Strong Pulsed Magnetic Fields Research Articles

Development of Multi-Part Field-Shapers for Magnetic Pulse Welding Using Nanostructured Cu-Nb Composite

Magnetic pulse welding (MPW) employs a strong pulsed magnetic field to accelerate parts against each other, thus forming an impact joint. Single-turn tool coils and field-shapers (FSs) used in MPW operate under the most demanding conditions, such as magnetic fields of 40–50 T with periods lasting tens of microseconds. With the use of conventional copper and bronze coils, intense thermo-mechanical stresses lead to the rapid degradation of the working bore. This work aimed to improve the efficiency of field-shapers and focused on the development of two- and four-slit FSs with a nanocomposite Cu 18Nb brazed wire acting as an inner current-carrying layer. The measured ratios of the magnetic field to the discharge current were 56.3 and 50.6 T/MA for the two- and four-slit FSs, respectively. FEM calculations of the magnetic field generated showed variations of 6–9% and 3% for the two- and four-slit FSs, respectively. The ovality percentages following copper tube compression were 27% and 7% for the two- and four-slit FSs, respectively. The measured deviations in the weld-joining length were 11% and 1.4% in the two- and four-slit FSs, respectively. Compared to the previous experiments on an entirely steel inductor, the novel FS showed significantly better results in terms of its efficiency and the homogeneity of its magnetic field.

Driving Inertial Confinement Fusion With Strong Pulsed Magnetic Field

Regarding inertial confinement fusion (ICF), the current proposed driving energy sources are mainly laser beams or high-energy particle beams. This paper proposes a new method: Adopting a strong pulsed magnetic field as the driving energy source, explored its action principle, derived all relevant formulas, calculated an example and compared it with existing driving methods.The conclusion drawn is that this method can achieve high energy gain, the required equipment is relatively simple and without the disadvantages of other methods, making it a feasible method.

Unusual metallic state in superconducting A15-type La4H23

ABSTRACT Hydride superconductors continue to fascinate the communities of condensed matter physics and material scientists because they host the promising near room-temperature superconductivity. Current research has concentrated on the new hydride superconductors with the enhancement of the superconducting transition temperature (Tc). The multiple extreme conditions (high pressure/temperature and magnetic field) will introduce new insights into hydride superconductors. The study of transport properties under very high magnetic fields facilitates the understanding of superconductivity in conventional hydride superconductors. In the present work, we report experimental evidence of an unusual metal state in a newly synthesized cubic A15-type La4H23 that exhibits superconductivity with a Tc reaching 105 K at 118 GPa. A large negative magnetoresistance is observed in strong pulsed magnetic fields in the non-superconducting state of this compound below 40 K. Moreover, we construct the full magnetic phase diagram of La4H23 up to 68 T at high pressure. The present work reveals anomalous electronic structural properties of A15-La4H23 under high magnetic fields, and therefore has great importance with regard to advancing the understanding of quantum transport behaviors in hydride superconductors.

Transcranial Magnetic Stimulation-induced Mania: A Risk Worth Taking?

Introduction In the context of treatment-resistant bipolar depression, the use of neuromodulation techniques, notably transcranial magnetic stimulation (TMS), has been on the rise, particularly in the treatment of mood disorders. TMS involves the generation of a strong pulsed magnetic field through an electromagnet placed near the skull, thereby inducing an electrical field capable of depolarizing nerve cell membranes (Dolberg et al., 2001). The magnetic nature of TMS carries advantages compared to direct electric stimulation, such as fewer side effects, reduced invasiveness, and precise targeting. Nevertheless, it is not without its risks. Reported concerns include the induction of manic or hypomanic states, particularly in individuals with bipolar disorder, as well as unipolar depression (Sakkas et al., 2003; Ozten et al.,2013; Knox et al 2021).Objectives This review aims to assess the safety and viability of TMS as a therapeutic option and how to best optimize its clinical use.MethodsA comprehensive literature review was conducted utilizing resources from Pubmed, Researchgate, and Google Scholar.ResultsDespite some inconsistencies and potential confounding factors, our findings suggest that TMS may not significantly elevate the risk of manic switching, especially when compared to conventional treatments like antidepressants. However, it may potentially induce manic episodes, particularly when used as monotherapy or in combination with other treatments. Variables such as treatment protocol and prior response to medication may contribute to mood switching risk. Proposed safety measures include personalized protocol design, close patient monitoring and the combination with mood-stabilizing medication.ConclusionsTranscranial magnetic stimulation has been associated with manic and hypomanic episodes in mood disorder patients. While the evidence remains limited, it appears that certain individuals may be more susceptible to mood switching. Nevertheless, further research is needed to better elucidate variables influencing mood switching during TMS treatment and to develop effective preventative measures, especially for patients already predisposed to manic switching.Disclosure of InterestNone Declared

Снижение механических напряжений в тонкостенной квазибессиловой магнитной системе, внесенной во внешние скрещенные магнитные поля

The mechanical stresses in the thin-walled quasi-force-free winding of the solenoid, which arise when a strong pulsed magnetic field is produced, can be significantly reduced if the winding is inserted into the area between two magnets creating crossed fields. It is shown that with a rational choice of the amplitude and shape of the external fields pulses the stresses can be reduced to values less than one tenth of the magnetic pressure of the generated field.

The mechanical stresses reduction in a thin-walled quasi-force-free magnetic system inserted into external crossed magnetic fields

The mechanical stresses in the thin-walled quasi-force-free winding of the solenoid, which arise when a strong pulsed magnetic field is produced, can be significantly reduced if the winding is inserted into the space between two magnets creating crossed fields. It is shown that, with a rational choice of the amplitude and shape of the external field pulses, the stresses can be reduced to values less than one tenth of the magnetic pressure of the generated field. Keywords: strong magnetic fields, quasi-force-free field, force-balanced coil.

Brittle fracture of a conductor in a strong pulsed magnetic field

The main factors resulting in conductor failure under the action of a strong pulsed magnetic field are analyzed. The theoretical model describes the geometry of a cylindrical thick-walled solenoid and considers magnetic field diffusion, ohmic heating of the material and mechanical stresses arising in it. The magnetic field amplitude at which induced stresses in the material reach the von Mises yield criterion is used as the Bth threshold field separating the areas of safe (non-destructive) and dangerous fields. In the case of an initially uniform material, the maximum heating temperature corresponding to this limit, which predetermines the thermomechanical stress, has been derived analytically. In the general case, based on the analysis of the calculated threshold field, the influence of various parameters (magnetic pulse characteristics, elastic moduli of the material, etc.) on the conductor resistance in the pulsed magnetic field is studied and ways of increasing the threshold field are proposed, in particular, by using different spatial profiles of the initial resistivity. It is shown that in comparison with a uniform material, a modified layer with increased resistivity formed on the surface allows to significantly increase the amplitude of the magnetic pulse withstood by the material without fracture. Keywords: Magnetic field diffusion, plastic deformation, thermomechanical stress, yield strength, von Mises yield criterion.

Elastic-plastic deformations of single-turn solenoid under cyclic effects of a strong pulsed magnetic field

The processes of destruction of a monolithic single-turn solenoid with multiple generation of pulses of a strong magnetic field with an amplitude of 15- 40 T are considered. Based on models of the electromagnetic field and elastic-plastic deformation in a continuous medium, two modes of destruction during the cyclic process of generating pulses of a strong magnetic field are investigated: accumulation of residual deformation and low-cycle fatigue in the surface layer of the conductor. It is shown that both mechanisms of destruction act simultaneously. At the same time, the first of them limits the resource of the inductor at the level of hundreds of pulses. The destruction by the mechanism of low-cycle fatigue becomes the main factor limiting the inductor's life in the case of oscillatory magnetic field pulses with relatively small attenuation at induction amplitudes below 20 T. The resource of the product in this case is estimated within 103-104 pulses.

Хрупкое разрушение проводника в сильном импульсном магнитном поле

The main factors resulting in conductor failure under the action of a strong pulsed magnetic field are analyzed. The theoretical model describes the geometry of a cylindrical thick-walled solenoid and considers magnetic field diffusion, ohmic heating of the material and mechanical stresses arising in it. The magnetic field amplitude at which induced stresses in the material reach the von Mises yield criterion is used as the Bth threshold field separating the areas of safe (non-destructive) and dangerous fields. In the case of an initially uniform material, the maximum heating temperature corresponding to this limit, which predetermines the thermomechanical stress, has been derived analytically. In the general case, based on the analysis of the calculated threshold field, the influence of various parameters (magnetic pulse characteristics, elastic moduli of the material, etc.) on the conductor resistance in the pulsed magnetic field is studied and ways of increasing the threshold field are proposed, in particular, by using different spatial profiles of the initial resistivity. It is shown that in comparison with a uniform material, a modified layer with increased resistivity formed on the surface allows to significantly increase the amplitude of the magnetic pulse withstood by the material without fracture.

Effect of Magnetic Impurities on Superconductivity in LaH10.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications. On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH10 , encounters a serious complication because of the large upper critical magnetic field HC2 (0), exceeding 120-160T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH10 : each at% of Nd causes a decrease in TC by 10-11K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H10 demonstrates completely linear HC2 (T)∝|T -TC |, which calls into question the applicability of the Werthamer-Helfand-Hohenberg model for polyhydrides. The suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of TC with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson's theorem gives new experimental evidence of the isotropic (s-wave) character of conventional electron-phonon pairing in lanthanum decahydride.

TMS-Like Magnetic Fields Modulate Metabolic Activity of Hepatic and Colorectal Cancer Cells

Transcranial magnetic stimulation (TMS) is a widely available technology employing relatively strong (up to 4 T) pulsed (up to 300 Hz) magnetic fields for diagnostics of brain functions and treatment of various brain disorders. The current paradigm implies that the magnetic induction of Eddy currents in the brain neurons is the leading biological mechanism of TMS. At the same time, it is almost unknown how the TMS-like magnetic fields act on nonneuronal cells. Here, we explored the effects of TMS-like repetitive magnetic stimulation (RMS) on metabolic activity of human colorectal cancer (CRC) and hepatocellular carcinoma (HCC) cells. The HCT116 (CRC) and HuH7 (HCC) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> cell cultures were treated using a TMS device “Magstim Rapid <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ” with an air-cooled “Magstim” figure-eight coil (AFC70). Five intermittent RMS (iRMS) and two burst RMS (bRMS) experimental protocols were applied to the monolayers of the cells as a single treatment session. The activity of succinate dehydrogenase, an enzyme essential for energy production in mitochondria, was measured by 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric viability assay in 24 h post-stimulation. Compared to untreated control, in HCT116 cells, a low-frequency iRMS treatment ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f $ </tex-math></inline-formula> = 1 Hz, 600 pulses, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B $ </tex-math></inline-formula> = 0.8 T) induced a statistically significant decrease in metabolic activity (viability), while the high-frequency iRMS and bRMS increased it. In HuH7 cells, all tested RMS protocols either did not change or stimulated the metabolic activity (viability) of the cells, in comparison to the untreated control. The analysis of correlations revealed the almost opposite trends in CRC and HCC cells response to the frequency, temporal patterns, and magnetic field flux density considered as the parameters of the experimental RMS. Our findings demonstrate the tumor type- and stimulation protocol-specific effects of the repurposed TMS technology on colorectal and liver cancer cells. The underlying mechanism of these differences requires further study. The current results indicate that TMS-like magnetic fields may have new potential applications as an adjuvant anticancer treatment modality.

Dual-Functional Wireless Power Transfer and Data Communication Design for Micromedical Implants

Smart microimplants are playing increasing roles in modern medicine. Wireless power transfer (WPT) and data communication are essential components in microimplants. In order to minimize device size, a preferred design is to share the wireless power channel with the data communication links consisting of a downlink and an uplink. While the implementation of the downlink is relatively easy, the uplink from the implant to the external unit is difficult to implement due to the limited power supply and small transceiver coil available within the implant. In this work, we present a new design of the data uplink that utilizes a special tapped coil and a simple passive circuit to produce a strong pulsed magnetic field (PMF) for signal emission. The strong PMF, which is oscillatory at the same resonant frequency as the WPT carrier, allows wireless data transmission over a longer distance through the WPT channel. Our new design is studied analytically, and the function of our circuit is confirmed by a computer simulation. A prototype is constructed, and its performance is compared with the existing load shift keying (LSK) method. Our experimental result showed that the design produced more than 15 times stronger signal strength at the receiving end.

Martensitic transformation in the systems based on Fe-Ni compositions in strong pulsed magnetic fields

Purpose of work. To ascertain the causes of the abnormally large displacement of the martensitic point in steels and iron alloys in strong pulsed magnetic fields at low temperatures. Research methods. Generalization of experimental and theoretical investigations of the strong magnetic field influence on the martensitic transformation in steels and iron alloys, taking into account the magnetic state of austenite. The obtained results. The distributions of the martensitic point displacement ΔMS from the content of the main component - iron and the temperature of the martensitic γ → α- transformation beginning (martensitic point MS) in different experiments are obtained. It is shown that the obtained temperature dependence ΔMS(MS) in a strong magnetic field at low temperatures decomposes into two components, one of which correlates with the generalized Clapeyron-Clausius equations, and the other is opposite to it. In addition, it was found that steels and alloys with intense γ → α- transformation in a magnetic field contain at least 72.5% iron (wt), which at low temperatures in the fcc structure is antiferromagnetic. Scientific novelty. The anomalous temperature dependence of the distribution ΔMS(MS) in a strong magnetic field is explained on the basis of quantum representations of the magnetic interaction of atoms in the Fe-Ni system. This effect is associated with a number of other invar effects, in particular, with an abnormally large spontaneous and forced magnetostriction, a strong dependence of the resulting exchange integral on the interatomic distance. The point of view according to which in these alloys in a magnetic field γ → α- transformation occurs by the type of “magnetic first kind phase transformation” is substantiated. It is assumed that the nucleation of the martensitic phase in a magnetic field occurs in (at) local regions of γ- phase with disoriented atomic magnetic moments (with high compression and increased forced magnetostriction). Practical value. The information obtained in this work provides grounds for explaining the kinetic features of the transformation of austenite into martensite in steels and iron alloys.

Piezomagnetic switching and complex phase equilibria in uranium dioxide

Actinide materials exhibit strong spin–lattice coupling and electronic correlations, and are predicted to host new emerging ground states. One example is piezomagnetism and magneto-elastic memory effect in the antiferromagnetic Mott-Hubbard insulator uranium dioxide, though its microscopic nature is under debate. Here, we report X-ray diffraction studies of oriented uranium dioxide crystals under strong pulsed magnetic fields. In the antiferromagnetic state a [888] Bragg diffraction peak follows the bulk magnetostriction that expands under magnetic fields. Upon reversal of the field the expansion turns to contraction, before the [888] peak follows the switching effect and piezomagnetic ‘butterfly’ behaviour, characteristic of two structures connected by time reversal symmetry. An unexpected splitting of the [888] peak is observed, indicating the simultaneous presence of time-reversed domains of the 3-k structure and a complex magnetic-field-induced evolution of the microstructure. These findings open the door for a microscopic understanding of the piezomagnetism and magnetic coupling across strong magneto-elastic interactions.

Behavioural responses in the sand tiger shark (Carcharias taurus) to permanent magnets and pulsed magnetic fields

ABSTRACT Sharks are threatened by several human activities that impact their distribution and abundance. A great proportion of shark captures happen as incidental capture (bycatch) by fisheries and in beach nets. Recent studies have focused on reducing these captures by exploiting technologies that target the sharks’ electrosensory system, obtaining contrasting results. This study investigates the effect of a strong neodymium magnet and pulsed magnetic fields (PMFs) on captive sand tiger sharks (Carcharias taurus) through the analysis of their behavioural responses. Firstly, individuals were presented with the magnet in combination with different types of food. The magnet did not influence the sharks’ behaviours, while an effect of the food type emerged. Secondly, PMFs were generated through a pulsed electric current induced within a solenoid associated with a PVC structure. The PMFs affected some of the sharks’ behaviours, both near (<2 m) and at a distance (>2 m) from the source. The results suggest that strong magnets are inefficient in deterring sand tiger sharks, while PMFs could be a promising alternative. This study confirms how the efficacy of shark repellents may be affected by factors such as the type of electrosensory stimuli, the species involved, and the context in which the interaction takes place.

Destruction of Ferruginous Quartzite in Rock Mass by High-Gradient Magnetic Fields

The results of experimental and theoretical studies of the applicability of strong pulsed magnetic fields to destruct ferruginous quartzite are presented. A “magnetokinetic” model of ferruginous quartzite destruction, based on the interaction of magnetite grains with quartz matrix at the passage of a high-gradient electromagnetic pulse through rock, is proposed. It is shown that the high-gradient pulsed magnetic field can be used to destruct quartz-containing rocks in a massif during both drilling and blasting and when solving geoenvironmental problems in mining crystalline rocks, complex-structure massifs of ferruginous quartzites by the example of deposits of the Kursk magnetic anomaly (KMA) and others.

Size effects in the formation of an uncompensated ferromagnetic moment in NiO nanoparticles

The magnetic properties of samples of NiO nanoparticles with average sizes of 23, 8.5, and 4.5 nm were investigated. Using the magnetization curves measured in strong (up to 250 kOe) pulsed magnetic fields, the contributions of the free spin and ferromagnetic subsystems were extracted. It has been found that the ferromagnetic contribution increases with a decrease in the nanoparticle size and is proportional to the fraction of uncompensated exchange-coupled spins. It is demonstrated that the uncompensated spins form in the antiferromagnetic NiO oxide due to an increase in the fraction of surface atoms in the nanoparticles with decreasing particle size and defects in the bulk of particles.

Discharge current enhancement in inertial electrostatic confinement fusion by impulse high magnetic field

Effect of strong pulsed magnetic field on the discharge behavior of a cylindrical inertial electrostatic (IEC) device has been investigated both theoretically and experimentally. By applying strong pulsed magnetic field in a new fabricated miniature cylindrical IEC device equipped with Inductively Coupled Plasma (ICP), discharge current amplifications were observed at ordinary pressures as well as low pressure ICP-assisted operational regime with deuterium gas. The obtained results indicate the evidence for significant amplification of discharge current up to more than one hundred times. Since the neutron production rate has been previously proven to be linearly dependent on the discharge current, then this study might open new investigations for probable increment of fusion reaction rates in IEC devices with additional strong magnetic field.

Lithium Speciation in the LiPF6/PC Electrolyte Studied by Two-Dimensional Heteronuclear Overhauser Enhancement and Pulse-Field Gradient Diffusometry NMR

Electrolytic dissociation of lithium hexafluorophosphate (LiPF6) in the nonaqueous cyclic propylene carbonate (PC) has been investigated in the wide range of concentration (0.05–3.5 M) by 7Li solution-state nuclear magnetic resonance (NMR) spectroscopy. Two-dimensional heteronuclear Overhauser enhancement spectroscopy NMR experiments have not only enabled the cation solvation and ion-pairing to be directly monitored but additionally evidence anion–solvent interaction at higher concentrations (>1.2 M) of the PC electrolyte. Preliminary analysis of kinetic nOe data has been made to determine site-dependent cross-relaxation rates for the spatial interaction of the solvent with the Li+ cation and the PF6– anion. The concentration dependence of the 7Li NMR self-diffusion coefficient (Dself), determined using very strong pulsed magnetic field gradients (∼1700 Gauss/cm), depicts two breaks to mark the solvation and ion-pairing events in a distinct manner. This in turn has aided the determination of solvent coordination number and average sizes of solvated and ion-paired clusters. Our results indicate that in the contact ion pair (CIP)-dominated electrolyte (>2 M), lithium-ion mobility across the solvated and ion-paired environments appears to be inhibited which makes the spectral distinction of solvated and ion-paired environments possible. The concentration dependence of the 7Li NMR spectral and diffusometry data is in striking correspondence with that of bulk conductivity measurements and point to the detrimental effect of CIP aggregates in impeding the ionic conductivity at high salt concentrations. These results have significance in understanding the structure and dynamics of lithium-ion solvates that are ubiquitous in the working environment of a lithium-ion battery.

Study of Measurement Techniques for Strong Pulsed Magnetic Field

Background: Currently, how to measure the magnetic field accurately is a difficulty in the study of strong magnetic field. Methods: This paper summarizes several methods of measurement techniques for strong pulsed magnetic field presently, the principles and characteristics of various measurement methods are compared and analyzed. The maximum measurement intensity of electromagnetic induction method can reach 103T. The magneto-optical effect method of Faraday can measure the magnetic field intensity of 0.1~10T, and the measurement error is within 10-2T. Results: The MOKE effect can measure a magnetic field intensity up to 100T, with an error 3×10-2T. The Zeeman effect can be measured in a magnetic field intensity of 1~20T. Conclusion: The existential problems of various methods are described. Lastly, some solutions are proposed according to the existential problems, and the development of measurement techniques for strong pulsed magnetic field in the future is prospected.