Variable Magnetic Field Research Articles

Measuring local physical parameters in coronal loops with spatial seismology

Context. The method of spatial seismology can be applied to the amplitude profile of transverse coronal loop oscillations to constrain the distributions of physical parameters, such as the loop density, magnitude of the magnetic field, and so on. Aims. We intend to develop and apply a practical spatial seismology technique to detect physical parameters of plasma and validate its effectiveness by comparing it with other methods. Methods. A spatial seismology inversion was conducted by numerically optimizing a parametric dynamic model of the loop’s density stratification and magnetic field variation to best fit the measured amplitude profile of the loop. Results. The spatial seismology inversion technique developed here was applied to a transverse coronal loop oscillation that occurred on 2013 April 11, whose oscillation amplitude profile of both the fundamental mode and first overtone was reported in previous work. The consistency between the time domain analysis and spatial seismology has been verified. Meanwhile, we accounted for the asymmetric profile of the fundamental mode by forward modeling and we derived the magnetic field distribution by inverse modeling, which is coincident with that of the extrapolated one. In addition, spatial seismology inversion was applied to the transverse oscillation event on 2022 March 30 to obtain the distribution of the loop’s density and magnetic field, which are compared with the results derived from the differential emission measure (DEM) diagnostics and the direct potential field extrapolation. Conclusions. Spatial seismology inversion can be used as an effective method to independently measure various physical parameters, for example the density and magnetic field of coronal loops, which are consistent with the results obtained by DEM diagnostics and potential field extrapolation.

Natural electromagnetic oscillations in 4–12 Hz frequency range as measured by SWARM satellites and CARISMA magnetometer network

We examine magnetic field variations at 4–12 Hz frequencies in the upper ionosphere and on Earth. The ground response to the coherent oscillations at two SWARM satellites near and above the high frequency boundary of the nominal Pc1 range is studied. We use CARISMA data to analyze ground pulsations. Ionospheric oscillations are predominantly registered at geomagnetic latitudes above 65°, i. e. from the auroral zone to the polar cusp-cleft region. The oscillations at the same frequencies are recorded at auroral and subauroral ground stations at distances from 1500 to 3000 km from satellite footprint. Ratio RGI of the oscillation amplitude on Earth to that in the ionosphere retrieved from the observed data is compared to the values calculated for a finite radius Alfvén beam incident onto a quasi-real ionosphere. [Fedorov et al., 2018]. Radial distribution of RGI depends on the oscillation frequency and the altitude distribution of ionospheric parameters controlled mostly by season and local time. The most probable values of RGI range from 10–3 to 10–1. The RGI values obtained from the observed data agree with model ones at incident beam radius of about several hundred kilometers.

Improving the performance of room temperature magnetic regenerators using Al2O3-water nanofluid

The present study examines the use of Al2O3-water nanofluid as the heat transfer fluid in a magnetic regenerator and evaluates the improved cooling capabilities of the device. Room-temperature magnetic refrigeration exploits a special property of some materials, the “magnetocaloric effect”, that is the ability of the material to change its temperature when exposed to rapid changes in an external magnetic field. As adiabatic magnetic field variations of 1 to 1.5 T produce a small temperature change of a few degrees, active magnetic regeneration is often employed to achieve larger temperature spans for practical cooling applications. The effectiveness of this process greatly depends on the properties of the heat transfer fluid, which is usually a water-based mixture. High values of the fluid thermal conductivity enhance heat transfer allowing for higher cooling capacity. This work presents the outcome of a comprehensive simulation study evaluating the improved performance of a gadolinium-based regenerator using a water-based mixture with added Al2O3 nanoparticles as the heat transfer fluid. In this analysis, both the volume concentration of nanofluid and the particle size were varied. The combined effect of heat transfer enhancement and pressure drop increase was also investigated through the second law efficiency. On average, a more than 15 % increase in cooling capacity was observed when using Al2O3 (6 % vol, 20 nm particles), and the COP can be preserved or increased with a properly tuned regulation of the cycle time and the utilization factor of the regenerator.

Естественные электромагнитные колебания диапазона 4-12 Гц по наблюдениям на спутниках SWARM и сети магнитометров CARISMA

We examine magnetic field variations at 4–12 Hz frequencies in the upper ionosphere and on Earth. The ground response to the coherent oscillations at two SWARM satellites near and above the high frequency boundary of the nominal Pc1 range is studied. We use CARISMA data to analyze ground pulsations. Ionospheric oscillations are predominantly registered at geomagnetic latitudes above 65°, i. e. from the auroral zone to the polar cusp-cleft region. The oscillations at the same frequencies are recorded at auroral and subauroral ground stations at distances from 1500 to 3000 km from satellite footprint. Ratio RGI of the oscillation amplitude on Earth to that in the ionosphere retrieved from the observed data is compared to the values calculated for a finite radius Alfvén beam incident onto a quasi-real ionosphere. [Fedorov et al., 2018]. Radial distribution of RGI depends on the oscillation frequency and the altitude distribution of ionospheric parameters controlled mostly by season and local time. The most probable values of RGI range from 10–3 to 10–1. The RGI values obtained from the observed data agree with model ones at incident beam radius of about several hundred kilometers.

Archaeomagnetic analyses on fumiers burned under controlled experimental conditions

The improvement of the archaeomagnetic dating method requires compiling new and older data of the Earth's magnetic field (EMF) variations for the last millennia. Combustion events from fumier sequences have been proposed as good directional EMF recorders. However, they are subjected to diverse taphonomical processes and how these affect the archaeomagnetic record has not yet been studied. In order to evaluate it, here we report the first archaeomagnetic and rock-magnetic results on samples from experimentally recreated fumiers since 2014 under controlled conditions. A facies description with unprecedent resolution was used to study the variation of magnetic properties in depth. Rock-magnetic analyses indicate a homogenous magnetic mineralogy dominated by pseudo-single domain magnetite as main carrier in all facies, with not very high and similar contribution of the finest (superparamagnetic) grains. The low values of anisotropy of magnetic susceptibility (AMS) indicate that the studied sample set is mainly isotropic. The directional behaviour in well-preserved burned facies (here described as G, LM and DGB), are jointly characterized by highly reversible thermomagnetic curves, high Koenigberger (Qn) ratio values and intense, univectorial and normal polarity orthogonal NRM demagnetization diagrams. On the contrary, specimens affected by mechanical alteration processes are less magnetic and show anomalous directional behaviours. The high thermomagnetic reversibility of ashes indicates that they reached ca. 600–700 °C, in line with the thermocouples’ data. Temperatures of 460 °C were obtained for the DGB facies (subyacent black carbonaceous facies). Sampling of ashes located on the top of these combustion events should be avoided for archaeomagnetism. Being just beneath the last stabling episode they are the most prone to undergo mechanical alterations and do not preserve well the Earth's magnetic field direction. Despite their unlithified nature and the multiple taphonomic processes that fumier sequences may undergo, under certain quality criteria, they are valid geomagnetic field recorders providing both information of archaeological and geophysical interest.

Role of structural, morphological, and electronic characteristics in investigating the low temperature transport and magnetic behavior of Sr doped Sm2NiMnO6

Oxide double perovskites of the form R2NiMnO6 (R= rare-earth) are known to possess the multifunctional behavior. Herein, we have induced structural and electronic modifications in Sm2NiMnO6 system by Sr doping to form Sm2−xSrxNiMnO6 (x = 0.0, 0.2, and 0.4) and accordingly investigated the structural, morphological, electronic, dielectric, magnetic and magnetoresistance properties. Sm2NiMnO6 has monoclinic structure with P21/n space group and doping with Sr does not change the phase of compound. Microstructure studies suggest a decrease in the grain size with increase in Sr doping while elemental overlay and analysis suggest the presence of known elements in uniformity. Chemical valency indicates the existence of mixed valence of Ni and Mn cations along with presence of oxygen vacancies in all the sample of Sm2−xSrxNiMnO6 (x = 0.0, 0.2, and 0.4). Frequency (200 Hz to 2 MHz) and low temperature (100–320 K) dependence of dielectric measurements have been carried out to observe the behavior of dielectric constant and dielectric loss. With increase in concentration of Sr, the dielectric constant decreases while the dielectric loss increases. Temperature variation of ac conductivity as well as resistivity suggests the negative temperature coefficient of resistance, depicting the semiconducting behavior of all the samples. Temperature variation of magnetization in terms of field cooled (FC) and zero field cooled (ZFC) curves shows the presence of two magnetic transitions in all the three samples. One pertains to paramagnetic to ferromagnetic transition temperature and another is due to downturn in magnetization at lower temperature. Sr doping also causes an increase in the magnetic ordering temperature. Field variation of magnetization shows the ferromagnetic nature of all the three samples, where the saturation magnetization decreases with increase in temperature as well as increase in Sr concentration. Temperature dependence of resistivity at different magnetic fields indicates the presence of magnetoresistance effect in all the three samples. These studies highlight the role of Sr doping in determining and influencing the various physical properties discussed in this paper and the importance of these double perovskite systems for future material design and various technological applications.

An approach for computational blood flow under the joint effects of the electro-osmotic, magnetic field, chemical reaction and porosity

PurposeThe purpose of this study is to analyze the two-dimensional blood flow in the artery slant from the axis at an angle with mild stenosis under the joint effects of the electro-osmotic, magnetic field, chemical reaction and porosity using a new analytical method. In addition, the mathematical model presented by the researchers Tripathi and Sharma (2018c) was successfully developed by adding the effect of electro-osmosis and studying the impact of the new addition in the developed model on blood flow.Design/methodology/approachA new analytical method was used to find the analytical approximate solutions of two-dimensional blood flow in artery slant from the axis at an angle with mild stenosis. This technique is based on integrating the Akbari-Ganji and the homotopy perturbation methods.FindingsThe results of axial velocity, concentration, temperature and the wall shear stress for blood flow were analyzed in the cases of the absence and presence of electro-osmosis. Furthermore, in these two states of electro-osmosis, a contour plot was created to show the difference in the profile of velocity to the flow of blood when the magnetic field was increased and the altitude of stenosis was increased. The results showed that the new technique is effective and has high accuracy to determine the analytical approximate solutions of two-dimensional blood flow in artery slant from the axis at an angle with mild stenosis. The validity, utility and necessity of the new method were illustrated from the graphs of the new solutions; in addition, there is an excellent agreement with the results of previous studies.Originality/valueThis paper focuses on developing the mathematical model which was presented by the researchers Tripathi and Sharma (2018c), by adding the effect of the electro-osmosis to it, which has been successfully developed. According to the authors’ modest information, the new system has not been studied before. This current problem is solved by using an innovative approach known as the Akbari-Ganji homotopy perturbation method (AGHPM) which has not been used before in two cases: the presence and absence of the effect of electro-osmosis. This new technique afford new with effective and has high accuracy results. Furthermore, the new study (i.e. adding effect of electro-osmosis) with the applications of (variable viscosity, magnetic field, chemical reaction and porosity) illustrated the importance of applying electro-osmosis and how doctors can benefit from it during surgeries through proper use.

GPU propagation and visualisation of particle collisions with accurate model of ALICE detector magnetic field

The ALICE Collaboration at CERN developed a 3D visualisation tool capable of displaying a representation of collected collision data (particle trajectories, clusters and calorimeter towers) called the Event Display. The Event Display is constantly running in the ALICE Run Control Center as part of the Quality Assurance system, providing the monitoring personnel with visual cues about possible problems of both hardware and software components during periods of data gathering. In the software, particle trajectories (which are curved due to the presence of a magnetic field inside the detector) are generated from the physical parameters of detected particles, such as electrical charge and momentum. Previously this process in the Event Display used a uniform, constant magnetic field for these calculations, which differs from the spatial variations of the real magnetic field and does not model one of the two magnets used in the detector. Recently, a detailed model of the ALICE magnetic field was made available as a shader program for execution on the GPU. In this work we attempt to implement the reconstruction algorithm in a shader form as well, allowing us to combine it with the detailed model to create a full solution for rendering trajectories from collision event data directly on the GPU. This approach has several possible advantages, such as better performance and the ability to alter the magnetic field properties in real time. This was not previously done for ALICE and as such could be used in the future to upgrade the Event Display.

Temperature‐dependent electrical conductivity impact on radiative and dissipative peristaltic transport of boron nitride‐ethylene glycol nanofluid through asymmetric channels

AbstractMathematical simulation of biological fluids is of upmost significance due to its numerous medical uses. Interpreting various biological flows necessitates a thorough knowledge of the peristaltic mechanism. This paper presents a computational study for the peristaltic pumping within vertical asymmetric channels filled with BN‐EG nanofluid under the influence of temperature‐dependent electrical conductivity and thermal radiation. Experimental study showed that the nanofluid created by suspending Boron Nitride particles in a combination of Ethylene Glycol exhibited non‐Newtonian characteristics. Further, the Carreau's fluid model provides accurate predictions about the rheological properties of BN‐EG nanofluid. Various configurations of the outer boundaries are considered, namely, square wave, multi‐sinusoidal wave, trapezoidal wave, and triangular wave. A uniform magnetic field together with nanoparticles and mass concentrations, joule heating, first‐order chemical reaction as well as viscous dissipation are considered. Influences of the Dufour and Soret numbers are examined, and the cases of biological scientific assumptions which is known as low Reynolds number and long wavelength are applied. All the computations are obtained numerically using Mathematica symbolical software (ND‐Solve), and the obtained results are presented in terms of the axial velocity u, heat transfer rate Z, concentration profile Ω, temperature profile θ, extra stress tensor , pressure gradient , pressure rise and stream function ψ. The major outcomes revealed that the maximizing in electrical conductivity coefficient, variable viscosity coefficient and magnetic field parameter is better to obtain a higher rate of the heat transfer while the increase in thermo‐diffusion effects as well as linear thermal radiation coefficient causes a reduction in the rate of heat transfer.

Unsteady magnetized flow of micropolar fluid with prescribed thermal conditions subject to different geometries

Due to realistic implementations of heat transfer flows, this study communicates with the two cases of the prescribed thermal process. A comparative analysis of the time-dependent flow of a micropolar fluid between two problems of linear stretching sheet and exponential stretching sheet is demonstrated. In the context of the linear stretching sheet, the investigation covers situations involving prescribed surface temperature (PST) and prescribed heat flux (PHF). Likewise, for the exponential stretching sheet, the study examines cases of prescribed exponential order temperature (PEST) and prescribed exponential order heat flux (PEHF). For both problems, the two cases of the thermal process are examined for heat transfer analysis considering joule heating and nonlinear thermal radiation. The two-dimensional flow in the presence of a variable magnetic field is explored for both the linear and exponential stretching sheet problems. Graphical representations are employed to provide a comparative illustration of flow properties concerning relevant parameters for both cases. From the graphical and tabular analysis, we deduce that an exponential stretching sheet provides more consequential results as compared to a linear stretching sheet. Furthermore, the material parameter demonstrates an increase in the velocity field for both of the considered sheets.

Structure and magnetic properties of Gd2O3 nanoparticles obtained by the spark discharge method

Gadolinium oxide nanoparticles were obtained by the spark discharge electrophysical method. Structure, magnetic and magnetocaloric properties of Gd2O3 nanoparticles are comparatively analyzed. According to X-ray phase analysis, the synthesized Gd2O3 nanoparticles contain two crystallographic phases: cubic and monoclinic. The change in the magnetic part of the entropy dSM was determined from the measurement data of magnetic isotherms based on the Maxwell relation. The maximum value of dSM for a magnetic field variation amplitude of 2 T was approximately 17 J/kgK and was observed at a temperature of 2.5 K.

Momentum, heat and mass transfer in the hydrodynamic electrically conducting fluid flow over a stretching sheet

This study looks at the numerical results of magnetohydrodynamic liquid flowing across a stretching sheet at its stagnation point while also experiencing chemical reaction, viscous dissipation, thermal radiation and variable magnetic field. The fundamental partial differential equations that regulate physical phenomena are converted into nonlinear ordinary differential equations by using the appropriate similarity transformations. Later, resolved by numerically using Mathematica. The effects of various non-dimensional parameters like velocity ratio parameter ([Formula: see text]), porosity (k), magnetic parameter (M), radiation parameter (R), chemical reaction parameter ([Formula: see text]), etc. on the velocity, temperature and concentration profiles as well as on the local skin-friction and the local Nusselt number are discussed in detail and displayed through graphs. The numerical evaluation of the physical quantities was provided in tabular form for the various values of the relevant stream parameters. It is important to note that magnetic field interaction increases concentration distribution and fluid temperature while decreasing velocities at all domain flow locations.

Climatology of quiet time geomagnetic field variations at two locations in Antarctica

During geomagnetic quiet conditions, Indian Antarctic stations are considered to be located outside the auroral oval: Maitri (CGM coordinates: 63.3°S, 54.2°E) is equatorward and Bharati (CGM coordinates: 74.8°S, 98.4°E) is poleward of the auroral oval. Simultaneous observations of magnetic field variations at these two locations for 10-years (2013–2022) provide an opportunity to study quiet-time magnetic field patterns, if any. Geomagnetic quiet days with ΣKp ≤ 3 are selected, during which the lower values of solar wind and interplanetary parameters are also confirmed. Maitri station exhibits clear southern hemispheric solar quiet (Sq) type of magnetic field variation on geomagnetic quiet days in all seasons, indicating the influence of ionospheric dynamo due to thermospheric winds. Interestingly, Bharati station also displays regular and systematic magnetic field variations in all three components. The D-component at Bharati exhibits very strong variation at early morning hours (7–8 MLT), which is ∼2–4 times stronger than that of H-component, driving strong equatorward/northward currents during all seasons. Both stations show annual type of seasonal variation with peak amplitude during summer and least during winter. The schematic illustration of global and polar Sqs proposed here explains the results obtained through 10-years’ statistical study.

Numerical simulation of ultrashort-pulse reflectometry (USPR) on EAST

The microwave reflectometer is a popular non-intrusive plasma density diagnostic instrument on tokamaks that provides centimeter and millisecond level resolution. The ultrashort-pulse reflectometer (USPR) achieves plasma density measurement by emitting a chirped wave containing a broadband signal and measuring the time of flight from different frequency components. A USPR system is currently being built on EAST (Experimental Advanced Superconducting Tokamak) to meet the needs of diagnostic of the pedestal density evolution, such as high-frequency small edge-localized modes. In order to predict the density reconstruction of the EAST USPR system, this work presents a numerical simulation study of the beam propagation of the chirped wave of extraordinary waves (X-mode) in the plasma based on Python. The electron density profile has been successfully reconstructed by the reflection signal interpretation. The small gap between the right-hand cut-off layer and the electron cyclotron resonance layer, due to the low plasma density on the plasma edge, causes unexpected leakage from the transmitting microwave beam to the pedestal and the core region. This kind of ‘tunneling’ effect will cause the reflected signal to have energy loss in the low-frequency band. The study also discusses the influence of the poloidal magnetic field on the reflected signal. The spatial variation of the poloidal magnetic field will lead to the conversion between extraordinary (X) waves and ordinary (O) waves, which leads to energy loss in the reflected signals. The simulation results show that the ‘tunneling’ effect and the O-X mode conversion effect have little effect on the EAST USPR system. Therefore, the currently designed transmit power meets the working requirements.

Adoption of new strategy for molecularly imprinted polymer based in-tube solid phase microextraction to improve specific recognition performance and extraction efficiency

In-tube solid phase microextraction (IT-SPME) utilizing molecularly imprinted polymers (MIPs) as extraction phase has received wide attention due to various merits. However, low extraction efficiency and unsatisfactory recognition performance have limited its extensive application. To circumvent the limitations, a new strategy that implementation of magnetic fields during extraction stage was introduced to improve the extraction efficiency and recognition performance of MIPs-based IT-SPME. Firstly, using 2,4-dinitroaniline (2,4-DNA) as model template, a MIP mingled with magnetic nanoparticles (Fe3O4) was in-situ prepared in a capillary and employed as the microextraction column of IT-SPME. In the second step, a magnetic coil was wrapped the as-prepared MIP-based microextraction column so as to produce variable magnetic fields in extraction step. Results revealed that the application of magnetic field during the adsorption step improved the specific extraction performance towards template. The extraction efficiency and imprinting factor towards 2,4-DNA increased from 58% and 2.5 to 81% and 3.1, respectively. Practicality of the introduced magnetism-assisted IT-SPME technique based on MIP was demonstrated by on-line hyphenating with HPLC/DAD to quantify trace 2,4-DNA in a variety of environmental waters. High sensitivity (limit of detection was 0.060 μg/L), good precision (RSDs were below 10%) and satisfactory recoveries (82.1–111%) were obtained. Furthermore, the possible selective extraction mechanism under magnetic fields was deduced.

High optical spin-filtering in antiferromagnetic stanene nanoribbons induced by band bending and uniaxial strain

Non-equilibrium spin-polarized transport properties of antiferromagnetic stanene nanoribbons are theoretically studied under the combining effect of a normal electric field and linearly polarized irradiation based on the tight-binding model at room temperature. Due to the existence of spin-orbit coupling in stanene lattice, applying normal electric field leads to splitting of band degeneracy of spin-resolved energy levels in conduction and valence bands. Furthermore, unequivalent absorption of the polarized photons at two valleys which is attributed to an antiferromagnetic exchange field results in unequal spin-polarized photocurrent for spin-up and spin-down components. Interestingly, in the presence of band bending which has been induced by edge potentials, an allowable quantum efficiency occurs over a wider wavelength region of the incident light. It is especially important that the variation of an exchange magnetic field generates spin semi-conducting behavior in the bended band structure. Moreover, it is shown that optical spin-filtering effect is obtained under the simultaneous effect of uniaxial strain and narrow edge potential.

Convective heat transfer enhancement and entropy generation analysis for radiative flow of ferrofluid inside the enclosure with non-uniform magnetic field

The present work consists of investigating the thermal performance and entropy generation for the non-isothermal radiative-convective flow of magnetic-ferrofluid inside the cavity exposed to the variable magnetic field. The effects of Lorentz and Kelvin forces for magnetized liquid are associated with magnetohydrodynamic (MHD) and ferrohydrodynamic (FHD) are examined during this study. The penalty method is used to eliminate pressure terms from governing nonlinear system of partial differential equations, and then Galerkin finite element is utilized to reduce the system into a system of algebraic equations, which is then solved with the help of Newton Raphson method to obtain the required (unique) solution. The obtained results show that the thermal mixing and entropy generation increases with an increase in the magnetic number Mnf. The concentration of ferroparticles volume fraction (ϕ) from 0 to 0.05 increases the heat transfer rate by 62.78% and decreases the total entropy generation by 57.3%. The maximum 93.62% augmentation in the heat exchange rate is obtained at ϕ=0.05 and Mnf=103. The results of the present work can be used in obtaining geometric parameters and optimizing designs for effective energy transfer in chemical reactors, solar collectors, nuclear magnetic resonance imaging, heat exchangers, and dye removal from textile wastewater.

Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni95Cr5 layers

Understanding of the coexistence of normal and inverse magnetocaloric effects (MCE) makes it promising for use in magnetic cooling applications. This study discusses the selection of Ni95Cr5 layers and their expected magnetocaloric effects for an extended temperature range (200–800 K). These layers offer a wide range of suitable magnetic ordering temperatures as a function of thicknesses. A modified phenomenological model was used to estimate the entropy changes () and relative cooling power (RCP). Under adiabatic magnetic field variation, normal and inverse MCE are computed near the ferromagnetic-paramagnetic transition temperatures, T C and spin−glass transition temperatures, T G , respectively. Based on their values (= −0.06 to 0.11 J kg−1-K−1) and RCP( = 7.6 to 15.5 J kg−1) at the smallest magnetic field of 0.5 kOe, which are comparable to other MCE layer materials. We provide evidence of a strong correlation between the change in magnetic anisotropy (measured in terms of MR/MS and HC) below T G , which subsequently leads to the reversal of However, after annealing these effects somewhat vanish. The current study demonstrates that adjusting thickness, in addition to Cr doping, can externally regulate soft magnetic and magnetocaloric properties to create diverse magnetic ground states for future MCE and inverse MCE functionalities.

A numerical study of the nanofluid mixtures inside a Buoyancy-driven cavity in the presence of a variable magnetic field

While magnetic flow applications have become a topic of great interest for decades, the coupling between fluid flow and electromagnetic forces is not straightforward. Therefore, the necessity of a robust guideline to simulate these types of problems has become apparent. Moreover, the heat transfer capabilities and the interaction between electromagnetic forces such as Lorentz and Kelvin require further investigation.In this regard, two objectives are pursued to address the noted issues. First, a robust and flexible solution framework using User-Defined-Functions (UDF)s is presented so that magnetic flow applications can be investigated without software limitations such as discretization scheme, solution setup, and simultaneous use of other advanced modules. Next, the impact of electromagnetic forces on streamlines and isotherms has been studied, and the forces’ area of influence is carefully investigated.Based on the results, the introduced framework has successfully predicted consistent results for three previous studies. Next, by considering a wide range of Rayleigh (Ra), Hartmann (Ha), and Magnetic (Mn) numbers, valuable revelations regarding the force interactions, thermofluidic properties, and force area of influence were revealed. Finally, the situations in which the Kelvin and Lorentz forces are influential are identified based on dimensional analysis.

Radio Frequency-Based Diagnostics for Superconducting Magnets

Operation of high-field superconducting magnets relies on diagnostic instrumentation for measuring strain, temperature, and magnetic field variations, detecting quenching, and identifying performance problems. Discrete sensor implementation is costly, requires multi-channel data acquisition systems, and sensor density is often insufficient to resolve problematic locations spatially. Distributed sensing is a viable alternative approach providing location-specific diagnostic information over single terminal output. In particular, it can be the key to quench protection of high-temperature superconductor (HTS)-based magnets where hot spots are known to form and persist before a quench. Fiber-optic technology offers distributed sensing solution for magnets but suffers from drawbacks such as fiber fragility, high costs of optical interrogators, and difficulty in differentiating between physical quantities such as temperature and strain. We propose an alternative, robust, and easily integrable way of implementing distributed sensing in magnets using radio-frequency (RF) technologies. RF Time Domain Reflectometry (TDR) technique has been around for nearly 60 years, and it is an essential diagnostic tool used in multiple areas of technology and applied research. We discuss operational principles and practical implementation of RF TDR sensors capable of detecting local variations of strain, temperature, and magnetic field through changes in RF impedance and wave propagation time. Results of cryogenic testing of our TDR sensors with HTS tape conductors are presented. The perspective of enabling a new diagnostics paradigm for high-energy physics and fusion energy applications based on distributed RF sensing is discussed.