Search Results (26)

Optically pumped magnetometer OPM-MEG has the potential to replace the traditional low-temperature superconducting quantum interference device SQUID-MEG. Coherence analysis can be used to evaluate the functional connectivity and reflect the information transfer process between brain regions. In this paper, a finger tapping movement paradigm based on auditory cues was used to measure the functional signals of the brain using OPM-MEG, and the coherence between the primary motor cortex (M1) and the primary motor area (PM) was calculated and analyzed. The results demonstrated that the coherence of the three frequency bands of Alpha (8–13 Hz), Beta (13–30 Hz), and low Gamma (30–45 Hz) and the selected reference signal showed roughly the same position, the coherence strength and coherence range decreased from Alpha to low Gamma, and the coherence coefficient changed with time. It was inferred that the change in coherence indicated different neural patterns in the contralateral motor cortex, and these neural patterns also changed with time, thus reflecting the changes in the connection between different functional areas in the time-frequency domain. In summary, OPM-MEG has the ability to measure brain coherence during finger movements and can characterize connectivity between brain regions. Full article

The High-Intensity Heavy-Ion Accelerator Facility (HIAF) is a significant national science and technology infrastructure project, constructed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). It is designed to provide intense proton, heavy ion beams, and target-produced radioactive ion beams for nuclear physics and related research. Large-aperture, high-precision, room-temperature, and superconducting dipole magnets are extensively used to achieve high-intensity beams. However, for large-scale magnets (particularly superconducting magnets), the traditional Hall probe mapping measurement platform encounters several limitations: a long preparation time, high cost, low testing efficiency, and positional inaccuracies caused by repeated magnet disassembly. This paper presents a new magnetic field mapping measurement system incorporating ultrasonic motors operable in strong magnetic fields (≥7 T), enabling portable, highly efficient, and high-precision magnetic field measurements. After system integration and commissioning, the prototype dipole magnet for the high-precision spectrometer ring (SRing) was measured. The measurement system demonstrated superior accuracy and efficiency compared with traditional Hall probe mapping systems. On this basis, the magnetic field distribution and integral excitation curve of all 11 warm-iron superconducting dipole magnets and 3 anti-irradiation dipole magnets in the HIAF fragment separator (HFRS) were measured. Each magnet took less than 1 day to measure, and all magnetic field measurement results met the physical specifications. Full article

The integration of more-electric technologies into aero-engines has revolutionized their multi-power architectures, substantially improving system maintainability and operational reliability. This advancement has established more-electric systems as a cornerstone of modern aerospace electrification research. Concurrently, liquid hydrogen (LH₂) emerges as a transformative solution for next-generation power generation systems, particularly in enabling the transition from 100 kW to megawatt-class propulsion systems. Beyond its superior energy density, LH₂ demonstrates dual functionality in thermal management: it serves as both an efficient coolant for power electronics (e.g., controllers) and a cryogenic source for superconducting motor applications. This study systematically investigates the electrification pathway for LH₂-fueled aero-engine multi-electric systems. First, we delineate the technical framework, elucidating its architectural characteristics and associated challenges. Subsequently, we conduct a comprehensive analysis of three critical subsystems including LH₂ storage and delivery systems, cryogenic cooling systems for superconducting motors, and Thermal management systems for high-power electronics. Finally, we synthesize current research progress and propose strategic directions to accelerate the development of LH₂-powered more-electric aero-engines, addressing both technical bottlenecks and future implementation scenarios. Full article

The present work demonstrates a comparative study of hydrogen fuel cells and combustion aircraft to investigate the potential of fuel cells as a visionary propulsion system for radically more sustainable medium- to long-range commercial aircraft. The study, which considered future airframe and propulsion technologies under the Se2A project, was conducted to quantify potential emissions and costs associated with such aircraft and to determine the benefits and drawbacks of each energy system option for different market segments. Future technologies considered in the present work include laminar flow control, active load alleviation, new materials and structures, ultra-high bypass ratio turbofan engines, more efficient thermal management systems, and superconducting electric motors. A multi-fidelity initial sizing framework with coupled constraint and mission analysis blocks was used for parametric airplane sizing and calculations of all necessary characteristics. Analyses performed for three reference aircraft of different sizes and ranges concluded that fuel-cell aircraft could have operating cost increases in the order of 30% compared to hydrogen combustion configurations and were caused by substantial weight and fuel burn increases. In-flight changes in emissions of fuel cell configurations at high altitudes were progressively reduced from medium-range to long-range segments from being similar to hydrogen combustion for medium-range to 24% for large long-range aircraft, although fuel cell aircraft consume 22–30% more fuel than combustion aircraft. Results demonstrate a positive environmental impact of fuel cell propulsion for long-range applications, the possibilities of being a more emission-universal solution, if desired optimistic technology performance metrics are satisfied. The study also demonstrates progressively increasing technology requirements for larger aircraft, making the long-range application’s feasibility more challenging. Therefore, substantial development of fuel cell technologies for long-range aircraft is imperative. The article also emphasizes the importance of airframe and propulsion technologies and the necessity of green hydrogen production to achieve desired emissions. Full article

The intensive development of hydrogen technologies has made very promising applications of one of the cheapest and easily produced bulk MgB₂-based superconductors. These materials are capable of operating effectively at liquid hydrogen temperatures (around 20 K) and are used as elements in various devices, such as magnets, magnetic bearings, fault current limiters, electrical motors, and generators. These applications require mechanically and chemically stable materials with high superconducting characteristics. This review considers the results of superconducting and structural property studies of MgB₂-based bulk materials prepared under different pressure–temperature conditions using different promising methods: hot pressing (30 MPa), spark plasma sintering (16–96 MPa), and high quasi-hydrostatic pressures (2 GPa). Much attention has been paid to the study of the correlation between the manufacturing pressure–temperature conditions and superconducting characteristics. The influence of the amount and distribution of oxygen impurity and an excess of boron on superconducting characteristics is analyzed. The dependence of superconducting characteristics on the various additions and changes in material structure caused by these additions are discussed. It is shown that different production conditions and additions improve the superconducting MgB₂ bulk properties for various ranges of temperature and magnetic fields, and the optimal technology may be selected according to the application requirements. We briefly discuss the possible applications of MgB₂ superconductors in devices, such as fault current limiters and electric machines. Full article

At present, HTS magnets cannot operate in the real closed-loop persistent current mode due to the existence of joint resistance, flux creep, and AC loss of the HTS tape. Instead of using a current source, HTS flux pumps are capable of injecting flux into closed HTS magnets without electrical contact. This paper presents a practical superconducting DC dynamo for charging a conduction-cooled HTS magnet system based on a flux-pumping technique. To minimize heat losses, the rotor is driven by a servo motor mounted outside the vacuum dewar by utilizing magnetic fluid dynamic sealing. Different parameters, such as air gap and rotating speed, have been tested to investigate the best pumping effect, and finally, it successfully powers a 27.3 mH HTS non-insulated double-pancake coil to the current of 54.2 A within 76 min. As a low-cost and compact substitute for the traditional current source, the realization of a contactless DC power supply can significantly improve the flexibility and mobility of the HTS magnet system and could be of great significance for the technological innovation of future HTS magnets used in offshore wind turbines, biomedical, aerospace, etc. Full article

Superconducting electric motors are required in order to deliver lower-carbon aviation. Critical to the success and viability of operating superconducting electric motors in aviation is keeping the superconducting coils at their operating temperature. This paper examines the challenges of keeping a superconducting motor cold if it were used on a single aisle passenger aircraft such as an Airbus A320. The cooling problem is defined and different cooling scenarios are investigated to determine viability. The investigation has shown that for a motor with a superconducting rotor only (copper stator), a Stirling-type cryocooler would be sufficient. However, if the motor is to be fully superconducting, then the cooling loads of the stator, which are much higher, make mechanical refrigeration impractical and the only option is to cool the motor with the heat sink of a liquid hydrogen fuel. Full article

With the continuous advancement of science and technology, the application of high-temperature superconductivity has developed rapidly. The high-temperature superconducting (HTS) motor replacing the copper coil in the traditional motor with HTS winding is increasingly used in power equipment, and the effective thermal management of HTS winding is vital in ensuring the life and effective operation of the HTS motor. In this study, five enhancement structures of indirect oil cooling channels were designed to improve the heat dissipation capacity of the HTS motor winding, and the enhancement effects of the different structures were comprehensively evaluated through numerical simulation using Fluent software 2022R1. The best enhancement structure was selected through structural optimization. The results showed that the Nusselt number of the gap-type enhanced structure was higher than that of the V- and staggered-type structures at the same flow velocity and 68% higher than that of the bare pipe. At the same inlet flow velocity and with a pressure drop limit of 30 kPa, the performance evaluation criterion value of the gap-type structure was 39% and 63% higher than that of the staggered- and V-type structures, respectively. The gap type is the optimal enhancement structure and can effectively improve the heat dissipation of the HTS winding coil. Full article

In line with global environmental regulations, the demand for eco-friendly and highly efficient aircraft propulsion systems is increasing. The combination of axial flux motors and superconductors could be a key technology used to address these needs. In this paper, an axial flux high temperature superconducting (HTS) motor for aircraft propulsion was designed and its characteristics were analyzed. A 2G HTS wire with high magnetic flux characteristic was used for the field winding of the 120 kW axial flux HTS motor, and the rotational speed and rated voltage of the motor were 2000 rpm and 220 V, respectively. The axial flux HTS motor implements a revolving armature type for solid cooling of the HTS field coil. The electromagnetic and thermal features of the motor were analyzed and designed utilizing a 3D finite element method program. The HTS coil was maintained at the target temperature by effectively designing the current lead and cooling system to minimize heat loss. These results can be effectively used in the design of propulsion systems for large commercial aircraft in the future as well as for the design of small aircraft with less than 4 seats. Full article

As a new type of magnetic levitation train with the characteristics of self-stabilization and self-suspension, high-temperature superconducting magnetic levitation has developed to the test line research stage. In order to promote the rapid development of high-temperature superconducting magnetic levitation train engineering, and the main electromagnetic radiation sources are clarified by analyzing their working principles and structures. Then Ansoft Maxwell EM was used to build a 3D magnetic levitation train electromagnetic environment simulation model to simulate and predict the electromagnetic radiation characteristics of the magnetic levitation train system. Finally, a field EMF test was carried out to verify and assess the impact on the EM environment in the system. The results show that the permanent magnet track on the ground and the synchronous linear motor are the primary electromagnetic radiation sources, and the generated fields are mainly low-frequency fields and static magnetic fields. The low-frequency magnetic field inside the train decreases with the increase of frequency and is partially shielded by the carriage; The static magnetic field cannot be weakened by the carriage, and the static magnetic field inside the car decreases with the increase of height. All types of electromagnetic fields are far below the requirements of the relevant electromagnetic environmental standard limits, and have no effect on the electromagnetic radiation safety of the personnel inside the train and the surrounding environment; In considering of the special people who have pacemakers, static magnetic field suppression measures are studied, and the results show that the trains with high magnetic permeability permalloy as the shielding layer at the bottom of the vehicle greatly lower the static magnetic field within the train. Full article

As the demand for eco-friendly energy increases, hydrogen energy and liquid hydrogen storage technologies are being developed as an alternative. Hydrogen has a lower liquefaction point and higher thermal conductivity than nitrogen or neon used in general cryogenic systems. Therefore, the application of hydrogen to cryogenic systems can increase efficiency and stability. This paper describes the design and analysis of a cryogenic cooling system for an electric propulsion system using liquid hydrogen as a refrigerant and energy source. The proposed aviation propulsion system (APS) consists of a hydrogen fuel cell, a battery, a power distribution system, and a motor. For a lab-scale 5 kW superconducting motor using a 2G high-temperature superconducting (HTS) wire, the HTS motor and cooling system were analyzed for electromagnetic and thermal characteristics using a finite element method-based analysis program. The liquid hydrogen-based cooling system consists of a pre-cooling system, a hydrogen liquefaction system, and an HTS coil cooling system. Based on the thermal load analysis results of the HTS coil, the target temperature for hydrogen gas pre-cooling, the number of buffer layers, and the cryo-cooler capacity were selected to minimize the thermal load of the hydrogen liquefaction system. As a result, the hydrogen was stably liquefied, and the temperature of the HTS coil corresponding to the thermal load of the designed lab-scale HTS motor was maintained at 30 K. Full article

Hydrogen as an energy carrier is a promising alternative to fossil fuels, and it becomes more and more popular in developed countries as a carbon-free fuel. The low boiling temperature of hydrogen (20 K or −253.15 °C) provides a unique opportunity to implement superconductors with a critical temperature above 20 K such as MgB₂ or high-temperature superconductors. Superconductors increase efficiency and reduce the loss of energy, which could compensate for the high price of LH₂ to some extent. Norway is one of the pioneer countries with adequate infrastructure for using liquid hydrogen in the industry, especially in marine technology where a superconducting propulsion system can make a remarkable impact on its economy. Using superconductors in the motor of a propulsion system can increase its efficiency from 95% to 98% when the motor operates at full power. The difference in efficiency is even greater when the motor does not work at full power. Here, we survey the applications of liquid hydrogen and superconductors and propose a realistic roadmap for their synergy, specifically for the Norwegian economy in the marine industry. Full article

MgB₂ pellets that were sintered by Spark Plasma Sintering (SPS) from commercial MgB₂ powder were soldered by a SPS process and compared to unsoldered ones. The soldered samples were characterized by scanning and transmission electron microscopy which have shown no visible defects at the junction. SQUID magnetometry and four probes resistance measurements have confirmed that the soldered pellets present the same magnetic properties as the unsoldered ones. The presented soldering technique could find applications for manufacturing superconducting devices with custom shapes which could be used as rotors for motors and generators, magnets and magnetic shields. This new approach could generate a high potential interest for industrials in these and connected domains such as the development of new electrical planes using superconducting technologies. Full article

In this paper, a new superconducting flywheel energy storage system is proposed, whose concept is different from other systems. The superconducting flywheel energy storage system is composed of a radial-type superconducting magnetic bearing (SMB), an induction motor, and some positioning actuators. The SMB is composed of a superconducting stator and a flywheel rotor. The flywheel rotor is suspended by the superconducting stator, whose one end is fixed to a stable and heavy base. Free-run experiments in the case of the unfixed stator are performed. The natural rotation decay curve, displacement at the upper position of the rotor and displacement at a lower position of the rotor are measured. Moreover, free-run experiments in the case of the fixed stator are performed, and the same dynamic characteristics of the unfixed stator are measured. Especially, impulse responses for the rotor in the case of an unfixed stator are very different from those in the case of a fixed stator. The experimental results discuss some important characteristics of the superconducting flywheel energy storage system, whose rotor is suspended by the superconducting stator. Full article

Developing a joining technology for 2G HTS tapes without significantly reducing their superconducting property is crucial for numerous applications (MRI, motor/generator, power transmission, etc.). In this study, low sintering temperature (~230 °C) nano-silver paste was used as solder to join two 2G HTS tapes. In addition, two heating methods, i.e., furnace heating (heat flux outside-in) and resistive Joule heating (heat flux inside-out), were studied. This study indicates that the heat flux from internal by resistive Joule heating method shows less deteriorating impact to the 2G RE-Ba-Cu-O tape (RE: rare earth element) during the sintering process with the best specific resistance of 0.074 μΩ∙cm² and I_c retention percentage of 99% (i.e., I_c reduced from 100 A before joining to 99 A after joining). This study indicates that nano-silver paste together with resistive Joule heating can possibly be used as soldering materials to join 2G HTS tapes. Full article