High-temperature Superconducting Materials Research Articles

Fabrication of a 25.2 T NMR magnet for an extreme condition user facility in China

Abstract An ultra-high field magnet (> 20 T) is desirable to study material characteristics under extreme magnetic condition with the use of magnetic resonance for a higher signal-to-noise ratio, better sensitivity and a higher spectral resolution. The fabrication of an ultra-high field magnet requires high-temperature superconducting materials like REBSO and BSCCO, which have higher critical temperature and current density as compared to conventional low-temperature superconducting materials. Despite the benefits of BSCCO for better field homogeneity and stability due to its smaller screening currents, it is technically challenging to use it in magnet fabrication due to the greater variations in tape thickness and width. In this highlighted study, an optimization procedure was developed to randomly re-order the wound double-pancake coils as well as optimize the winding turns based on pre-winding measurements. Such optimizations enable the fabrication of a magnet with high homogeneity that is suitable for use in nuclear magnetic resonance.

Gamma radiation effects on high-temperature superconducting ReBCO tape

High-temperature superconducting (HTS) magnets are crucial components in future fusion reactors, subjected to prolonged irradiation and complex mechanical conditions. While the irradiation sensitivity of HTS materials has been extensively studied, limited research has explored the effects of force conditions during irradiation. This study investigated the influence of irradiation on ReBCO tapes. An irradiation experiment was conducted utilizing a Co60 source irradiation device. Superconductor properties were evaluated through the induction method, while microstructure analysis was performed using x-ray diffraction measurements. The results indicate that the critical current initially increases and subsequently decreases, while the critical temperature remains relatively stable. Furthermore, the bending degree during irradiation affects the critical current density, with a decrease in radius corresponding to a first increase and then subsequent decrease in critical current density. The force applied during irradiation exhibits a impact on the superconducting properties, underscoring the importance of considering force conditions in future investigations.

Experimental study on the an-isotropic critical current of REBCO tape.

Superconducting magnets are widely used in nuclear fusion reactors, high-energy particle accelerators, steady-state high magnetic fields, etc. Higher magnetic fields and higher operating temperatures are two application trends. High temperature superconducting (HTS) materials are the only choice for high temperature and high field magnets in the future. The first- and second-generation HTS materials have a typical tape structure; their critical performance is magnetic field angle and temperature dependent. A new test facility is developed for an experimental study on the an-isotropic critical current. The field angle can be changed from 0° to 360° with a resolution of 1°. The rotation deviation angle is measured to be 0.2° when the upper part rotates 90°. The temperature can be changed from 4.2 to 80K. The temperature errors are ±50, ±80, and ±135 mK for 4.2-20, 20-40, and 40-80K, respectively. The angle dependence of critical current (Ic) of the tested rare-earth barium copper oxide tape within 0°-30° is strong. From 30° to 90°, the sample Ic almost does not change with the magnetic field angle. The implementation of the project will not only promote the structural optimization of HTS tapes but also promote the miniaturization and economical application of HTS magnets.

Radiation protection methods for suborbital aircrafts

This paper presents the outcomes of a study conducted by SALTO team in the framework of the Student Aerospace Challenge, focusing on designing structures to optimize passenger protection against radiation in a suborbital vehicle. The study delves into space radiation characteristics and their potential impact on human health during suborbital flights. Through comprehensive research and the utilization of CARI-7A software, the team evaluated radiation exposure and explored both passive and active shielding solutions. The passive shielding solution involved the design of a multifunctional sandwich panel and a shielding layout for windows, minimizing weight penalties on the vehicle’s structure. Additionally, an active shielding concept utilizing high-temperature superconductor material and solenoid layouts was investigated. The study underscores the benefits and challenges associated with both passive and active shielding methods, emphasizing the importance of further exploration to enhance suborbital flight safety and pave the way for future human space exploration endeavors.

Prediction of ambient pressure superconductivity in cubic ternary hydrides with MH6 octahedra

Exploring high-temperature superconducting (high-Tc) material at ambient pressure holds immense significance for physics, chemistry, and materials science. In this study, we perform a high-throughput screening of strong electron-phonon interactions in X2MH6 compounds (X = Li, Na, Mg, Al, K, Ca, Ga, Rb, Sr, and In; M are 3d, 4d, and 5d transition metals). These compounds have a cubic structure featuring an MH6 octahedron motif. Our screening calculations suggest that 26 compounds exhibit dynamic stability and strong electron-phonon coupling. Among them, Mg2RhH6, Mg2IrH6, Al2MnH6, and Li2CuH6 show promising energetic stability and Tc of more than 50 K at ambient pressure. This study underscores promising high-Tc compounds at ambient pressure with distinctive MH6 motifs.

Cryogen-free 400-MHz nuclear magnetic resonance spectrometer as a versatile tool for pharmaceutical process analytical technology.

The discovery of new ceramic materials containing Ba-La-Cu oxides in 1986 that exhibited superconducting properties at high temperatures in the range of 35 K or higher, recognized with the Nobel Prize in Physics in 1987, opened a new world of opportunities for nuclear magnetic resonance (NMRs) and magnetic resonance imaging (MRIs) to move away from liquid cryogens. This discovery expands the application of high temperature superconducting (HTS) materials to fields beyond the chemical and medical industries, including electrical power grids, energy, and aerospace. The prototype 400-MHz cryofree HTS NMR spectrometer installed at Amgen's chemistry laboratory has been vital for a variety of applications such as structure analysis, reaction monitoring, and CASE-3D studies with RDCs. The spectrometer has been integrated with Amgen's chemistry and analytical workflows, providing pipeline project support in tandem with other Kinetic Analysis Platform technologies. The 400-MHz cryofree HTS NMR spectrometer, as the name implies, does not require liquid cryogens refills and has smaller footprint that facilitates installation into a chemistry laboratory fume hood, sharing the hood with a process chemistry reactor. Our evaluation of its performance for structural analysis with CASE-3D protocol and for reaction monitoring of Amgen's pipeline chemistry was successful. We envision that the HTS magnets would become part of the standard NMR and MRI spectrometers in the future. We believe that while the technology is being developed, there is room for all magnet options, including HTS, low temperature superconducting (LTS) magnets, and low field benchtop NMRs with permanent magnets, where utilization will be dependent on application type and costs.

Effect of doping on evolution of He<sup>+ </sup>ion irradiation defects and superconductivity in EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7–δ</sub> superconducting strips

Rare-earth barium copper oxide (REBCO) as a representative of the second-generation high-temperature superconducting materials possesses superior physical advantages such as high critical magnetic field, elevated critical temperature, and superior current density, which has been applied to many domains. Although the introduction of non-superconducting nanoscale particle dopants, as a critical method, can enhance the magnetic flux pinning capability of REBCO strips, the effect of the doping on the performance change and microstructure evolution of the strips under irradiation is ignored. In this work, undoped and 3.5 mol% BaHfO<sub>3</sub> (BHO) doped EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7–δ</sub> strips are investigated in the room-temperature irradiation experiments (1.4 MeV He<sup>+</sup> ions) with three distinct doses of 5×10<sup>14</sup>, 5×10<sup>15</sup>, and 5×10<sup>16</sup> ions/cm<sup>2</sup>, respectively. Electrical performance tests reveal that the undoped strips exhibit a slight increase in <i>J</i><sub>c</sub> after the low-dose irradiation. However, with dose increasing, <i>J</i><sub>c</sub> decreases by over 60%. In contrast, doped strips experience a significantly smaller decline in <i>J</i><sub>c</sub>, ranging only between 30% and 40% at high-dose irradiation. Raman spectroscopy and transmission electron microscopy characterizations confirm that the defects induced by He<sup>+</sup> ion irradiation lead to amorphization and structural disorder within the superconducting layers, which is the primary reason for the decline in the superconducting properties of the strips. The results show that the introduction of localized strain through BHO nanophase in the superconducting layer changes the migration and aggregation behavior of irradiation-induced defects, repairing the damaged superconductor structure. Furthermore, the field dependence and temperature dependence of <i>J</i><sub>c</sub> of doped strips are irradiation-resistant due to BHO nanocrystals as strong pinning centers. Additionally, unlike the superconducting properties of the REBCO strips that can be repaired through oxygen annealing after neutron or heavy ion irradiation, the electrical properties of the two types of strips irradiated with high doses of He<sup>+</sup> ions in this work are further deteriorated after being annealed. It is worth noting that compared with the undoped strip, the localized strain generated by BHO in the doped strip inhibits the size growth of helium defects in the three-dimensional direction at high temperatures, which changes the magnetic flux pinning characteristics and delays the disorder and amorphization of the superconducting layer structure caused by the severe growth of helium bubbles. This study provides a reference for the application of REBCO superconducting strips in the irradiation environment.

Enhancing Adrenaline Sensing with Lanthanum Cuprate: A Promising Approach for a Novel Sensor

Electrochemical sensing is an excellent analytical means with multiple applications. Most of the electrochemical developments are based on the novel electrochemically active substrates. A lot of them have been adopted from other fields of material science. Every new class of functional materials has impacted on the development of electroanalytical chemistry. In this view, lanthanide cuprates, a well recognized high temperature superconducting materials were considered for adrenaline sensing. Obtained from corresponding oxides, a highly crystalline La2CuO4 found to be a suitable substrate for analytical method development. It inherited sponge-like morphology common for the most of the previously reported lanthanum cuprates with narrow pore size distribution at 400–700 nm. Excellent charge mobility and low resistivity provided a carbon paste electrode with improved linearity range and low limit of detection. Repeatability and stability of the developed sensor were at satisfactory level. Sensor functionality was verified on the real samples with excellent recovery rates. With this work we suggest further development of electroanalytical methods with application of lanthanide cuprates.

A systematic study on the phase diagram and superconductivity of ternary clathrate Ca-Sc-H at high pressures.

This work explores potential high-temperature superconductor materials in hydrogen-rich systems. Here, the crystal structure stabilities of ternary Ca-Sc-H systems under high-pressure (P = 100-250 GPa) and their superconductivities are investigated using the particle swarm optimization methodology combined with first-principles calculations. For the predicted candidate structures of Ca-Sc-H systems, the pressure-dependent phase diagram and thermodynamic convex hull were investigated across a wide range of compositions; the electronic properties of all the predicted phases were analyzed in detail to study the bonding behavior of these stable phases. We identified the crystal structures of four thermodynamically stable compounds: R3̄m-CaScH6, Immm-CaSc2H9,C2/m-Ca2ScH10, and R3̄m-CaScH12. Among them, R3̄m-CaScH12 was predicted to have the highest Tc value (i.e., 173 K) at 200 GPa. The discovery of this previously unreported pressure-induced decomposition of Ca-Sc-H systems will pave the way for investigations on the nature of hydrogen-metal interactions.

Overall design of a 5 MW/10 MJ hybrid high-temperature superconducting energy storage magnets cooled by liquid hydrogen

The integration of superconducting magnetic energy storage (SMES) into the power grid can achieve the goal of storing energy, improving energy quality, improving energy utilization, and enhancing system stability. The early SMES used low-temperature superconducting magnets cooled by liquid helium immersion, and the complex low-temperature cooling system greatly limited the promotion and application of such devices. SMES based on high temperature superconductivity (HTS) materials can operate in the temperature range of 15–30 K, which simplifies the cooling system and reduces the cooling loss, and greatly improves the operating efficiency and stability of the cooling system. In this paper, the overall design of a 5 MW/10 MJ SMES based on state of the art HTS materials is achieved. The structural parameters of YBCO and MgB2 cables are introduced and the structural parameters of energy storage magnet are analyzed. And the cooling scheme for SMES is provided.

Fault current limiter based on high temperature superconductors

High Temperature Superconductors (HTS) made the Superconducting Fault Current Limiter (SFCL) a reality in power electric grids. Resistive SFCL, which is the subject of this article, is based on a unique property of superconductors to quench from a non-dissipative to a high dissipative state above a given current. SFCL is an attractive response to the poorly solved problem of fault currents in power electric grids and makes it possible to enhance the security and quality of electricity, something that matters more than ever. Liquid nitrogen cryogenics – which is possible thanks to HTS- makes the cryogenics user friendly. In-field SFCL operations confirm this. Second generation (2 G) HTS materials or Coated Conductors suit well to SFCL. Due to its high interest, SFCL has been the subject of a great deal of research and development. In terms of Technology Readiness Level (TRL) it reaches 8 with several in grid test experiences.Here a short history of SFCL is presented with a highlight about Curl 10, Ampacity and SuperOx devices. The two major locations in the grid are reported: grid coupling and feeder protection. The quench phenomena is described in a bit more detail before the basic design (length and cross section) is presented. The design is primarily thermal, considering two extreme operations: fault with very high prospective current (clear short-circuit) and fault with prospective current close to the minimum runaway current along the length. This operation is called the hot spot one. It is due to the intrinsic variation of the critical current along the length and to the low Normal Zone Propagation Velocity (NZPV). The cost of the superconducting conductor is given, showing no bottleneck for an economic development. All the more it is still possible to lower the cost with some developments. This article ends with two real advances presently underway: Current Flow Diverter (CFD) and Sapphire substrate superconducting 2 G tape. CFD aims to increase the NZPV, to still further secure the operation and to reduce the conductor cross section. The use of sapphire substrates allows to reduce significantly the length of the design.

Unraveling quench dynamics and real-time continuous detection in HTS tapes through distributed fiber optic sensing

High-temperature superconducting (HTS) tapes, coils, and magnets often experiences intricate quench instabilities and failures during high current-carrying operations, posing challenges to their practical applications. This study addresses the need for a measurement approach capable of monitoring multi-field signals in superconducting structures within cryogenic and extreme electromagnetic environments. We explore the application of distributed fiber optic sensing (DFOS) technology, specifically employing the optical frequency domain reflectometry scheme, which offers distinct advantages over traditional point-type electrical testing methods, particularly for superconducting materials and magnets. In this experimental study, we continuously track the quench evolution process in superconducting tapes using both bonded and stress-free fibers for real-time monitoring. A comprehensive analysis of the acquired temperature and thermoelastic strain profiles provides essential insights into the dynamic behavior of quench events. The findings demonstrate the effectiveness of DFOS in identifying and characterizing the onset and propagation of quenches. By arranging bonded and stress-free fibers in parallel on the HTS tape’s surface, we successfully decouple the effects of strain-temperature cross-sensitivity, enabling the extraction of temperature and train profiles. The bonded fiber optic sensor demonstrates rapid sensitivity to the thermally quenched events. Temporal derivatives of voltage and thermal strain exhibit characteristic plateaus and slope changes during quenches, respectively. The voltage rate displays two plateaus corresponding to superconducting-to-normal transitions, while strain rates exhibit potential as criteria for identifying quench events in HTS materials. Moreover, DFOS outperforms traditional terminal average voltage measurement, capturing quench evolution tails from the initial point of quench until the complete transition of the segment into the normal state. This experiment provides a solid foundation for further exploration of the underlying quench mechanism.

Engineering REBCO high temperature superconductor materials for applications

This article is a lookback at the road traveled in the last 36 years to realize the abundant potential of high temperature superconductors (HTS) that had evoked worldwide excitement on their discovery. Numerous advances have been made in the materials science and manufacturing of HTS to overcome the many obstacles in implementing them in applications.

The research on the influence mechanism of internal deformation for the performance of Bi-2212

Cable-in-conduit conductor (CICC), one of the most promising conductors for manufacturing magnets in magnetic confinement fusion devices, has attracted lots of attention. In the production of CICC, porosity control is necessary for its stability. The porosity control is usually realized by the diameter-reducing process, which would also lead to indentation damages to the elements of CICC-superconducting wires. In this article, systematic research of indentation damages was carried out on the next generation of high-temperature superconducting materials–Bi-2212 wires. The results indicate that the current carrying capacity of the indentation-damaged wire would first keep steady and then show exponential decline with the increase of indentation depth. The wires subjected to pre-overpressure (pre-OP) treatment exhibit slightly improved resistance against indentation damage at shallow indentation depths. However, their critical current (I c) deteriorates more rapidly at greater indentation depths when compared to wires that have not undergone the per-OP process. The following structural characterization analyzed the reasons for the property changes with the help of scanning electron microscopy, energy dispersive x-ray spectroscopy, computed tomography, and hardness tester. Misalignment between the Bi-2212 grains and shaped filaments was found in the indentation-damaged wires, with which the degradation in I c of the wires and the differences in properties of the two kinds of wires were further discussed.

A Measuring System for HTS Wires and Coils Properties at Low Temperatures

The use of high temperature superconducting materials (HTS) in various applications, requires knowledge of their critical parameters like critical current, critical magnetic field and critical temperature, in DC applications like high magnetic field generators, superconducting magnetic energy storage system (SMES), magnetic resonance imaging (MRI), magnets for particle accelerators, SC Maglev trains and other applications. Also, these parameters are important for specific properties in alternating current applications like fault current limiters, transformers, generators, motors, and power transmission lines. An important characteristic that needs to be tucked into consideration for AC applications is the power losses that occur in the HTS superconducting materials, which limits the maximum performance that the superconducting materials can attain for these applications. In order to measure these characteristics, which depend on the type of material used, but also on the temperature and other parameters, it is necessary to use an appropriate setup device that allows both obtaining the working temperature range (4.2 K to 300 K and other necessary parameters like high vacuum 10-6 mbar, high current supply (500 A), high magnetic field measurement system (1-10 T), etc. For the cryogenic cooling of the entire system, a closed cycle Gifford-McMahon type cryocooler is used, with two cooling stages, stage I at 50 K and second stage at 4.2 K (liquid Helium temperature). The set-up system used for measurement of the parameters of HTS superconducting materials (YBCO, BSCCO or MgB2) and the various coils made with them, is described in this article together with its functional parameters and some experimental results obtained by testing an YBCO coils system. The maximum generated magnetic flux density was 5 T in the centre of the coils system.

Anisotropic NMR data acquisition with a prototype 400 MHz cryogen-free NMR spectrometer.

High-temperature superconducting (HTS) materials have recently been incorporated into the construction of HTS cryogen-free magnets for nuclear magnetic resonance (NMR) spectroscopy. These HTS NMR spectrometers do not require liquid cryogens, thereby providing significant cost savings and facilitating easy integration into chemistry laboratories. However, the optimal performance of these HTS magnets against standard cryogen NMR magnets must be evaluated, especially with demanding modern NMR applications such as NMR in anisotropic media. The stability of the HTS magnets over time and their performance with complex pulse sequence experiments are the main unknown factors of this new technology. In this study, we evaluate the utility of our prototype 400 MHz cryogen-free power-driven HTS NMR spectrometer, installed in the fumehood of a chemistry laboratory, for stereochemical analysis of three commercial natural products (artemisinin, artemether, and dihydroartemisinin) via measurement of anisotropic NMR data, in particular, residual dipolar couplings. The accuracy of measurement of the anisotropic NMR data with the HTS magnet spectrometer is evaluated through the CASE-3D fitting protocol, as implemented in the Mestrenova-StereoFitter software program.

Conceptual Design of 20 T Hybrid Accelerator Dipole Magnets

Hybrid magnets are currently under consideration as an economically viable option towards 20 T dipole magnets for next generation of particle accelerators. In these magnets, High Temperature Superconducting (HTS) materials are used in the high field part of the coil with so-called insert coils, and Low Temperature Superconductors (LTS) like Nb3Sn and Nb-Ti superconductors are used in the lower field region with so-called outsert coils. The attractiveness of the hybrid option lays on the fact that, on the one hand, the 20 T field level is beyond the Nb3Sn practical limits of 15-16 T for accelerator magnets and can be achieved only via HTS materials; on the other hand, the high cost of HTS superconductors compared to LTS superconductors makes it advantageous exploring a hybrid approach, where the HTS portion of the coil is minimized. We present in this paper an overview of different design options aimed at generating 20 T field in a 50 mm clear aperture. The coil layouts investigated include the Cos-theta design (CT), with its variations to reduce the conductor peak stress, namely the Canted Cos-theta design (CCT) and the Stress Management Cos-theta design (SMCT), and, in addition, the Block-type design (BL) including a form of stress management and the Common-Coil design (CC). Results from a magnetic and mechanical analysis are discussed, with particular focus on the comparison between the different options regarding quantity of superconducting material, field quality, conductor peak stress, and quench protection.

Modelling of a High-Temperature Superconductor HVDC Cable Under Transient Conditions

The carbon neutrality goal of achieving net-zero by 2050 has sparked significant interest in offshore wind farms. With the offshore wind farms installed > 100 km away from the seashore, underground power transmission infrastructure is a necessity. Considering the power cable length and low net effective losses, a high-voltage direct-current (HVDC) system is chosen for this study. Also being lossless in DC operation, the HVDC cables are considered to be made out of high-temperature superconductor (HTS) material. But, unlike copper/aluminium, HTS material has a sharp transient behaviour as a function of the operating current, temperature and field. Thus, under transient conditions, as the fault current ramps up, this can lead to an increase in the HTS operating temperature, causing either degradation or permanent damage to the HVDC cable. In this paper, an HTS HVDC cable model has been developed in MATLAB/Simscape coupling both electrical and thermal models. For this study, a 100 km long coaxial 100 kV/1 GW DC HTS power cable is considered and modelled both as a lumped element and distributed element model with 100 elements to compare and evaluate the cable parameters along the length. The parameters include temperature distribution, resistance, critical current, and losses at different spots throughout the length of the cable. To simulate the transient condition, a line-to-ground (LG) fault is considered and the current distribution between the copper former and HTS tapes is studied. Using this cable model, the maximum temperature of the HTS and coolant both in the superconducting state and transient state are evaluated and presented. In comparison to the distributed model, the lumped model displayed different thermal and electrical values.

A Double Rotor Flux Switching Machine With HTS Field Coils for All Electric Aircraft Applications

The increasing demand for high-power density motors in electric transport industries opens a new research opportunity to develop motor topologies with less weight and high efficiency. In particular, all-electric aircraft applications require very high power density motors. This paper shows the design of a new 1 MW 20-pole/15-slot double rotor flux switching machine with high-temperature superconducting field coils and thermal management system. The proposed motor features an air-core stator. Aluminum Litz wire is used for the armature conductors, and the YBCO- high-temperature superconducting material is used for the field coils. The armature winding and field coils operate at 95K and 65K, respectively. The active part power density including rotors, armature windings and field coils obtained with the proposed design is 29.3kW/kg. The specific power density of proposed motor considering mechanical, support structure and TMS is about 18.5 kW/kg. The efficiency can be higher than 98.7% which satisfies the requirement of electric aviation.

Modeling Eddy Current Losses in HTS Tapes Using Multiharmonic Method

Due to the highly nonlinear electrical resistivity of high temperature superconducting (HTS) materials, computing the steady-state eddy current losses in HTS tapes, under time-periodic alternating current excitation, can be time consuming when using a time-transient method (TTM). The computation can require several periods to be solved with a small time-step. One alternative to the TTM is the multiharmonic method (MHM) where the Fourier basis is used to approximate the Maxwell fields in time. The method allows obtaining the steady-state solution to the problem with one resolution of the nonlinear problem. In this work, using the finite element method with the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H-\varphi$</tex-math></inline-formula> formulation, the capabilities of the MHM in the computational eddy current loss modeling of HTS tapes are scrutinized and compared against the TTM.