Compact Coil Research Articles

On the Development of Compact HTS Coil Modules for Large Bore High Field Superconducting Magnets

On the Development of Compact HTS Coil Modules for Large Bore High Field Superconducting Magnets

An arabinan from Citrus grandis fruits alleviates ischemia/reperfusion-induced myocardial cell apoptosis via the Nrf2/Keap1 and IRE1/GRP78 signaling pathways

Citrus grandis fruit is a famous traditional Chinese medicine with various bioactivities, including cardioprotective effects. Polysaccharides are one of the key active ingredients responsible for its cardioprotective effects. This study aimed to investigate the structure and cardioprotective effect of a homogeneous polysaccharide from C. grandis fruit (CGP80-1) and explore its mechanism against myocardial ischemia-reperfusion (MI/R) injury. Structure analysis showed that CGP80-1 (11,917 Da) is an arabinan with compact coil chain conformation, containing →5)-α-L-Araf-(1→, →3,5)-α-L-Araf-(1→, and →2,3,5)-α-L-Araf-(1→ as the backbone, as well as →5)-α-L-Araf-(1→ and t-α-L-Araf as side-chains substituted at the C2 and C3 positions. Pharmacological experiments showed that pre-treatment with CGP80-1 could effectively alleviate MI/R injury by improving endogenous antioxidant enzymes and cardiac enzymes, reducing reactive oxygen species levels, and regulating apoptosis-related proteins such as caspase-3, Bax, and Bcl-2. The protective effects were correlated with the Nrf2/Keap1 and IRE1/GRP78 signaling pathways. Further analysis of structure-activity relationships revealed that the myocardial protection effects of CGP80-1 might be attributed to its appropriate molecular weight, high arabinose content, and unique compact coil chain conformation. Overall, our results provide insight into the chemical structure of CGP80-1 and its mechanism of action, suggesting that CGP80-1 could be a candidate drug for myocardial protection.

Key Technologies in Developing Chip-Scale Hot Atomic Devices for Precision Quantum Metrology.

Chip-scale devices harnessing the interaction between hot atomic ensembles and light are pushing the boundaries of precision measurement techniques into unprecedented territory. These advancements enable the realization of super-sensitive, miniaturized sensing instruments for measuring various physical parameters. The evolution of this field is propelled by a suite of sophisticated components, including miniaturized single-mode lasers, microfabricated alkali atom vapor cells, compact coil systems, scaled-down heating systems, and the application of cutting-edge micro-electro-mechanical system (MEMS) technologies. This review delves into the essential technologies needed to develop chip-scale hot atomic devices for quantum metrology, providing a comparative analysis of each technology's features. Concluding with a forward-looking perspective, this review discusses the future potential of chip-scale hot atomic devices and the critical technologies that will drive their advancement.

Magnetic-field coils for metastability-exchange optical pumping, spectroscopy, and magnetic resonance of helium.

Optical pumping on the 23S-23P transition (1083nm) of metastable 3He or 4He atoms is used for science and applications. Gas is usually enclosed in elongated cells with lengths ranging from several centimeters to several meters for efficient absorption. Good magnetic-field homogeneity is needed for weak diffusion-induced relaxation and long nuclear magnetic resonance (NMR) signal lifetimes. A compact coil system is designed using a target-oriented numerical optimization method. It provides a suitably uniform field over cell volumes, with characteristics depending on the chosen optimization parameters. Additional pairs of coils can be used to generate transverse field components with contributions to the total field inhomogeneities that are discussed.

Minimizing Material Usage for Efficient and Compact Coil in Wireless Charging System of Electric Vehicles

Minimizing Material Usage for Efficient and Compact Coil in Wireless Charging System of Electric Vehicles

An ATP-free packaging of T4 DNA

Packaging of viral DNA into a capsid with liquid crystalline density is a crucial step in viral reproduction. DNA packaging with an adenosine triphosphate (ATP)-fueled molecular motor is an established viral DNA packaging mechanism system. On the other hand, DNA is compacted by the conformational change attributable to multivalent cations exclusively at valences higher than three. The conformational change of DNA was not considered as a mechanism of DNA packaging of viruses. Here, T4 DNA, ejected from a capsid in the ambient concentration of phosphate corresponding to the intra-cell concentration, is packaged into the capsid when the phosphate concentration decreases to the extra-cell concentration in coexistence with divalent cations, that is, Ca2+ and Mg2+. The compaction and packaging processes coincide with the conformational change of DNA. Divalent cations can compact T4 DNA when the counter anion is phosphate. The DNA-packaged and re-generated virions showed equivalent infective ability with the original populations. Fluorescent microscopy distinguished the conformational changes of DNA between compact forms and coil forms. Packaged or unpackaged DNA was confirmed enzymatically. Plaque-forming unit (Pfu) was used as the measure of infectious ability of virions. The concentration of ATP was measured by the luminometric method. The packaging process was proceeded in picomolar or lower concentration of ATP. This series of procedures may constitute a new ATP-free or low-ATP approach to packaging viral DNA with DNA conformational change underpinning the process. The results from this study may disclose an undiscovered facet of T4 life cycle.

A proof-of-concept Bitter-like HTS electromagnet fabricated from a silver-infiltrated (RE)BCO ceramic bulk

A novel concept for a compact high-field magnet coil is introduced. This is based on stacking slit annular discs cut from bulk rare-earth barium cuprate ((RE)BCO) ceramic in a Bitter-like architecture. Finite-element modelling shows that a small 20 turn stack (with a total coil volume of < 20 cm3) is capable of generating a central bore magnetic field of > 2 T at 77 K and > 20 T at 30 K. Unlike resistive Bitter magnets, the high-temperature superconducting (HTS) Bitter stack exhibits significant non-linear field behaviour during current ramping, caused by current filling proceeding from the inner radius outwards in each HTS layer. Practical proof-of-concept for this architecture was then demonstrated through fabricating an uninsulated four-turn prototype coil stack and operating this at 77 K. A maximum central field of 0.382 T was measured at 1.2 kA, with an accompanying 6.1 W of internal heat dissipation within the coil. Strong magnetic hysteresis behaviour was observed within the prototype coil, with ≈30% of the maximum central field still remaining trapped 45 min after the current had been removed. The coil was thermally stable during a 15 min hold at 1 kA, and survived thermal cycling to room temperature without noticeable deterioration in performance. A final test-to-destruction of the coil showed that the limiting weak point in the stack was growth-sector boundaries present in the original (RE)BCO bulk.

Compact metamaterial-inspired RF coil based on split-ring resonators to enhance the magnetic field for 1.5T magnetic resonance imaging

In this paper, we propose a metamaterial-inspired RF coil structure based on a multiple split-ring resonator (MSRR) for 1.5T MRI. An additional component that enables to enhance the magnetic field of RF coil is proposed. This novel component is incorporated an array of split-rings and a central feature combined with square and circular rings (SC). By aligning the component with the split-ring resonator (SRR) in a coplanar arrangement, we derive a compact MSRR equipped with the SC structure (SC MSRR). We analyze the effect of different numbers of split rings within the component and the distance from the feed coil on gain of the magnetic field. The results indicate that the proposed metamaterial-inspired structure can effectively improve the near-field properties of the coil. The proposed SC MSRR has enhanced B1− field strength effectively and keeps a lower specific absorption rate (SAR) level in the field of view (FOV), resulting in a significant increase in SAR efficiency and received sensitivity. Compared with the conventional SRR surface coil, the peak B1− field strength can be enhanced by 3.15 times in the case of using SC MSRR, the peak SAR can be reduced by 20.14 % and the peak SAR efficiency can be improved 3.60 times. In addition, the proposed 4-channel head array consisting of SC MSRRs efficiently generates a higher quality B1− field compared to the standard head birdcage coil. The high directivity of the metamaterial-inspired structure allows for good isolation between ports/channels. The high compactness and excellent performance of the SC MSRR prove that it can be an efficient candidate for the surface coil and high density array. This approach provides a new practical way to combine RF coils with metamaterials for MRI applications.

&lt;i&gt;Chaetoceros muelleri&lt;/i&gt; sulfated polysaccharides: chain conformation, physical characteristics, and morphology

&lt;p&gt;Increasing interest in biopolymers moves their knowledge frontiers. One area undergoing this development is polysaccharides. The practical and theoretical significance of studying polysaccharides lies in the numerous essential functions these macromolecules fulfill in living organisms, and the important industrial and technological purposes they serve. Polysaccharides are thought to be abundant in marine microalgae; nevertheless, little is known about their sulfated polysaccharides. We studied &lt;italic&gt;Chaetoceros muelleri&lt;/italic&gt; sulfated polysaccharide (CMSP) chain conformation, physical characteristics, and morphology. The CMSP spectrum generated from Fourier-transform infrared analysis displayed distinctive bands for these macromolecules. S=O and C–O–S signals were detected at 1225 and 820 cm&lt;sup&gt;−1&lt;/sup&gt;, respectively, confirming the presence of sulfate in the molecules. The biopolymer registered weight-average molar mass, intrinsic viscosity ([&lt;italic&gt;η&lt;/italic&gt;]), radius of gyration (RG), hydrodynamic radius (Rh), and sulfate degree of substitution of 1933 kDa, 577 mL/g, 62 nm, 44 nm, and 0.5 (sulfates per disaccharide repeat unit), respectively. The exponent α and the coefficient K in the Mark-Houwink-Sakurada (MHS) equation were 0.76 and 9.76 x 10&lt;sup&gt;−3&lt;/sup&gt; mL/g, respectively. These values suggest a flexible and compact random coil structure in CMSP. The sample's zeta potential (ζ), conductivity, and diffusion coefficient (D) were −26.43 mV, −2.07 µm cm/s V, 1.25 mS/cm, and 1.8 × 10&lt;sup&gt;−8&lt;/sup&gt; cm&lt;sup&gt;2&lt;/sup&gt;/s, correspondingly. The negative charge in the molecules is related to the sulfate groups contained. The CMSP surface was coarse and craggy, according to scanning electron microscopy (SEM). The information generated in this present study contributes to elucidating characteristics as fundamental knowledge to understand the macromolecule functionality.&lt;/p&gt;

A Simultaneous Power and Data Transfer Technology Using Dual-Resonance-Band Circuits for Domino-Resonator WPT Systems

The integrated transmission of power and data is a promising technology in various wireless power transfer (WPT) application scenarios. In this work, a novel simultaneous power and data transfer (SPDT) technology for domino-resonator WPT systems is proposed. The frequency shift keying (FSK) power modulation method is adopted in dual-resonance-band circuits to maintain high system transfer efficiency at two different frequencies. Considering the cross-coupling between nonadjacent resonators, the system operating frequencies shift slightly away from the circuit resonant frequencies, and the same constant output voltage (CV) characteristics can be always guaranteed with different data sequences. Subsequently, a compact coil structure is developed to accommodate the tight space constraint inside the insulator. Finally, aiming at the 35-kV suspension composite insulator with five embedded domino resonators, a 15W experimental prototype is built to realize simultaneous power and data transfer and constant voltage output. The experimental results show that the fluctuation of output voltage is less than 5%, and the overall system transfer efficiency is higher than 75%.

Screening-current-induced magnetic fields and strains in a compact REBCO coil in self field and background field

REBa2Cu3O7−x (REBCO) coated conductors, owing to its high tensile strength and current-carrying ability in a background field, are widely regarded a promising candidate in high-field applications. Despite the great potentials, recent studies have highlighted the challenges posed by screening currents, which are featured by a highly nonuniform current distribution in the superconducting layer. In this paper, we report a comprehensive study on the behaviors of screening currents in a compact REBCO coil, specifically the screening-current-induced magnetic fields and strains. Experiments were carried out in the self-generated magnetic field and a background field, respectively. In the self-field condition, the full hysteresis of the magnetic field was obtained by applying current sweeps with repeatedly reversed polarity, as the nominal center field reached 9.17 T with a maximum peak current of 350 A. In a background field of 23.15 T, the insert coil generated a center field of 4.17 T with an applied current of 170 A. Ultimately, a total center field of 32.58 T was achieved before quench. Both the sequential model and the coupled model considering the perpendicular field modification due to conductor deformation are applied. The comparative study shows that, for this coil, the electromagnetic–mechanical coupling plays a trivial role in self-field conditions up to 9 T. In contrast, with a high axial field dominated by the background field, the coupling effect has a stronger influence on the predicted current and strain distributions. Further discussions regarding the role of background field on the strains in the insert suggest potential design strategies to maximize the total center field.

Short-circuit protection scheme with efficient soft turn-off for power modules

With the increased current density of power semiconductor devices, their short-circuit reliability becomes a critical concern, especially prominent in SiC MOSFETs, exhibiting a much narrower short-circuit withstanding time. This paper proposes an effective protection scheme utilizing a compact PCB Rogowski coil to detect the short-circuit fault fast, and an active gate clamping circuit with a soft turn-off for protection. This scheme is first experimentally verified in discrete Si IGBT and SiC MOSFET, and subsequently in power modules for both. The results confirm its benefits in decreasing overshoot drain or collector voltage, peak current, and limiting short-circuit energy to avoid thermal runaway failure. Furthermore, the influence of key circuitry parameters in the soft turn-off circuit is investigated, and the general design methodology aiming for different devices is proposed.

Optical pumping enhancement of a free-induction-decay magnetometer

Spin preparation prior to a free-induction-decay (FID) measurement can be adversely affected by transverse bias fields, particularly in the geophysical field range. A strategy that enhances the spin polarization accumulated before readout is demonstrated, by synchronizing optical pumping with a magnetic field pulse that supersedes any transverse fields by over two orders of magnitude. The pulsed magnetic field is generated along the optical pumping axis using a compact electromagnetic coil pair encompassing a micro-electromechanical systems (MEMS) vapor cell. The coils also resistively heat the cesium vapor to the optimal atomic density without spurious magnetic field contributions as they are rapidly demagnetized to approximately zero field during spin readout. The demagnetization process is analyzed electronically, and directly with a FID measurement, to confirm that the residual magnetic field is minimal during detection. The sensitivity performance of this technique is compared to existing optical pumping modalities across a wide magnetic field range. A noise floor sensitivity of 238fT/Hz was achieved in a field of approximately 50 µT, in close agreement with the Cramér–Rao lower bound predicted noise density of 258fT/Hz.

20 T Hybrid Nb3Sn-HTS Block-Coil Accelerator Dipole With Stress-Management

In the framework of studies for high energy particle colliders, design concepts for high field dipoles are being explored. In particular, relatively compact 20 T magnets can be achieved in a hybrid configuration, combining a High Temperature Superconductor (HTS) and a Low Temperature Superconductor (LTS). Preliminary concepts have been previously proposed using Bi2212 for the HTS and Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn for the LTS. One of the main difficulties of 20 T magnets is the management of the very high stresses developing during operation. The design concepts rely on a rectangular block-coil layout, which offers the advantage of aligning the conductors with the main magnetic field, therefore submitting the conductors to a perpendicular electromagnetic force for a better control of the stresses. In addition, the layout allows a specific stress management, with adequate horizontal and vertical plates to intercept the stresses. The paper presents the improvements provided to the initial concept. In terms of magnetic design, the field quality has been improved. In terms of mechanical design, the stress management has been optimized to provide a compact coil with a reduced peak stress on the HTS. Concepts for flared-end coils with joints in the coil-ends are finally presented.

Design of new resonant magnetic perturbation coils on the J-TEXT tokamak

The resonant magnetic perturbation (RMP) system is a powerful auxiliary system on tokamaks. On the J-TEXT tokamak, a set of new in-vessel coils is designed to enhance the amplitude of the RMP. The new coils are designed to be two-turn saddle coils. These two-turn saddle coils have been optimized in terms of their structure, support, and protection components to overcome the limitations of the narrow in-vessel space, resulting in a compact coil module that can be accommodated in the vessel. To verify the feasibility of this design, an electromagnetic simulation is performed to investigate the electrical parameters and the generated field of the coils. A multi-field coupled simulation is performed to investigate the capacity of heat dissipation. As a result of these efforts, the new RMP coils have been successfully installed on the J-TEXT tokamak. It has significantly enhanced the RMP amplitude and been widely applied in experiments.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Attachable DC Coil Array for Improved Functional MRI at 7T

The prefrontal cortex (PFC) has long been concerned as an important part in cognitive control of neuroscience field. Functional magnetic resonance imaging (fMRI) has been introduced as an effective neuroimaging technique to explore neural activity. However, images within PFC region are subject to susceptibility artifacts, which give rise to undesired image distortion and signal drop-out. In this work, we proposed a method of adding a static magnetic field with high-order spatial pattern for artifact correction. Based on that, a compact attachable 8-channel coil array was constructed. Two toroid chokes were optimized and connected to each coil loop to minimize radiofrequency coupling. To evaluate the array performance, bench measurements and MRI experiments over phantoms and a human subject at 7T were conducted. With the proposed array applied, only 0.3 MHz and 1 MHz frequency shift were introduced to the RF coil, and no apparent RF performance change was observed; the inhomogeneity was reduced by 15%∼24%; in fMRI images over the human subject, “notorious” artifacts within target region were relatively mitigated. The present setup offers a feasible means for practical artifact correction, which is promising for the research that focuses on PFC regions.

Design of Compact Self-Shielded Uniform Magnetic Field Coils Based on Multipole Moment Optimization

Design of Compact Self-Shielded Uniform Magnetic Field Coils Based on Multipole Moment Optimization

Compact voice coil deformable mirror with high wavefront fitting precision

Compact voice coil deformable mirror with high wavefront fitting precision

Salt-Induced Transformations of Hybrid Micelles Formed by Anionic Surfactant and Poly(4-vinylpyridine).

Salt-induced structural transformation of charged hybrid surfactant/polymer micelles formed by potassium oleate and poly(4-vinylpyridine) was investigated by cryo-TEM, SANS with contrast variation, DLS, and 2D NOESY. Cryo-TEM data show, that at small salt concentration beads-on-string aggregates on polymer chains are formed. KCl induces the transformation of those aggregates into rods, which is due to the screening of the electrostatic repulsion between similarly charged beads by added salt. In a certain range of salt concentration, the beads-on-string aggregates coexist with the rodlike ones. In the presence of polymer, the sphere-to-rod transition occurs at higher salt concentration than in pure surfactant system indicating that hydrophobic polymer favors the spherical packing of potassium oleate molecules. The size of micelles was estimated by DLS. The rods that are formed in the hybrid system are much shorter than those in polymer-free surfactant solution suggesting the stabilization of the semi-spherical endcaps of the rods by embedded polymer. 2D NOESY data evidence that in the spherical aggregates the polymer penetrates deep into the core, whereas in tighter packed rodlike aggregates it is located mainly at core/corona interface. According to SANS with contrast variation, inside the rodlike aggregates the polymer adopts more compact coil conformation than in the beads-on-string aggregates. Such adaptive self-assembled polymer-surfactant nanoparticles with water-insoluble polymer are very promising for various applications including drag reduction at transportation of fluids.