Search

Trimethylamine-N-oxide (TMAO), an intestinal flora metabolite of choline, may aggravate atherosclerosis by inducing a chronic inflammatory response and thereby promoting the occurrence of cerebrovascular diseases. Knowledge about the influence of TMAO-related inflammatory response on the pathological process of acute stroke is limited. This study was designed to explore the effects of TMAO on neuroinflammation, brain injury severity, and long-term neurologic function in mice with acute intracerebral hemorrhage (ICH). We fed mice with either a regular chow diet or a chow diet supplemented with 1.2% choline pre- and post-ICH. In this study, we measured serum levels of TMAO with ultrahigh-performance liquid chromatography-tandem mass spectrometry at 24 h and 72 h post-ICH. The expression level of P38-mitogen-protein kinase (P38-MAPK), myeloid differentiation factor 88 (MyD88), high-mobility group box1 protein (HMGB1), and interleukin-1β (IL-1β) around hematoma was examined by western blotting at 24 h. Microglial and astrocyte activation and neutrophil infiltration were examined at 72 h. The lesion was examined on days 3 and 28. Neurologic deficits were examined for 28 days. A long-term choline diet significantly increased serum levels of TMAO compared with a regular diet at 24 h and 72 h after sham operation or ICH. Choline diet-induced high serum levels of TMAO did not enhance the expression of P38-MAPK, MyD88, HMGB1, or IL-1β at 24 h. However, it did increase the number of activated microglia and astrocytes around the hematoma at 72 h. Contrary to our expectations, it did not aggravate acute or long-term histologic damage or neurologic deficits after ICH. In summary, choline diet-induced high serum levels of TMAO increased the cellular inflammatory response probably by activating microglia and astrocytes. However, it did not aggravate brain injury or worsen long-term neurologic deficits. Although TMAO might be a potential risk factor for cerebrovascular diseases, this exploratory study did not support that TMAO is a promising target for ICH therapy.

The higher magnetic field is an everlasting goal for researchers in the field of high-field superconducting magnets, for its vital significance to modern science and technology. After achieving our goal of 25 T superconducting magnet project, we set a more ambitious goal to obtain a central field of 27 T, by upgrading the previous 10 T REBCO (REBa2Cu3Ox, RE = rare earth) insert to 12 T. On the basis of the previous 10 T REBCO insert, the newly designed 12 T REBCO insert has an outer REBCO coil, which has the inner and outer diameters of 125 and 150 mm, respectively, and a height of 85 mm. The current grading method and the detailed stress analysis were employed in the design of the added REBCO coil. Stress analysis showed that the maximum hoop stress was reduced from 470 to 438 MPa after employing winding tension, overbanding, and cooldown. The designed highest engineering current density in this added REBCO coil is 383 A/mm2, much higher compared with the previous REBCO insert, the highest of which is only around 300 A/mm2. The rough operation margin for the previous REBCO coil and the added REBCO coil is 42.6% and 43.7%, respectively. This article mainly introduces the design, fabrication, and test results of the 27 T all-superconducting magnet in detail.

In 2021, the Institute of Electrical Engineering, Chinese Academy of Sciences successfully reached 9.4 T in a whole-body magnetic resonance imaging (MRI) superconducting magnet with an inner diameter of 800 mm. In this study, a systematic analysis of both the real quench protection performance and a simulation are reported. The four successful quench protections during the entire energization process proved the feasibility of the ‘in-out-in’ quench protection protocol for a 9.4 T-800 mm superconducting magnet. The quench trigger sequence was shown to be adjusted by changing the heater thickness, which demonstrates the flexibility of the ‘in-out-in’ quench protection protocol to fit a different MRI magnet design. The high accuracy of the quench protection simulation method and code was confirmed through comparison of the simulation results with the real performance. Moreover, the limitations of the current quench protection and reference value to other MRI magnets were discussed. It is believed that this study will be useful to other research groups and promote the development of an extremely high-field whole-body MRI system.

High field superconducting magnets, as important experimental facilities in condensed matter physics, provide high magnetic field for mapping the Fermi surface of metals, which is a basic approach to study many material properties like resistance, Hall resistance, and magnetic susceptibility. Up to now, the highest magnetic field ever achieved with superconducting magnets is 32 T, obtained at national high magnetic field laboratory (NHMFL) on Dec. 8, 2017, with a 17-T REBCO insert in a 15-T LTS background magnet. Institute of Electrical Engineering (IEE, CAS), has developed high field superconducting magnet for many years, and we successfully tested a 27.2-T superconducting magnet at IEE on Nov. 28, 2017. In the next step, we want to utilize our magnet techniques to fabricate a 30-T superconducting magnet for quantum oscillation application. The magnet will consist of a 15-T/160-mm LTS magnet and a 15-T/35-mm REBCO insert. Electromagnetic design to obtain a higher operation margin and detailed stress analysis will be introduced. Other design considerations will also be given in details and engineering issues will also be discussed.

The intra-layer no-insulation (LNI) coil, which has the advantages of self-protection and high magnetic field homogeneity, is of great potential in HTS NMR and MRI applications. Compared to the more commonly-used double-pancake coils, the transient characteristics are more complex due to additional axial current. While the present circuit model cannot accurately describe the geometry of the LNI coil and the internal characteristics of each turn of the coil, a helical grid equivalent circuit model with consideration of types of mutual inductances is proposed in this paper. In the circuit model, details of the coil are characterized with subdivided helical surface elements in each turn, and each helical surface element can be equivalent to corresponding circuit parameters. The circuit model is verified by a comparison experiment with an intra-layer insulation coil. And elaborate current distributions in each turn of the LNI coil can be obtained with this circuit model. Analysis results demonstrate that the azimuthal current and the axial current are always symmetrically distributed about the middle plane, and the radial current is always anti-symmetrically distributed about the midplane. The circuit model can be used to simulate the quench electromagnetic characteristics of the LNI coil in the future.

Institute of Electrical Engineering, Chinese Academy of Sciences has been focusing on high-field all-superconducting magnet project for many years. No-insulation (NI) winding technology, despite of its charging delay time, makes the magnet of much higher current density, and more important, self-protected. Based on the NI dry-winding technology, a 25 T/32 mm bore superconducting magnet was designed as a combination of 15 T/160 mm bore low temperature superconductor magnet and a 10 T/32 mm bore high temperature superconductor insert. A prototype coil, composed of 15 double pancakes (DPs), was tested at 4.2 K. Test results show that the REBCO insert can generate a 9 T central field in a 15 T background field, and 11.2 T, self-field. While fully evaluation of this insert shows that bad splice joints and premature quenches occurred during the test. We have repaired the bad splice joint, replaced some broken DPs, and rebuilt some double-wound DPs to lower the current density at the top/bottom of the insert to improve the operation margin. After that, we will retest the magnet system. The latest design, construction, and test results of the 25 T all-superconducting magnet will be fully introduced in this paper.

The 9.4-T whole-body MRI superconducting magnet system is under manufacturing in the Institute of Electrical Engineering, Chinese Academy of Sciences (IEE CAS), which is used for the high-resolution imaging on human brain and metabolism. The superconducting magnet system with a warm bore of 800 mm is designed, which has the field homogeneity in a DSV of 400 mm better than 5 ppm after superconducting shimmed. In this paper, the magnet structure and superconducting coils manufacture process are introduced. The progress of wet winding and assembling of the magnet is presented. The optimized superconducting jointing technology is reported. During the coils manufacturing procedure, both the electrical insulation performance and the dimensional precision of the coils are controlled.

The effect of a high magnetic field on the microstructure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy was investigated experimentally. The obtained results indicated that the application of the magnetic field caused the degeneration of the regular lamellar eutectic structure and induced the columnar-to-equiaxed transition (CET) of eutectic dendrites. In addition, the magnetic field modified the macroscopic solid-liquid interface shape and decreased the volume fraction of the Heusler phase. Furthermore, the amplitude and distribution of the thermoelectric magnetic force (TEMF) and thermoelectric magnetic convection (TEMC) in NiAl-Cr(Mo) eutectic alloy during directional solidification under a high magnetic field were studied by numerical simulation at different scales. It was found that the abovementioned results should be attributed to the coupling effects between the TEMC and TEMF. Besides, present work may provide a new method for modification of eutectic morphology during directional solidification under a high magnetic field.

An extreme low-resistance NbTi superconducting wire jointing technology is a key issue for the construction of the scientific superconducting magnet that required high field stability. In this paper, a novel electromagnetic forming NbTi superconducting joint technology was developed. The preliminary experiment was done, and the fabrication technique was researched by changing the parameters. The joint resistances were tested using the coil current decay method. The contact resistance properties of the superconducting joint were investigated. The induced magnetic field and electromagnetic force, plastic deformation, and the electrical contact characteristics of the NbTi superconducting joint were discussed. The preliminary results show that the electromagnetic formed NbTi superconducting joint has excellent electrical interconnection property and easy operation.

Textured porous Si3N4 ceramics with fine and coarse β-Si3N4 powders as the raw materials were prepared by gel casting in a strong magnetic field of 6T and subsequent pressureless sintering. These results showed that highly textured porous Si3N4 ceramics could be obtained by adjusting the ratio between fine and coarse β-Si3N4 powders in 6T. The Lotgering orientation factor in green bodies showed the value of 0.72∼0.74 with the increase of coarse powder content. The sintering process promoted texture development of the samples by Ostwald ripening owing to the big difference in the β-Si3N4 initial powder size. After sintering at 1800oC for 2 h, the degree of texture (Lotgering orientation factor) in the sample, prepared with fine and coarse powders at the ratio of 1:1, reached the maximum value (0.91), and it had relatively high density (66.91%) and low apparent porosity (34.51%). The crystallographic texture in porous Si3N4 ceramics led to the anisotropic bending strength. The method combined with g...

The 25 T/32 mm bore superconducting NMR magnet at Institute of Electrical Engineering, Chinese Academy of Sciences (IEE, CAS) was designed as a combination of 15 T/160 mm bore Low Temperature Superconductor (LTS) magnet and a 10 T/32 mm bore High Temperature Superconductor (HTS) insert, especially wound with ReBCO coated conductors. To overcome the delamination problem of the ReBCO coated conductor in the wet-wound magnet, the conductor for winding the Double Pancakes (DPs) were wrapped with Kapton film to insulate the conductor and the epoxy resin. However, performance test at 77 K shows that Kapton film insulation doesn’t work well all the time, many of the DPs has obvious performance degradation after cool down and warm up, which shows disadvantage of this insulation approach. We then shift our effort from fabricating wet-wound magnet to fabricating Non-Insulated (NI) dry-wound magnet. The ReBCO insert with NI technology, designed with 16 dry-wound DPs, has the inner diameter, outer diameter, and height of 32 mm, 106 mm, and 160 mm, respectively. A DP showing low performance at 77 K was got rid of the assembly and the finally assembled ReBCO insert has the inner diameter of 32 mm, outer diameter of 104 mm and height of 150 mm. Preliminary test shows that the ReBCO can generate a maximum central field of 9 T, 4.2 K in the 15 T background field. We still found bad DP-DP splice joints and premature quenches during the test. Next step on the project is to repair the insert and lower the current density at the top/bottom of the insert to improve the operation margin. Design, fabrication and test of the ReBCO insert are mainly presented in this paper.

The magnetic field inhomogeneity and the Lorentz force of the superconducting magnet for a magnetic resonance image magnet are reduced by optimization of the shape of the ferromagnetic poles. The two objectives are calculated by a commercial software Opera3D-TOSCA based on the finite element method (FEM). A genetic algorithm (GA) improved by adding niching and adaptive algorithms is developed on the computation platform MATLAB. The FEM and the GA is combined for the optimization of the problem. Parallel computation on MATLAB is employed to reduce the time consumption of the optimization. Twice calculations with progressive discretization are performed and satisfactory results with low magnetic field inhomogeneity and very small Lorentz force are obtained.

There are some requirements for the superconducting magnet used as the standard source of magnetic field to calibrate some magnetic probes such as Hall sensors and NMR probes. A conduction-cooled superconducting magnet for Hall sensor calibration has been designed with the center field of 7 T and the warm bore with the diameter of 50 mm. The superconducting magnet consists of six NbTi superconducting coils. The homogeneity of magnetic field is designed with 80 ppm (parts per million) in diameter of spherical volume (DSV) of 25 mm. A GM cryocooler with 1.5 W @4.2 K is employed to cool down the system. The design, fabrication, and testing of the superconducting magnet are reported in this paper.

A split superconducting magnet with large crossing warm bore of 150 and 50 mm is presented for material processing applications. Features of the magnet are characterized by a crossing warm bore and helium-free cryogenics. The magnet is configured in three pairs of split coils with pair separation of 85 mm to accommodate horizontal access. The magnet will be assembled after fabrications of two Nb3Sn and four NbTi coils. The maximum field in the inner Nb 3Sn coils exceeds 10 T when the center magnetic field is 8 T. Magnetic structures are optimized to acquire the maximum operation margin in a dynamic temperature range around liquid helium temperature. The quench protection of the magnet is analyzed in detail to release the 1.35-MJ magnetic energy safely. Finally, magnet cryogenics is presented and discussed.

Nb 3 Al is one of the most promising superconductors to replace Nb 3 Sn in large scale, high field superconducting magnet. Since the complicated conductor manufacturing process, long and stable Nb 3 Al conductor is difficult to acquire in a commercial scale. Based on a 70 m length of Nb–Al precursor conductor, we designed and fabricated a Nb 3 Al coil. The coil winding, low temperature diffusion heat treatment and epoxy impregnation are described in detail. The finished Nb 3 Al coil is tested as an insert in a background magnet. The test is performed at the background field from 7 T to 15 T. The test results are analyzed and presented in this paper.

A 9.4-T whole-body MRI superconducting magnet system is being manufactured in the Institute of Electrical Engineering, Chinese Academy of Sciences. The main magnet is an assembly of several coaxial coils. In this paper, three full-size dummy copper coils were wound and assembled to prove the coil's winding technology. A cryogenic experiment of the assembly was carried out by putting it into a liquid nitrogen container and testing the cryogenic mechanical properties and the electrical insulation performance. The winding and assembly process, testing apparatus, experimental procedure, and testing results of the dummy coils are discussed. The results show that the thermal contraction rates of the coils in axial and radial directions agree with the calculated results. The electrical insulation performance of the coils in cryogenic environment also meets the requirements.

C-axis textured SiC ceramics were prepared by a strong magnetic field of 6 T assisted gel-casting and subsequent pressureless sintering. The optimal suspension parameters for gel-casting were determined by analyzing the influences of pH value and dispersant content on the stability and dispersibility of suspensions. The effect of sintering conditions on the texture development and properties of SiC ceramics was discussed. It was found that the increasing sintering temperature or holding time promoted the densification process of SiC ceramics. The c-axis of SiC grain was aligned parallel to the magnetic field by applying a strong magnetic field of 6 T. The degree of texture of SiC ceramics showed a slightly increasing trend with the increase of sintering temperature or holding time. When the samples were sintered at 1950 °C for 4 h or 6 h, the large elongated grains were formed in the samples, leading to the extremely evident anisotropic microstructure on different planes. Textured SiC ceramics exhibited the anisotropic bending strength.

In this paper, we establish a novel sintering protocol for ex-situ MgB2 bulk in an open system by using Mg vapor. The Mg vapor successfully restrains both the continues oxidation and decomposition of MgB2, even after 96 h at 900°C. Such robust protection given to the ex-situ MgB2 bulk at high temperature provides the possibility of improving the superconducting connectivity and critical current density (Jc) using long-term sintering at high temperatures. The effect of sintering time on phase formation, microstructure, superconducting properties, and the mechanical properties of ex-situ MgB2 bulk are systematically investigated. A comparison of our novel protocol and the most successful ex-situ MgB2 bulk sintering process—the powder-in-closed-tube method (PICT)—is also discussed. Our novel protocol can improve superconducting properties to the same level as with the PICT method but allows MgB2 bulk to be used in an open system. This makes dealing with ex-situ MgB2 bulk for engineering applications feasible.

Polycrystalline CoFe 2 O 4 thin films were deposited on Si (100) substrates by chemical solution deposition with and without magnetic annealing. Magnetic field directions were applied parallel and perpendicular to the film surface during the magnetic annealing process. The variations of strain, microstructure and magnetic anisotropy of the films caused by the magnetic annealing are investigated. The results show that the film densification is promoted and grain morphology is changed by the magnetic annealing, which can be attributed to the promoting effect of magnetization force on the grain growing and grain boundary diffusing. Magnetic measurements indicate the enhancement of anisotropy and saturation magnetizations of the polycrystalline CoFe 2 O 4 after magnetic annealing. Furthermore, the rotation of easy axis along the field direction, the increased occupation of Co 2+ ions at B sites and the additional strain induced by the magnetic field are considered as the main reasons of the increased magnetic anisotropy.

The textured porous Al2O3 ceramics were prepared by slip casting in a strong magnetic field of 6 T and subsequently sintering. The c axis of Al2O3 grain was oriented parallel to the direction of the magnetic field and the textured porous microstructure with plate-shape grains was formed. The porosity of textured porous Al2O3 ceramic was 30.37% and the relative density reached 66.29% when the sintering temperature is 1600°C. The textured porous Al2O3 green body showed the linear shrinkage anisotropy. The bending strength of the textured porous Al2O3 ceramics depended on the alignment direction of plate-shape grains.

A NbTi superconducting joint technology applied for MRI/NMR has been developed with a cold-pressing method. The plastic deformation microstructure of the fabricated joint was investigated by using scanning electron microscopy and optical mi- croscope. The joint resistances were tested using coil current decay method. The contact resistance properties of the superconducting joint were investigated. The evolution of plastic deforming and the electrical contact characteristics of the NbTi superconducting joint are discussed. It is believed that the contact resistance is composed of constriction resistance and film resistance. With the pressure increasing, the dominant factor is changed from the film resistance to the constriction resistance. Finally, the joint resistance is inversely proportional to the cubic root of applied pressure. The joint resistance correlates with the increase in plastic deformation with increased pressure.

There are very strong requirements for the magnets with very high magnetic field for experimental facilities used in the new generations of special material processing devices. A high magnetic field superconducting magnet has been designed with the center field of 8 T, warm bore of 100 mm, and warm split-gap of 100 mm. The maximum magnetic field in the superconducting winding is about 11 T. Two GM cryocoolers are employed to cool down the system. The magnet consists of two high temperature superconducting coils with commercially available Bi-2223 tapes and six NbTi superconducting coils. There is very strong attractive force between the split-pairs coils. The design, fabrication and test of the superconducting magnet are reported in this paper.

A NbTi superconducting magnet with long-length uniform axial field is designed and will be fabricated for high-frequency gyrotron experiments. The magnet has a warm bore of 90 mm in diameter and a uniform axial field length of 200 mm. The magnetic field on the 200-mm axial length is adjustable from 0 to 9.2 T, accommodating a wide range of gyrotron experiment frequencies. The magnet is composed of ten coaxial NbTi coils connected in series. Optimization of the field configuration is carried out to obtain the magnet parameters. Cryogenics of the magnet system is adopted as conduction cooling with a single GM cryocooler. The magnet design and integration are presented in this paper.

A spherical superconducting rotor is spinning at low temperature of 4.2 K. The electromagnetic field generated by the stator coils engenders driving torque on the superconducting rotor through the window on the window side wall. The driving torque at different rotation position was calculated by using finite element analysis (FEA). The results show that the driving torque is changed periodically when the rotor rotates every one quarter revolution. Based on the calculation results, this paper describes an approach to design higher efficient driving method which reduces the number of the window position patterns from eight to four and adds more driving ranges to increase driving toque. As a results, the value of driving acceleration of the rotor using this improved driving method is increased 4.58% compared with the original method with the driving current of 50 A. The rotation experiment is performed. It will be helpful to improve the acceleration efficiency of the spherical superconducting rotor.

In this paper, the textured Si3N4 ceramics were prepared by adding seed particles during gel-casting in the magnetic field of 6 T, followed by pressureless sintering. The effect of pH on the stability and dispersibility of Si3N4 slurry and the effect of seed particles content on texture formation of Si3N4 ceramics were both studied. Those results showed that the slurry with good stability and dispersibility was obtained when pH was about 11.6. The a or b-axis of Si3N4 particles or crystals was aligned parallel to the direction of the magnetic field in the magnetic field of 6 T. The degree of texture of Si3N4 ceramics further increased during sintering. With the increasing of additional β-Si3N4 particles in the magnetic field of 6 T, the degree of texture increased from 0.19 without seed particles to 0.76 with 9% (mass fraction) seed particles. The increase of seed particles content promoted the texture formation of Si3N4 ceramics.

A 9.4-T/800-mm superconducting magnet for whole-body magnetic resonance imaging system has been designed and will be constructed from NbTi conductors. Main coils wound on five aluminum alloy formers provide the center field strength of about 9.4 T. In addition, compensation coils wound on another aluminum alloy former are used to improve the field uniformity of the imaging region. The operating point of the inner main coil is very close to the critical properties of its wire, and its temperature margin is about 0.4 K. It is necessary to know the mechanical stress in the main coils during all operating conditions. The mechanical behavior of the main coils during winding, cooldown, and energizing is analyzed. The effects on mechanical disturbances are predicted, and one available method is proposed to reduce premature quench. In addition, the dimension variations and position changes due to pretension, thermal contraction, and magnetic compression are present.

A conduction-cooled superconducting split magnet system with large crossing warm bore has been successfully constructed in our laboratory for material processing applications. The magnet system design was described in a previous paper. The magnet is composed of six NbTi low temperature superconducting coils, which generate 5.5-T central magnetic field and two Bi2223/Ag high temperature superconducting (HTS) insert coils, which generate 2.5-T central magnetic field and assembled in the form of split coil groups. The magnet has a 136-mm split gap to accommodate the crossing warm bore of 100 mm in diameter. The magnet system is cooled by two GM cryocoolers. The initial cooldown takes 9.2 days and the final temperature of the magnet is about 4.0 K. The HTS coils and NbTi coils are to be operated in the driven mode with two independent power supplies, under the operating currents of 200 A (HTS) and 139 A (NbTi), respectively. The magnet is successfully powered up to 8 T with a the ramp time of 290 min. In this paper, the fabrication and test of the superconducting split magnet system are presented.

The aim of this paper is to design a torque compensation system with guaranteed performance that allows attitude control of the superconducting rotor, which is spinning at 4.2 K. The torque compensation system includes four pairs of torque-producing superconducting coils. The torques generated by the torque-producing coils are calculated using numerical analysis method. This paper presents an approach to design a torque compensation system that is used to erect the rotor prior to and during spinup, and then is also used to develop error compensation torques.

The oscillating heat pipe (OHP) with high thermal performance and easy manufacturing has been increasingly studied in the recent years. In this paper, the OHP for cryogenic application is investigated. An OHP system is manufactured with 3 sections of evaporator, condenser and adiabatic section. The temperature of evaporator and condenser and the gas pressure of the OHP are measured. The experiments with working fluid of nitrogen are carried out. When the heat input increases, the temperature and pressure increases were observed experimentally. When the dry-out takes place, the evaporator temperature rises quickly, the gas pressure drops sharply and the amplitude of the pressure oscillation reduces largely. The effective thermal conductivity is obtained and compared to other literatures. The relation between the effective thermal conductivity and the gravity, and the relation between the gas pressure and the gravity are attempted to interpret. The cryogenic OHP system shows much higher thermal performance than high purity metal, and it requires more study on the geometric optimization, the selection of working fluid and the operating limitations.