of the fermionic DM absorption interactions on electron target in the context of effective field theory. The fermionic DM absorption is not just sensitive to sub-MeV DM with efficient energy release, but also gives a unique signature with clear peak in the electron recoil spectrum whose shape is largely determined by the atomic effects. Fitting with the Xenon1T and PandaX-II data prefers DM mass at m_χ = 59 keV and 105 keV, respectively, while the cut-off scale is probed up to around 1 TeV. The DM overproduction in the early Universe, the invisible decay effect on the cosmological evolution, and the visible decay signal collected by the astrophysical X(gamma)-ray observations (Insight-HXMT, NuSTAR, HEAO-1, and INTEGRAL) are thoroughly explored to constrain the DM absorption interactions. With stringent bounds on the tensor and pseudo-scalar operators, the other fermionic DM operators are of particular interest at tonne-scale direct detection experiments such as PandaX-4T, XENONnT, and LZ.

The unique structure of conductors on round core (CORC) cable leads to symmetrical electromagnetic properties and excellent mechanical performance. However, it is quite a big challenge to analyze the mechanical properties of CORC cables, due to the unpredictable initial residual stress generated during the fabrication process of both tape and cable. In this paper, the mechanical model of CORC cable consists of several individual models representing the tape fabrication, cable fabrication, CORC cable bending and cooling process. The numerical model is verified by experimental results of both superconducting tapes and CORC cables. On basis of this, the numerical model is used to explain the mechanism of performance degradation during bending process. Moreover, the effects of winding angle on critical bending diameter are analyzed from the aspect of critical current degradation and physical extrusion. And simulation results are used to determine the principle critical bending diameter of CORC cable. Conclusions in this paper can be useful for design of CORC cables in applications where small bending diameter is needed.

High temperature superconducting (HTS) conductor on round core (CORC) cable is considered as a potential technology for power applications, because of its high current-carrying capacity, compactness, and strong mechanical properties. As the main component of CORC cable, center core is used to support the HTS conductors. However, for metal center core, eddy current induced in the core under alternating electromagnetic field is unneglectable, which will lead to extra AC loss in power applications. This paper focuses on the selection of center core of CORC cable. AC losses of CORC cable using different core materials are evaluated by both numerical and experimental methods, in which copper, stainless steel, fiberglass epoxy and nickel have been chosen as the core. Results illustrate that AC loss of CORC cable has a correspondingly increase with the conductivity of core material. Significant frequency dependence of AC loss indicates that for single layer CORC cable, proper core material should be chosen to minimize the eddy current loss. Besides, CORC cable with core of nickel shows a quite different AC performance due to its ferromagnetic characteristics. Conclusions obtained from this paper will provide essential data for future optimization on the design of CORC cables.

This paper presents the design of an HTS magnet for an ultra compact MRI system, potentially for the rapid and early diagnosis of brain trauma. Early diagnosis and therapy stratification can reduce the risk for critically brain ill patients with the use of near patient imaging, and can aid with precision medicine. High temperature superconductors (HTS) have the ability to carry large currents in the cryogen free contrition, which can make the MRI system even smaller and lighter. The design and Genetic Algorithm (GA) optimization were based on the FEM package COMSOL Multiphysics with the LiveLink for MATLAB, together with the GA module in the MATLAB optimization toolbox. The relatively thick HTS tape, ST-12-L from the Shanghai Superconductor Technology was chosen and that made more difficulty on optimization process. Genetic Algorithm method improved the optimization performance, and the uniformity achieved 2.36 ppm in a 10 × 10 × 10 cm DSV. Two cases of the end double-pancake were compared. Further sensitivity studies were performed on the homogeneity with its relationship to the magnet length, and the thickness of HTS tape.

The high-temperature superconducting (HTS) null-flux electrodynamic suspension (EDS) system is one of the most promising solutions for high-speed transportation. In this article, a 3-D model based on the finite-element method (FEM) is established to solve the electromagnetic forces in the HTS null-flux EDS system with the commercial software COMSOL Multiphysics. The current induced in the null-flux coils and the forces on the HTS magnets were studied and compared with the results from our dynamic circuit model. The two models agree with each other with a difference of less than 6%. The FEM model can deal with 3-D geometries, allowing the analysis of complex situations, such as the eddy current in the cryostat walls. Furthermore, the model can be readily extended to solve coupled problems, including the heat and mechanical behaviors of the HTS magnets and/or the null-flux coils, which are engineering concerns in real applications.

With high current-carrying capacity and strong mechanical properties, conductor on round core (CORC) cable is widely adopted in high-field magnet applications, for instance, in the form of solenoids, double pancakes and canted cosine theta coils. However, CORC cable may be twisted in the fabrication of magnet with complex structure, as well as suffering huge Lorentz force in the operation process, which could pose unpredictable strain on helical superconducting tape, arousing secondary damage. In this paper, single layer and double layer CORC samples were fabricated to test their torsion performance through both numerical and experimental methods. Critical twisting angle would be analyzed from the aspect of critical current degradation. Result shows that, compared to additional strain on tape, geometric distortion due to multi-layer structure of CORC cable is more harmful to current-carrying performance of cable. Conclusion obtained from this paper could provide important data for future optimization.