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China's aeromagnetic three-component detection system was successfully developed in 2017, but how to use the three-component data of a large area aeromagnetic field to conduct geological interpretation research is still in the initial stage. This study proposes that the vector map of the total intensity of magnetic anomaly drawn after the aeromagnetic three-component data was significantly facilitated in geological interpretation. The related literature and books have developed the reduction-to-the-pole formula for aeromagnetic three-component data, but it is not final. Therefore, this paper derives the ultimate simple reduction-to-the-pole method based on aeromagnetic three-component data for the first time using a deep theoretical formula. The simple model of a single anomalous body and the complex model of four anomalous bodies are designed. The aeromagnetic three-component data in different latitudes is used to analyze the effect of the aeromagnetic three-component data. The results show that the effect of aeromagnetic three-component data at low latitude is not ideal, and the vector arrowhead of the total intensity of magnetic anomaly drawn after the reduction-to-the-pole method for the aeromagnetic three-component data is studied. The total intensity vector arrowhead of the magnetic anomaly's total strength drawn after the three-component data of the magnetic field can point to the magnetic geological body, and the converged vector arrow's position can reflect the geological body's buried depth. Then, the idea is applied to the aeromagnetic three-component data in the northern part of China, and the vector arrowhead of the total intensity of the magnetic anomaly is drawn. The vector arrowhead diagram of the total intensity of the magnetic anomaly is upward and downward. This study proposes that the different orientation phenomenon of the arrowhead is due to the remanence in the region's magnetic geological body and is verified by comparing the geological data. [ABSTRACT FROM AUTHOR]

Compared with wet magnetic separation, dry magnetic separation has the advantages of saving water resources, short beneficiation process, less equipment investment, less floor space and low beneficiation cost. The grade of iron ore resources in China is getting lower and lower, and the dispersed grain size is line, so it is urgent to develop dry magnetic separator for line-grained materials. According to the structure and working principle of various types of dry magnetic separators, they are divided into several types, such as magnetic-gravity combined dry magnetic separator, direct feeding wind-gravity- magnetic combined dry magnetic separator, wind feeding dry magnetic separator and so on. Magnetic gravity combined dry magnetic separators mainly include fixed magnetic system barrel dry magnetic separator, double roll high intensity dry magnetic separator, bet rotating magnetic field dry magnetic separator, double ring moving magnetic system dry magnetic separator, dry high intensity magnetic plate separator, dry screen high intensity magnetic separator, vibrating high gradient dry magnetic separator and other typical types. Dred feeding wind-gravity-magnetic combined dry separator mainly includes wind drum dry magnetic separator, wind feeding dry magnetic separator, cylinder fluidized dry magnetic separator, three-stage dry permanent magnet cylinder magnetic separator? wind-magnetic coupling dry magnetic separator? dry wind-magnetic separator? wind-gravity-magnetic combined force field magnetic separator and other typical types. Wind feeding dry magnetic separator mainly includes wind feeding plate magnetic separator? new dry wind-magnetic combined magnetic separator? dry wind permanent magnet concentrator? wind feeding dry permanent magnet magnetic separator and other types. The structure? magnetic separation principle? characteristics and application scope of more than 20 kinds of dry magnetic separators are introduced? and the advantages and disadvantages of various dry magnetic separators are analyzed. [ABSTRACT FROM AUTHOR]

This study creates a three-dimensional surface spline (3DSS) model of mainland China based on surface and CHAMP satellite observations. Through this model, the magnetic field analyses of domestic plateau (Qinghai-Tibet Plateau 28°N–38°N, 78°E–102°E), plain (middle and lower reaches of Yangtze River Plain 27°N–34°N, 111°E–122°E), and marine (parts of the East and South China Seas 16°N–30°N, 123°E–136°E) areas have been investigated. Single models of plateau and plain have also been created. To compare and verify results, the corresponding two-dimensional (2DTY) and three-dimensional (3DTY) Taylor polynomial models have been derived. Issues such as the removal of disturbing geomagnetic fields, the data gap between surface and satellite level, and boundary effect are all seriously considered. With an aim to evaluate the resulting model, some randomly selected points are not join the modeling, by which we thereby inspected the results in terms of residuals, change rate absolutes, and Root Mean Square Error (RMSE). Results show that except component Y, the change rate absolutes of other components are less than 1% both in domestic and single models, which means that the modeling result of 3DSS is better than the other two models. Plateau and plain 3DSS models reflect the fine distribution of the magnetic field after comparison with domestic distribution. The 3DSS model fits the plateau best, followed by the plain, while the worst fit is in the marine area. This means that the modeling precision depends mainly on the number and distribution of measuring points. [ABSTRACT FROM AUTHOR]

A superconducting magnet with a warm-bore size of 800 mm and a center magnetic field of 9.4 T for the whole-body magnetic resonance imaging (MRI) system was developed in IEECAS, China. To achieve a highly homogeneous magnetic field over the 400 mm diameter of spherical volume (DSV), both active shimming and passive shimming techniques were employed. This paper mainly focuses on the implementation of passive shimming for the 9.4 T MRI magnet system. After four iterations, we were able to achieve peak-to-peak and root mean square field homogeneities over the DSV at 3.05 and 0.94 ppm, respectively. In addition, this paper analyzes the electromagnetic forces and system errors of passive shimming for ultra-high fields, providing valuable insights into MRI magnet engineering. [ABSTRACT FROM AUTHOR]

We investigate using satellite geomagnetic data and their derived field models to study the crustal field. We focus on China to understand whether field models completely explain the crustal field of the regional extent and whether a high-quality satellite contains additional information, particularly on small scales, enhancing crustal field studies and improving model resolution. We use Swarm satellite data and the CHAOS-6 model and examine along-track one-degree differences in latitude bin averages of satellite data to seek additional small-scale structures. The results show that the CHAOS-6 model does a very good job of explaining the data. The mean square deviation is ∼3 nT. Moreover, the model broadly explains secular variation with certain misfits but not consistent between tracks. We report an anomalous unmodeled feature in the data. However, as this is located close to the magnetic equator, this may be attributed to an external field source. We conclude that crustal field studies should primarily focus on models and not data. [ABSTRACT FROM AUTHOR]

South China belongs to the northern geographic branch of the Australasian strewn field (AASF) of tektites and microtektites, and this area is assumed to be part of the uprange region of the putative impactor trajectory that formed the yet undiscovered source crater. Ferromagnetic minerals in impact glass may record the magnetization process and thermal history of impact melt, but the possible identity of ferromagnetic minerals in AASF tektites from South China is elusive. Here, we perform a rock magnetism and crystallography study of iron‐sulfur spherules in Muong Nong‐type tektites from South China, revealing abundant single‐domain and pseudo single‐domain nano‐grains of magnetite within the spherules. This result is consistent with the detection of magnetic signals caused by single‐domain and pseudo single‐domain magnetite in these samples. Compared to the large value ranges of magnetic properties of tektites in the entire strewn field, individual specimens of both Muong Nong‐type and single splash‐form tektites have relatively homogeneous magnetic properties in terms of magnetic susceptibility, natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM) and NRM/SIRM ratio. The results indicate that the impact melt that formed each tektite specimen experienced similar thermal history, and most AASF tektites from South China were cooled in an ambient magnetic field that is the same order of magnitude as the Earth's magnetic field. Plain Language Summary: The vast Australasian strewn field (AASF) of tektites and microtektites was formed at 0.788 million years ago by an enormous impact that may have occurred somewhere in the Indochina Peninsula. The magnetic properties of tektites may record the cooling history and post‐ejection magnetization process of the tektite‐forming melt, which could provide additional insights into the possible impact location. AASF tektites from South China are a unique portion of this strewn field regarding the hypothesized impactor trajectory, and our earlier rock magnetism study suggested that tektites in this region exhibit systematically different magnetic properties. This work performs detailed geochemical and crystallographic analyses for iron‐sulfur spherules in Muong Nong‐type tektites from South China, revealing abundant nano‐sized magnetite grains in the interior that are consistent with being single‐domain and pseudo single‐domain magnetite. This result is consistent with the detection of magnetic signals caused by single‐domain and pseudo single‐domain magnetite in these samples. Most tektites from South China have relatively homogeneous magnetic properties in the interior. Their paleointensity has the same order of magnitude compared to the Earth's magnetic field. Key Points: Nano‐sized euhedral magnetite grains were discovered in Muong Nong‐type tektitesIndividual tektite specimens from South China usually exhibit relatively homogenous magnetic propertiesAustralasian tektites in South China have been magnetized in an Earth‐strength magnetic field [ABSTRACT FROM AUTHOR]

The CSES high precision magnetometer (HPM), consisting of two fluxgate magnetometers (FGM) and one coupled dark state magnetometer (CDSM), has worked successfully for more than 5 years providing continuous magnetic field measurements since the launch of the CSES in February 2018. After rechecking almost every year's data, it has become possible to make an improvement to the in-flight intrinsic calibration (to estimate offsets, scale values and non-orthogonality) and alignment (to estimate three Euler angles for the rotation between the orthogonalized sensor coordinates and the coordinate system of the star tracker) of the FGM. The following efforts have been made to achieve this goal: For the sensor calibration, FGM sensor temperature corrections on offsets and scale values have been taken into account to remove seasonal effects. Based on these results, Euler angles have been estimated along with global geomagnetic field modeling to improve the alignment of the FGM sensor. With this, a latitudinal effect in the east component of the originally calibrated data could be reduced. Furthermore, it has become possible to prolong the updating period of all calibration parameters from daily to 10 days, without the separation of dayside and nightside data. The new algorithms optimize routine HPM data processing efficiency and data quality. [ABSTRACT FROM AUTHOR]

The small data global well-posedness of the 3D incompressible Navier--Stokes equations in R³ with only one-directional dissipation remains an outstanding open problem. The dissipation in just one direction, say, 2 1u is simply insufficient in controlling the nonlinearity in the whole space R³. The beautiful work of Paicu and Zhang [Sci. China Math., 62 (2019), pp. 1175-1204] solved the case when the spatial domain is bounded in the x1-direction by observing a crucial Poincaré-type inequality. Motivated by this Navier-Stokes open problem and by experimental observations on the stabilizing effects of background magnetic fields, this paper intends to understand the global well-posedness and stability of a special 3D magnetohydrodynamic (MHD) system near a background magnetic field. The spatial domain is R³, and the velocity in this MHD system obeys the 3D Navier-Stokes with only one-directional dissipation. With no Poincaré-type inequality, this problem appears to be impossible. By discovering the mathematical mechanism of the experimentally observed stabilizing effect and introducing several innovative techniques to deal with the derivative loss difficulties, we are able to bound the Navier-Stokes nonlinearity and solve the desired global well-posedness and stability problem. [ABSTRACT FROM AUTHOR]

To explore an efficient approach refining seismomagnetic information through magnetic field survey technology, the author introduces the seismomagnetic monitoring system of the capital region in China. It includes field measurement techniques, data processing methods and application performance. The variation characteristics of the crustal magnetic field and seismomagnetic information in this area are systematically calculated and statistically analyzed based on the geomagnetic data products of the X, Y, and Z components. The results show that the mean amplitudes of X, Y and Z of the crustal magnetic field in the study area are 1.87, 1.90, and 1.39 nT, and the mean square deviations are 2.41, 2.48, and 1.94 nT, respectively. The epicenters of future large earthquakes will mostly lie near the "0" value line of crustal magnetic field variation with very low amplitude, which X, Y and Z elements are 18.7, 45.5 and 53.9% of the mean values in the survey area, respectively, and rise obviously after the earthquake. There is a high correlation between the location of the epicenter and the anomalous region of low spatial variation ratio of geomagnetic field secular variation. [ABSTRACT FROM AUTHOR]

South China, the northern part of the Australasian strewn field (AASF) of tektites and microtektites is located at the uprange of the hypothesized source crater that is still unconfirmed. Magnetic properties of impact glasses are an important indicator of their source materials and thermal history. Extensive magnetic investigations have been performed on various AASF tektites sampled from both the Indochina Peninsula and further south, but such information remains sparse for those sampled from South China. Here, we present a detailed rock magnetism study for both Muong Nong‐type and splash‐form AASF tektites from South China, showing that all the tektites have rather weak remanent magnetization, but ferromagnetic information can be extracted from their dominating paramagnetic signal. Signals caused by superparamagnetic particles are elusive, but those of single domain magnetite are detected in the splash‐form tektites, and signals of pseudo‐single domain magnetite are discovered in the Muong Nong‐type tektites. Each morphological type of tektites from a same geographic area exhibits large dispersions in their magnetic properties. Across the entire AASF, the Muong Nong‐type tektites from South China exhibit the lowest average magnetic susceptibility, and the splash‐form tektites exhibit the smallest average natural remanent magnetization and ratio of equivalent magnetization. The observed heterogeneous magnetic properties are mainly caused by the different contents and sizes of magnetic particles, which can be explained by the different shock level and/or cooling history of the tektite melts. Micro‐sized immiscible Fe‐S spherules in the Muong Nong‐type tektites from South China were likely originated from the pre‐impact target. Plain Language Summary: About 0.78 million years ago, an about 1 km diameter asteroid or comet ended its trajectory on Earth. Instantaneously, massive continental sediments were molten and ejected, and natural glasses (tektites) were quenched and deposited across vast areas over 1 × 108 km2, forming the largest known Cenozoic strewn field of tektites and microtektites, the Australasian strewn field (AASF). The impact site is still unconfirmed. Magnetic properties of impact glasses are indicative to their source materials and thermal history. This study presents the first rock magnetic measurements for AASF tektites from South China. We find that while the samples are dominated by paramagnetic signals, signals caused by single domain magnetite are detected, and the Muong Nong‐type tektites contain pseudo‐single domain magnetite. Signals of superparamagnetic grains are elusive. With heterogeneous magnetic properties, tektites from South China generally exhibit lower magnetic susceptibility, natural remanent magnetization, and ratios of equivalent magnetization than the rest of AASF. The observed magnetic properties can be explained by different shock levels and cooling histories of the tektite melts, but strong magnetic field(s) recorded by some Muong Nong‐type tektites have an unknown origin. The first occurrence of Fe‐S spherules in tektites from South China might originate from target materials. Key Points: The first comprehensive rock magnetism study is performed for both splash‐form and Muong Nong‐type tektites from South ChinaSamples from China generally exhibit lower magnetic susceptibility, natural remanent magnetization, and ratio of equivalent magnetizationDifferent shock levels and cooling histories of tektite melt can explain the observed magnetic properties, and Fe‐S spherules are found [ABSTRACT FROM AUTHOR]

In well‐buffered modern soils, higher annual rainfall is associated with enhanced soil ferrimagnetic mineral content, especially of ultrafine particles that result in distinctive rock magnetic properties. Hence, paleosol magnetism has been widely used as a paleoprecipitation proxy. Identifying the dominant mechanism(s) of magnetic enhancement in a given sample is critical for reliable inference of paleoprecipitation. Here, we use high‐resolution magnetic field and electron microscopy to identify the grain‐scale setting and formation pathway of magnetic enhancement in two modern soils developed in higher (∼580 mm/y) and lower (∼190 mm/y) precipitation settings from the Qilianshan Range, China. We found that both soils contain 1–30 μm aeolian Fe‐oxide grains with indistinguishable rock magnetic properties, while the higher‐precipitation soil contains an additional population of ultrafine (<150 nm) magnetically distinct magnetite grains. We show that the in situ precipitation of these ultrafine particles, likely during wet‐dry cycling, is the only significant magnetic enhancement mechanism in this soil. These results demonstrate the potential of quantum diamond microscope magnetic microscopy to extract magnetic information from distinct, even intimately mixed, grain populations. This information can be used to evaluate the contribution of distinct enhancement mechanisms to the total magnetization. Plain Language Summary: Reconstructing how natural climate variations in the past influenced rainfall patterns is important for understanding how rainfall would respond to our current changing climate. The amount and properties of microscopic, magnetic minerals in soil can change due to variation in soil moisture; therefore, characterizing the magnetic properties of soils can aid in quantifying past rainfall. We use the quantum diamond microscope (QDM), a device that allows micrometer‐scale mapping of magnetic sources in rock and soil samples, to investigate the magnetic properties of two soils formed in low‐ and high‐rainfall environments. We find that, although both soils contain wind‐blown, magnetic dust, only the high‐rainfall soil contains an abundant, highly magnetic population of magnetite grains formed in soil pore spaces during repeated cycles of wetting and drying. These observations demonstrate the dominant pathway by which soil magnetism responds to rainfall and showcase the ability of QDM mapping to reliably identify the mechanism of magnetism modification in soils. Key Points: Both high and low precipitation soils contain aeolian grain population with indistinguishable magnetic propertiesHigh precipitation soil alone contains anhysteretic remanent magnetization‐susceptible, <150 nm magnetites inferred to be formed from wet‐dry cycling in pore spacesMagnetic field microscopy is able to quantify rock magnetic properties of intimately mixed grain populations and pinpoint their locations [ABSTRACT FROM AUTHOR]

In order to study in detail the characteristics of the lithospheric magnetic field and underground magnetic susceptibility structure in the East Dabie region of China, the magnetic data have been collected at 108 geomagnetic total intensity measuring points and 65 geomagnetic profile measuring points located in this region. Using a matching filter method and inverting the underground magnetic susceptibility of the medium, shallow and deep models of the lithospheric magnetic field, Curie-isothermal surface depth distribution and magnetic structure model of the underground medium have been obtained. The results show that the lithospheric magnetic field in the East Dabie region is distributed as a positive anomaly band or mass in the Jianghuai uplift, Tanlu fracture belt and the lower Yangtze uplift. In the North Huaiyang fold belt, it passes through with a huge negative anomaly in an E–W direction. Comparing the lithospheric magnetic field with the superficial magnetic field, strikes and cutting depths of several buried faults in this area can be found. The deep lithospheric magnetic field reflects the distribution and composition of the crustal basement in the region to a certain extent. The Curie-isothermal surface depth in the interior can be used to reveal the distribution of magmatic activity in the study area. Some deep and large faults have a certain controlling effect on the distribution of magnetic structures, and the epicenters of earthquakes in Dabie Mountain are concentrated in horizontally high magnetic structures. The above research is of great significance for studies of the lithospheric magnetic field and the relationship between underground magnetic structure and deep structure in the East Dabie region. [ABSTRACT FROM AUTHOR]

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Undulators are important devices for accelerator-based light sources whose magnetic field quality determines the photon beam performance. Superconducting-type undulators have been developing rapidly in recent years around the world. The insertion device group at the Institute of High Energy Physics (IHEP) in China started an R&D project to develop prototypes of superconducting undulators (SCUs). A half-meter-long planar SCU has been produced recently. The SCU was designed based on the simulation program OPERA-3D giving a period length of 15 mm and a gap of 7 mm. This prototype was manufactured and fabricated precisely, and was then tested by vertically submerging in liquid helium in a Dewar. After quench training several times, the maximum current in the main coils reached 480 A. The magnetic field was measured by Hall probes mounted on a sledge in the middle of the undulator gap. The peak magnetic field reached 1 T. The measurement results indicate that correction coils with suitable current can not only optimize the magnetic first and second integrals but also reduce the phase error, which is expected by design. [ABSTRACT FROM AUTHOR]

In aeromagnetic measurement, accurate compensation for the interference magnetic field generated by the aircraft platform due to the aircraft maneuvering in the Earth's magnetic field is an important prerequisite for the accurate identification of the magnetic anomaly signal of the detection target. The flaws of the traditional calibration flight scheme in aeromagnetic interference compensation are firstly analyzed, and then an improved scheme is proposed, featuring smaller calibration flight areas, more simplified maneuvers, shorter flight route and less influence from the magnetometer's direction and extreme weather. The improved scheme can enhance the robustness of the aeromagnetic interference compensation matrix and improve the compensation efficiency, and thus both the solved magnetic compensation coefficients and compensation effects are significantly improved. The experimental results of the aeromagnetic interference compensation in an area of Inner Mongolia of China show that the average accuracy of the repeated survey lines, which are compensated by the improved scheme, can be increased by 5 and 3 nT, respectively, compared with the uncompensated results and the results compensated by the traditional scheme. Therefore, the effectiveness and superiority of the improved calibration flight scheme is fully proved. Plain Language Summary: Aeromagnetic measurement technology is the most economical and effective technical means to obtain high‐precision and high‐resolution geomagnetic information. Because the aircraft used in aeromagnetic measurement is composed of ferromagnetic materials, it will produce an interference magnetic field when maneuvering in the Earth's magnetic field. In order to obtain pure geomagnetic field measurement data, it is necessary to compensate the interference magnetic field. The traditional calibration flight scheme is widely used in the aeromagnetic interference compensation, and has played an important role in the existing aeromagnetic measurement. However, with the continuous improvement of the measurement accuracy of airborne magnetometers, there are higher requirements for calibration, and some defects of the traditional calibration flight scheme are found in practice. Hence, an improved calibration flight scheme is proposed in this paper, which features smaller calibration area, shorter flight route, simplified maneuvers and less influence from the direction of the magnetometer. The experimental results show that the modified scheme can improve the average accuracy of repeated survey lines by 3 nT compared with the traditional one. Therefore, the improved scheme can be directly applied in the aeromagnetic interference compensation of scalar, vector and gradient magnetic measurement of manned and unmanned aerial vehicle (UAV). Key Points: An improved calibration flight scheme is proposed in the aeromagnetic interference compensationEffectiveness and superiority of the improved calibration flight scheme are validated by actual flight dataCompared with the traditional scheme, the improved one can increase the average accuracy of repeated lines by 3 nT [ABSTRACT FROM AUTHOR]

The High Energy Photo Source (HEPS) is being built in China and the magnets are in batch production. The octupole magnets with skew quadrupole component used in the storage ring have been designed and manufactured. The octupole has an aperture of 30 mm, a field gradient of 735000 T/m3 and a length of 0.26 m. In this paper, detailed magnetic design of HEPS octupole magnets is presented. Different design schemes of the skew quadrupole coils are compared, and the temperature effect on magnetic center and the integral field in the first batch of octupole magnets are also given. In addition, the influence of the combined power-on mode on the magnetic field is studied. [ABSTRACT FROM AUTHOR]

Controlled source audio magnetotelluric (CSAMT) has good depth penetration and high data quality. However, the Cagniard apparent resistivity calculated in the near- field zone and transition zone is distorted, and collecting electric field components in some specific landscapes requires a high cost, such as desert, permafrost, and water areas. The magnetic field y-component (Hy) is not restricted by bad electrode grounding conditions, and the signal level is greater than that of the magnetic field z-component (Hz), which can be used to obtain the ground resistivity. A simple algorithm was used to calculate the apparent resistivity defined by Hy, and the response characteristics and measurement range were analysed by model calculation. The results show that the Hy full-field apparent resistivity has no obvious distortion. This method is applied to geological surveys in the Xiong'an New Area, China. The results indicate that the detection depth of the Hy full-field apparent resistivity is better than that of electric field x-component (Ex), and the signal-to-noise ratio is better than that of Hz. Moreover, the 1D and 2D inversion results are in good agreement with the known geological conditions. This method can extend the observational conditions and range of CSAMT. [ABSTRACT FROM AUTHOR]

Apparent resistivity is a significant tool in the controlled-source electromagnetic method (CSEM). The Cagniard apparent resistivity, which is defined by the ratio of the magnetic and electric fields, has been widely used in CSEM interpretation. However, it is only suitable for the far zone, where the signals are weak. Although another apparent resistivity based on horizontal electric field E x can work in transition zone, its measurable zone is narrow. To better take the advantage of strong signals in non-far zone, we present a novel apparent resistivity by sophisticatedly combining the horizontal electric field and vertical magnetic field. We analyze the asymptotic characteristic of our apparent resistivity in the near and far zones using a theoretical formula. Synthetic data from the layered model show that when in the far zone, our apparent resistivity obtains the same performance as the Cagniard resistivity and E x resistivity. Besides, our apparent resistivity can still wok well when azimuth approaches 45° in the tranzition zone. Field data collected in Tongling, China further demonstrate the practicability and advantages of our apparent resistivity. [ABSTRACT FROM AUTHOR]

Magnetic anomalies commonly contain anomalies generated by crustal rocks that have variable mineral compositions and natural remanent magnetizations. Recovery of magnetic parameters from superimposed magnetic anomaly sources is therefore important for mineral exploration and geological studies. Superposition of magnetic anomalies leads to nonnegligible errors of inversion and interpretation. Therefore, extraction of magnetic anomalies is essential for magnetic data processing; however, existing methods cannot extract magnetic anomalies caused by sources without substantial depth differences. A novel low‐rank method is proposed for extracting a target magnetic anomaly from a superimposed anomaly. The low‐rank feature of the magnetic anomaly is used to obtain the target anomaly by reducing the Schatten‐p norm of the superimposed anomaly according to the possible target source distribution. The target magnetic anomaly can then be extracted from the data generated by the source interference at the same or different depths. The accuracy of the proposed method was verified using synthetic modeling. Magnetization vector information for individual igneous rocks was recovered from extracted magnetic anomalies via 3‐D inversion of field data from Yeshan (eastern China) that contain complex magnetic anomaly superpositions. The distributions and lithologies of five buried igneous rocks, including basalt, diabase, and granodiorite, were then identified. The proposed method expands the problem of separating magnetic information from rocks in different layers with large depth differences to rocks within the same or other layers and recovers geometric and physical information for each targeted magnetic source from the superimposed anomaly. Plain Language Summary: Magnetic rocks inherit different magnetic characteristics that depend on the type of rock and the features of the geomagnetic field present when the rock formed. Even for rocks at the same locality, the magnitude and direction of the magnetic vectors caused by the rocks are often different. Magnetic field observations contain mixed magnetic information from the geomagnetic core field and from all the rocks under and near the observation area, which causes serious problems for certain types of geological study. Therefore, we developed a new method to recover the magnetic anomaly caused by a target source from mixed magnetic information. We explain how the proposed method works and present a mathematical model. The robustness of the parameters of the proposed method is assessed using synthetic models. Synthetic experiments designed to test the accuracy of the proposed method indicated that the magnetic anomaly of the target rock could be recovered with high accuracy. Finally, we applied the proposed method to study field magnetic information in Yeshan, eastern China. Five magnetic anomalies caused by five isolated rocks were obtained using the proposed method, and the magnetic information, distributions, and lithologies of the five rocks were determined. Key Points: Magnetic data contain superimposed signals from multiple rocks that make extraction of magnetic anomalies for targeted sources challengingA novel low‐rank framework is proposed to extract target anomalies from superimposed magnetic anomaliesDetailed information derived from superimposed anomalies includes a magnetization vector model for each target source [ABSTRACT FROM AUTHOR]

Microchannel plate photomultiplier tubes (MCP-PMTs) with high temporal resolution and low dark count rates will be used as single-photon detectors for the Super Tau-Charm Facility (STCF) proposed in China. Similar to other RICH or DIRC detectors, MCP-PMTs in the STCF need to operate properly in an axial magnetic field of about 1.5 T. We study the magnetic field tolerance of MCP-PMTs with the simulation methods based on the Furman model as a secondary electron emission model and the particle-in-cell method for tracking electrons. The effects of MCP structural parameters (aperture $D$ , length-to-diameter ratio $L/D$ , bias angle $\theta $ , and applied voltage $U$) on the magnetic field tolerance are simulated. The results show that the smaller the $D$ and the smaller the $L/D$ of the MCP, the better its magnetic field tolerance. By increasing the MCP bias angle, its magnetic field tolerance increases first and then weakens. The applied voltage does not affect its magnetic field tolerance. Changing the angle between the magnetic field and the normal direction to the microchannel plate (MCP), the gain decays fastest when the magnetic field direction is parallel to the axial direction of the MCP channels; at a magnetic field direction of 60°, the MCP gain decays the slowest. For MCP-PMTs, the change in the magnetic field direction causes the alteration of the motion direction of the electron cloud in the gaps (cathode-MCP1, MCP1-MCP2, and MCP2-anode), which is the principal reason for the difference in its gain in different magnetic field directions with the same magnetic field strength. The magnetic field tolerance of different assembly methods of two MCPs (i.e., two, three, or four electrodes for applying high voltage) is simulated. The results show that two MCPs’ multiplication structure with the four-electrode assembly method is an appropriate choice. [ABSTRACT FROM AUTHOR]

Aiming at the complexity of end structures in the end region of large synchronous machines, it is difficult to obtain an analytical method for the end leakage magnetic field. In order to solve such a problem, a new analytical algorithm (NAA) considering the influence of the rotor end shaft and air gap is proposed. The mirror image of the rotor end current with the core end plane and the rotor shaft cylinder as mirror surfaces is studied. The air‐gap effect is considered by the equivalent air‐gap current, and the equivalent air‐gap current equation of synchronous machines in the polar coordinate system is derived. Then, a 300Mvar synchronous condenser (SC) is proposed for the first time in China as an example; according to the Biot–Savart law and the superposition principle, the end leakage magnetic field of the SC under no‐load condition is calculated, and the influence of different shaft structures on the end leakage magnetic field is analysed. Finally, the calculation results are compared with the 3‐D finite element method, which verifies the accuracy of the NAA. [ABSTRACT FROM AUTHOR]

This study utilizes the 62208000 Swarm satellite data to establish a high-precision main magnetic field at the height of the satellites in China and its adjacent regions. The CHAOS-6 model is used to remove the crustal and external fields and obtain 2788 main field grid data. We use the main field grid data to build a three-dimensional (3D) surface spline (3DSS) model of the satellite altitude in China. Other regional models (namely the 3D, two-dimensional (2D) Taylor, and 2D surface spline models) and the CHAOS-6 model are employed to model and analyze the same region. The results show that the 3DSS model can represent a good fitting for the northward (X) and eastward (Y) components and the total intensity (F). This model demonstrates the most stable results for the 20 points that did not take part in the modeling. Compared with the other three regional models, the root—mean—square error values and the average residuals of the new model are approximately 65% and 69% lower for each component, respectively. This study does not rely on ground station data to derive a more accurate regional main field model. The results further show that less data height difference and high-density data distributions greatly improve the regional model accuracy. The new model has a certain application value to related space geophysics, such as in spatial positioning and navigation, and to the study of regional magnetic anomalies. [ABSTRACT FROM AUTHOR]

The weak-field approximation, implying a linear relationship between Stokes- V / I and the longitudinal magnetic field [ B ∥ ], often suffers from saturation observed in strong magnetic-field regions such as sunspot umbrae. In this work, we seek to improve the magnetic-field observations carried out by the Solar Magnetic Field Telescope (SMFT) at the Huairou Solar Observing Station, China. We propose using a non-linear relationship between Stokes- V / I and B ∥ to derive the magnetic field. To determine the form of the relationship, we perform a cross-calibration of the observed SMFT data and magnetograms provided by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory. The algorithm for the magnetic-field derivation is described in detail. We show that using a non-linear relationship between Stokes- V / I and B ∥ allows us to eliminate magnetic-field saturation inside the sunspot umbra. The proposed technique enables one to enhance the reliability of the SMFT magnetic-field data obtained even long before the space-based instrumentation era, since 1987. [ABSTRACT FROM AUTHOR]

We construct an integrable quantum spin chain that includes the nearest-neighbor, next-nearest-neighbor, chiral three-spin couplings, Dzyloshinskyâ€"Moriya interactions and unparallel boundary magnetic fields. Although the interactions in bulk materials are isotropic, the spins nearby the boundary fields are polarized, which induce the anisotropic exchanging interactions of the first and last bonds. The U (1) symmetry of the system is broken because of the off-diagonal boundary reflections. Using the off-diagonal Bethe ansatz, we obtain an exact solution to the system. The inhomogeneous T â€" Q relation and Bethe ansatz equations are given explicitly. We also calculate the ground state energy. The method given in this paper provides a general way to construct new integrable models with certain interesting interactions. [ABSTRACT FROM AUTHOR]

We construct the grand partition function of the system of massive Dirac fermions in a uniform magnetic field from Landau levels, through which all thermodynamic quantities can be obtained. Making use of the Abelâ€"Plana formula, these thermodynamic quantities can be expanded as power series with respect to the dimensionless variable b = 2 eB / T 2. The zero-field magnetic susceptibility is expanded at zero mass, and the leading order term is logarithmic. We also calculate scalar, vector current, axial vector current and energy-momentum tensor of the system through ensemble average approach. Mass correction to chiral separation effect is discussed. For massless chiral fermions, our results recover the chiral magnetic effect for right- and left-handed fermions, as well as chiral separation effect. [ABSTRACT FROM AUTHOR]

The Tianwen-1 mission is China's first Mars exploration mission. To complete the scientific objectives of "orbiting, landing, and patrolling" in one mission, thirteen instruments for acquiring multi-disciplinary data are configured. The data products with rich ancillary data and flexible structures will facilitate the data application. To integrate the requirements of experts from disparate disciplines and leverage new information technologies, a complete redesign of data products is promoted in the Tianwen-1 mission. We discuss the whole process of data product generation from the data pipeline design to data validation. We design the various data products according to the application requirements of each data type, including radar echo data, spectrum data, image data, energy spectrum data, magnetic field data, meteorological data, and acoustic data. Since various error sources will exist in the generation chain of the data products, data validation is essential before release to the public; the validation activities are discussed at the end. We deliver these scientific products to the community in a timely manner, with ancillary information and quality information. This paper can provide practical reference for Tianwen-1 data application. [ABSTRACT FROM AUTHOR]

The Interaction between magnetohydrodynamic (MHD) instabilities and energetic-ions in in Tokamak plasmas is one of the key issues, which is crucial for the steady-state long pulse operation of future reactors.HL-2A is the first magnetic confined fusion experiment research tokamak device with the non- circular cross-section and advanced divertor configuration in China. Tearing mode is one kind of fundamental resistive MHD in stability that can change the topology of the magnetic field, induce a shortcut in transport and even trigger major disruptions. Energetic-ions are inevitably produced in burning plasmas and various external auxiliary heating processes. There are still some critical problems on debate, such as the resonance condition between tearing mode and energetic-ions, the mechanism of energetic-ions loss induced by this resonant interaction. So farthere is still not acomplete simulation work with respect to the resonant interaction between tearing mode and energetic-ions in the magnetically confined plasmas. Hence, this review paper focuses on the following three aspects. Firstly, we retrospect the history o f the interaction between tearing mode and energetic-ion s. Secondly, based on HL-2A experiments, the numerical simulation results with respect to the resonant interaction be tween energetic-ions and t earing modes and the loss mechanism of energetic-ions are introduced. Finally, the prospects of the resonant interaction between energetic-ions and t earing mode in future reactors are made. [ABSTRACT FROM AUTHOR]

The concept that geospace storms are comprised of synergistically coupled magnetic storms, ionospheric storms, atmospheric storms, and storms in the electric field originating in the magnetosphere, the ionosphere, and the atmosphere (i.e., electrical storms) was validated a few decades ago. Geospace storm studies require the employment of multiple-method approaches to the Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere–Earth system. This study provides general analysis of the 30 August–2 September 2019 geospace storm, the analysis of disturbances in the geomagnetic field and in the ionosphere, as well as the influence of the ionospheric storm on the characteristics of high frequency (HF) radio waves over the People's Republic of China. The main results of the study are as follows. The energy and power of the geospace storm have been estimated to be 1.5×1015 J and 1.5×1010 W, and thus, this storm is weak. The energy and power of the magnetic storm have been estimated to be 1.5×1015 J and 9×109 W, i.e., this storm is moderate, and a characteristic feature of this storm is the duration of the main phase of up to 2 d. The recovery phase also was lengthy and was no less than 2 d. On 31 August and 1 September 2019, the variations in the H and D components attained 60–70 nT, while the Z -component variations did not exceed 20 nT. On 31 August and 1 September 2019, the level of fluctuations in the geomagnetic field in the 100–1000 s period range increased from 0.2–0.3 to 2–4 nT, while the energy of the oscillations showed a maximum in the 300–400 to 700–900 s period range. During the geospace storm, a moderately to strongly negative ionospheric storm manifested itself by the reduction in the ionospheric F-region electron density by a factor of 1.4 to 2.4 times on 31 August and 1 September 2019, compared to the its values on the reference day. Appreciable disturbances were also observed to occur in the ionospheric E region and possibly in the Es layer. In the course of the ionospheric storm, the altitude of reflection of radio waves could sharply increase from ∼150 to ∼300 –310 km. The atmospheric gravity waves generated within the geospace storm modulated the ionospheric electron density; for the ∼30 min period oscillation, the amplitude of the electron density disturbances could attain ∼40 %, while it did not exceed 6 % for the ∼15 min period. At the same time, the height of reflection of the radio waves varied quasi-periodically with a 20–30 km amplitude. The results obtained have made a contribution to the understanding of the geospace storm physics, to developing theoretical and empirical models of geospace storms, to the acquisition of detailed understanding of the adverse effects that geospace storms have on radio wave propagation, and to applying that knowledge to effective forecasting of these adverse influences. [ABSTRACT FROM AUTHOR]

While the use of experiments is important for developing students' scientific knowledge and skills, challenges may arise when teachers and students are conducting experiments in class, such as non‐reusable experimental resources, safety issues and difficulties simulating some specific effects. Augmented reality (AR) technology affords an alternative approach to conducting experiments by bringing students a virtual–real mixed learning environment. In this study, taking junior high school physics knowledge on the magnetic field as an example, we designed and developed an AR‐based mobile simulated experiment tool. This study investigates the effect of the AR‐based experiment on students' knowledge improvement and cognitive load compared with 3D and traditional experiments. A sample of 122 ninth‐grade students was randomly chosen and assigned to three groups (AR, 3D and Traditional). The results demonstrate that students in the AR group performed better than those in the 3D and Traditional groups in terms of their knowledge improvement. The AR group students also experienced the lowest cognitive load among the three groups. Moreover, students had positive perceptions about AR and 3D tools. The implications of this study are discussed. Lay Description: What is already known about this topic: Experiment is an important method for students' magnetic field learning.Traditional magnetic experiment consists of various procedures that may cause some inconvenience during learning.Augmented reality (AR) provides a virtual–real fusion environment to assist teaching and learning.While some studies indicate positive impact of AR on learner's cognitive load, some do not. What this paper adds: An AR‐based mobile simulated experiment tool was proposed based on the junior high school physics knowledge, the magnetic field.A Comparison was made among AR, 3D and traditional experiment for magnetic field learning.Higher knowledge improvement and lower cognitive load were observed in the AR group.3D and Traditional groups showed similar knowledge improvement and cognitive load. Implications for practice and/or policy: The AR design with hand‐held devices has unlimited scalability of educational applications.Serving the real object as marker and using the professional algorithm to simulate some specific phenomenon were recommended in future AR studies.The findings indicated that AR experimental tool had a statistically significant effect on students' knowledge improvement and cognitive load.The similar result between 3D and Traditional groups implies that not everything virtualized is good; we must consider the actual teaching and learning situations. [ABSTRACT FROM AUTHOR]

We present new regional models, denoted CLAS, of the Chinese lithospheric field, combining the long-wavelength information provided by satellite-derived models: CHAOS-6, MF7, LCS-1 and NGDC720, and an extremely high-quality compilation of 97 994 aeromagnetic survey data with 10 km × 10 km resolution for shorter wavelength. The models are estimated using a depleted basis of global spherical harmonic functions centred on China. CLAS models are determined include harmonic degrees up to 400. Although some accuracy of aeromagnetic data is lost in order to balance the consistent of two data sets, the results show that CLAS models have a high correlation with the satellite models at low-degree terms (degree correlation > 0.9) but with more power at high-degree terms, reflecting more features of the lithospheric field in continental China. Examples of improvement include Changbai mountains, Sichuan Basin and Qinghai–Tibet Plateau. CLAS models have good agreement (coherence > 0.9) with Chinese aeromagnetic data at wavelength down to about 100 km (corresponding to spherical harmonic degree n  = 400), filling the usual gap between satellite models and aeromagnetic data. Comparison with aeromagnetic data filtered at 100 km gives good agreement (correlation > 0.95). The residuals between CLAS models and aeromagnetic data are still large (rms > 70 nT), but with most of misfits arising from shorter wavelength fields that the model cannot fit at degree up to 400; such misfit could be reduced by increasing the model degree. We provide a geological example of how the inclusion of satellite data can change the geological conclusions that can be drawn from the magnetic information. However, the two data sets are not completely consistent, future models should start from a reanalysis of the aeromagnetic data and its line levelling to ensure consistency with the satellite model. [ABSTRACT FROM AUTHOR]

The conceptual design of China fusion engineering test reactor (CFETR) is now ongoing. Its toroidal field magnets with a peak field of ∼15 T require a new conductor testing facility with higher background magnetic field to test and evaluate the performance of these conductors. As part of the study of CFETR, the facility named Super X (SUPERconducting eXperiment) is planning to be constructed at Institute Plasma and Physics, Chinese Academy of Sciences (ASIPP) and a conceptual design activity related is going on in parallel. The background magnetic field of the facility is generated by three concentric pairs of split coils with a bore of ∼600-mm diameter, inner coil (IC, peak field of 15.6 T), middle coil (MC, 13 T), and outer coil (OC, 10.5 T) in which IC and MC are connected in series with a nominal operating current of 7.9 kA, whereas OC operates at 13.5 kA. Each split pair coil is made of its own distinctive rectangular shaped cable-in-conduit conductor. The design and preliminary results of electromagnetic optimization and structural mechanical analysis for the background magnet system are presented. [ABSTRACT FROM AUTHOR]

The correlation and synchronization between ground-based and space-based electric field in calm period, is the basis for a comprehensive study of earthquake monitoring. However, it is difficult to study their relevance because of large dissimilarities on data records. The DC-ULF electric field recorded by the DEMETER satellite and the geo-electric field observed in ground-based stations in China were comprehensively analyzed in this paper. The results show that the ionospheric electric field after removing the additional electric field caused by the satellite motion in the magnetic field has a stable annual variation trend; both the annual variation trend and the amplitude of ionospheric electric field above different locations in China are similar. The synchronous, corresponding and similar significant annual variation trends of both ionospheric electric field and geo-electric field in the same direction and with same frequency were found above some locations. The trend displays higher value in summer and lower value in winter. The Sq (Solar quiet) current system is the main source for these phenomena. It is noticed that the shapes and amplitude of geo-electric field for different stations are different, largely due to their individual underground layer conductivity, water level and so on. It is of great significance to explore the correlation and consistency between ground-based and space-based data in order to recognize the anomalies related to the seismic activity and to understand the LAI (Lithosphere-Atmosphere-Ionosphere) coupling mechanism. [ABSTRACT FROM AUTHOR]

Iron-free twin-aperture superconducting quadrupole in the interaction region is a key technology to increase the luminosity of high-energy future colliders, such as the circular electron-positron collider that China will build in the next ten years with a center-of-mass energy of 240 GeV and a small crossing angle of 33 mrad in the interaction region. The final focusing quadrupole QD0, which is 2.2 m away from the interaction point, only has a 72 mm beam separation distance at the front end of the magnet. Because of the tight space, canted cosine theta coil type is the best selection, where the coil can be wound directly on the coil former in a fixed inclination angle. For QD0, the superconducting quadrupole coils for the two apertures are nearly in contact; high-order harmonics will be produced by magnetic field crosstalk and should be canceled out at the design stage. This article will present the design study for a pair of 400 mm long QD0 prototype, where we deliberately introduce some opposite harmonics to optimize the coil configuration so as to cancel out the unwanted harmonics. [ABSTRACT FROM AUTHOR]

The R&D of the central solenoid model coil (CSMC) is preparatory toward the final fabrication of the Chinese fusion engineering test reactor central solenoid coil. CSMC is being designed and partly fabricated in the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). During the process, new manufacturing technologies are developed and some design optimization is proposed. Based on the latest design update, a mechanical analysis is launched to verify whether or not the local components can withstand the shock of the complex loads at the CSMC's steady operation stage. The local components here referred to are the current lead joint and joggle. The current lead joint is the key component to transfer the current into coil modules. The joggle is designed to achieve the smooth transition between the different layers during the conductor winding process. The representative current lead joint and joggle are chosen for the mechanical analysis. The electromagnetic analysis is carried out first to calculate the magnetic field and electromagnetic force density by using the software ANSYS. Then, a one-fifth structural analysis model is built to analyze the stress state of the local components under the combination loads. Finally, the local components are evaluated based on the analytical design. [ABSTRACT FROM AUTHOR]

Surface observations and CHAMP measurement data are employed to develop a three-dimensional surface spline (3DSS) model of mainland China. The magnetic field distribution at the satellite level is then demonstrated using the model obtained. The results of this model are compared and verified by deriving the corresponding two (2DTY) and three-dimensional (3DTY) Taylor polynomial models. Issues such as the removal of disruptive geomagnetic fields, the data gap between the surface and satellite levels, and boundary effects are carefully considered during modeling. We then focus on evaluating the modeling effect of the satellite data. Ten satellite points not involved in the modeling procedure are selected, and the residuals, absolute change rates, and RMSEs of these points are calculated. Results show that the distribution of the magnetic field determined by the 3DSS model is highly consistent with that obtained from the IGRF12 model. Expect for component Y, the absolute change rates of other components are less than 0.5%. Specifically, the RMSE of Y of 3DSS is nearly 60% lower than those of 3DTY and 2DTY; the RMSE of other components of the former are also over 90% lower than those of the latter. This finding implies that the 3DSS model has good performance for modeling satellite data and its results are reliable. Moreover, the modeling effect of 3DTY is better than that of 2DTY. [ABSTRACT FROM AUTHOR]

Very clear coseismic electric and magnetic signals accompanying seismic waves were observed during the 2017 M w 6.5 Jiuzhaigou earthquake, which took place in western China. In order to understand the generation mechanism of these observed signals, we simulate electric and magnetic responses to this specific earthquake based on three mechanisms, namely, the electrokinetic effect, the motional induction effect and the rotation effect of the coil-type magnetometer. We conduct the simulations using a point source model and a realistic layered earth model and compare to the observed data in the frequency band 0.05–0.3 Hz. Our results show that the electrokinetic effect can explain the observed electric fields in both waveform and amplitude, but it cannot explain the magnetic signals accompanying the Rayleigh wave. The motional induction effect cannot explain either the coseismic electric or magnetic data because it predicts much weaker coseismic electric and magnetic fields than the observed data. The magnetic fields resulting from the rotation of the magnetometer agree with the observed data in the waveforms though their amplitudes are two to four times smaller than the observed data. Our simulations suggest that the electrokinetic effect is responsible for the generation of coseismic electric fields and that rotation of the coil magnetometer is likely the main cause of coseismic magnetic fields. The results improve our interpretation of the coseismic electromagnetic (EM) phenomenon and are useful for understanding other kinds of earthquake-associated EM phenomena. [ABSTRACT FROM AUTHOR]

Inversion of magnetic data is complicated by the presence of remanent magnetization, and it provides limited information about the magnetic source because of the insufficiency of data and constraint information. We propose a Fourier domain transformation allowing the separation of magnetic anomalies into the components caused by induced and remanent magnetizations. The approach is based on the hypothesis that each isolated source is homogeneous with a uniform and specific Koenigsberger ratio. The distributions of susceptibility and remanent magnetization are subsequently recovered from the separated anomalies. Anomaly components, susceptibility distribution and distribution of the remanent and total magnetization vectors (direction and intensity) can be achieved through the processing of the anomaly components. The proposed method therefore provides a procedure to test the hypotheses about target source and magnetic field, by verifying these models based on available information or a priori information from geology. We test our methods using synthetic and real data acquired over the Zhangfushan iron‐ore deposit and the Yeshan polymetallic deposit in eastern China. All the tests yield favourable results and the obtained models are helpful for the geological interpretation. [ABSTRACT FROM AUTHOR]

One of biggest obstacles for the development of terahertz (THz) science and technology is the lack of the THz sources, especially, when the requirement of the power reaches to kilowatts. Among all the existing sources, the gyrotron is the most promising one which can generate high-power THz radiation. Recently, a THz detection system is under development in the THz Research Center, University of Electronic Science and Technology of China, Chengdu, China, which is applied for detecting radioactive material. Thus, a 0.68-THz second harmonic gyrotron has been simulated and tested in the center. In this article, we present the theoretical study on the designed gyrotron based on the linear and nonlinear theories. The influences of the different electron beam parameters on the beam–wave interaction are analyzed. The mode competition based on the time-dependent multimode nonlinear theory has also been investigated in the designed gyrotron; it is shown that the operating mode can dominate the mode competition when the gyrotron is working at the optimized operating point. The experiment results show that the output power can reach 3.25 kW with the efficiency 9.26%, at frequency 0.679 THz, when the beam voltage is 39 kV, the beam current is 0.9 A, and the magnetic field is 12.84 T. [ABSTRACT FROM AUTHOR]

A magnetic field configuration of an island divertor for a quasi-axisymmetric stellarator (CFQS) is proposed. The configuration incorporates large islands surrounding the core confinement region. The interface between the core region and the peripheral region of the island divertor is a clear magnetic separatrix similar to a tokamak divertor. The structure of divertor magnetic field lines is very regular without stochasticity and the connection length is sufficiently long for good divertor performance. Such a divertor configuration is produced in the magnetic field configuration for the CFQS device, which is now under construction in China. [ABSTRACT FROM AUTHOR]

With the discovery of the Higgs boson at around 125 GeV, a circular Higgs factory design with high luminosity (L ∼ 1 0 3 4 cm − 2 s − 1) is becoming more popular in the accelerator world. The Circular Electron and Positron Collider (CEPC) project in China is one of them. Machine Detector Interface (MDI) is the key research area in electron–positron colliders, especially in CEPC. Since the e + e − beams collide at the Interaction Point (IP) with a horizontal angle of 33 mrad, the horizontal trajectory will couple to the vertical. Due to the solenoid and anti-solenoid combined field strength quite high, the maximum could be up to 4.2 T, the transverse magnetic field component is also quite high. Thus synchrotron radiation (SR) from vertical trajectory in combined field should be taken into account. And also synchrotron radiation is an important influential factor in the collimator design of CEPC MDI. These two effects are analyzed in this paper. [ABSTRACT FROM AUTHOR]

Electric control of magnetic vortex dynamics in a reproducible way on an ultrafast time scale is a key element in the quest for efficient spintronic devices with low-energy consumption. To be useful, the control scheme should ideally be swift, be scalable, be noninvasive, and result in reliable magnetic switching. Such requirements, particularly the reproducibility of altering the vortex chirality and/or polarity, are not yet met by magnetic vortex switching via external magnetic fields, spin-polarized currents, spin waves, or laser pulses. Here, we demonstrate a novel packaged-skyrmion-mediated vortex switching process driven by a simple sequence of picosecond electrical field pulses via magnetoelectric interactions. Both the vortex chirality and polarity show a well-defined reversal behavior. The unambiguous repeated switching between four different magnetic vortex states provides an energy-efficient, highly localized, and coherent control method for nonvolatile magnetic vortex-based information storage and handling. Magnetic nanomaterials: Ultrafast vortex control for energy saving spintronics Researchers in China and Germany demonstrated a simple method for controlling magnetic patterns that are useful for data storage and information processing. Magnetic nanostructures are engineered as to host swirling magnetic vortices. The vortex intrinsic properties such as the voretx sense of rotations or polarity are well defined and thus are predestinate as digital information carriers. Furthermore, the magnetic nanostructures are readily integrated in existing computers. Chenglong Jia from Lanzhou University, Jamal Berakdar from Martin-Luther Universität Halle-Wittenberg and their co-workers demonstrated how to process the so stored information swiftly by switching both the vortex's sense of rotation and the orientation of its magnetic field using at a simple sequence of ultra-short, low average-energy electric-field pulses. The team believe that their method is scalable, non-invasive, reliable and reversible, fullfing thus important prerequisites for practical implementation. Non-destructive ultrafast control of magnetic vortices by a simple sequence of time asymmetric electric-field pulses. [ABSTRACT FROM AUTHOR]

A new linear plasma device LEAD (Linear experimental advanced device) has been built in Southwest Institute of Physics (SWIP) in China. One of the most notable features of LEAD is the highly flexible and customizable magnetic field configurations, such as highly-uniform field, convergent field, divergent field and cusp field. In this article, we present the design of the magnetic configurations, taking the topology of the magnets, the three-stage vacuum chamber and the magnetic requirements of plasma sources into account. The interplay between the magnetic shielding box of the matching network and the main magnetic field inside the vacuum chamber is evaluated to ensure both a tolerable influence on main magnetic field and an effective magnetic shielding for the automatic impedance matching box in helicon source. [ABSTRACT FROM AUTHOR]

• HTS composite conductors containing stacked HTS tapes are considered to manufacture TF coils in CFETR magnetic system. • The anisotropy of magnetic field of the TF coils is studied. The magnetic field in the different direction is computed in the normal conditions and the fault conditions. • Providing a reference for designing HTS TF magnets. High temperature superconductors (HTS) have been developed over the years and have the better performance. Some conceptual HTS composite conductors have been designed for high field magnets, such as fusion magnets. The magnetic field environment in which the magnet is located must be determined to ensure the safety of the HTS magnet. In this paper, we study the magnetic field distribution of the China Fusion Engineering Test Reactor (CFETR) magnetic system under two plasma equilibrium shapes. In the CFETR magnetic system, HTS composite conductors containing stacked HTS tapes are considered to manufacture the toroidal field (TF) coils. The critical current is related to the direction of the magnetic field in HTS tapes, so we focus on the anisotropy of magnetic field of the TF coils. Sometimes, TF coils of the CFETR magnetic system may operate under fault conditions. Two possible fault conditions are considered: the short circuit in one TF coil and the unprotected quench in one TF coil. We evaluate the magnetic performance of the CFETR magnetic system under fault conditions and also analyze the magnetic field of the TF coils in different directions under fault conditions by the finite element method. This provides a reference for the design of the HTS TF magnets. [ABSTRACT FROM AUTHOR]

In this work we introduce a system pipeline for the analysis of earth’s electromagnetic field that is used to analyse precursors to earthquakes. Data gathered by the Swarm satellites are used to present the utility of our system. Our objective is to provide a streamlined method to analyze electromagnetic data over a region and investigate the relationship of precursory signals to seismic events. The process follows three distinct stages: data extraction, data pre-processing and anomaly detection. The first stage consists of the region selection and data extraction. The second stage consists of four different pre-processing methods that address the data sparsity problem and the cause of artificial anomalies. The last stage is the Anomaly Detection (AD) of the Swarm satellite data, over the investigated region. The different methods that are implemented are known to perform well in the field of AD. Following the presentation of our system, a case study is described where the seismic event of 6.2 Mw is in Ludian, China and occurred on 3rd August 2014. The event is used to present the usefulness of our approach and pinpoint some critical problems regarding satellite data that were identified. [ABSTRACT FROM AUTHOR]

In DC systems, DC resistive type superconducting fault current limiters (R-SFCLs) can respond within a few hundred milliseconds and limit the fault current to a very low level to protect the power equipment in DC systems. The main part of R-SFCLs are superconducting tapes. When short-circuit faults occur in the system, the superconducting tapes will quench and become a large quenched resistor to limit the fault current. The surrounding magnetic fields and the magnetic fields caused by the superconducting tapes itself influence the quench characteristics of the superconducting tapes of R-SFCLs. Thus, the current limiting characteristics of R-SFCLs will also be affected. Until present, very few studies have investigated the effects of magnetic fields on quench characteristics of superconducting tapes for DC R-SFCL. The objective of this paper is to obtain the effects of magnetic fields on quench characteristics of superconducting tapes for DC R-SFCL. Two different kinds of YBa2Cu3O7-δ (YBCO) tapes are studied under a permanent magnetic field of 0, 42.4, 75.9, 122.9 mT, respectively. One is from Shanghai Superconductor Technology Co., Ltd., Shanghai, China, type ST-12-L (named SC_SH) and the other is from American Superconductor Inc. Boston, MA, USA, type 8602 (named SC_8602). The research results show that the magnetic fields influence both the amplitude and the rising rate of the quenched resistance of an SC_SH tape. Under the same magnetic field, both the speed of quenching and the quenching resistance of SC_SH tape are larger than them of SC_8602 when the prospective current exceeds 800 A. Thus SC_SH tape can limit the fault current faster and to a lower level. [ABSTRACT FROM AUTHOR]

The evolution correlation between the North China Craton (NCC) and the Indian Shield (IND) is very important for plate reconstruction. Recently, more and more research results show that the NCC and IND had been pieced together in the Paleoproterozoic. In order to analyse the correlation between the NCC and IND, we use the latest gravity and magnetic data to study deep geophysical characteristics of the NCC and IND respectively, and we also use a two‐dimensional discrete wavelet transform method to discuss the division scheme of the basement tectonic unit in the Paleoproterozoic at the point of gravity and magnetic field. On the basis of gravity and magnetic anomalies, the NCC is divided into the Eastern Block, Western Block, and the Trans‐North China Orogen, which are further divided into the secondary tectonic zones and blocks. The IND is divided into the Southern Block, the Northern Block, and the Central Indian Tectonic Zone, and they also are further divided into secondary tectonic zones and ancient cratons. On the basis of that, according to the four Paleoproterozoic plate assemblage schemes proposed by predecessors, we compared the geophysical characteristics and the correlation through the regional gravity and magnetic anomalies between the two continents. The results show that the faults and tectonic boundaries in the Trans‐North China Orogen of the NCC correspond well to those in the Central Indian Tectonic Zone of IND. Moreover, the gravitational and magnetic anomalies in the Eastern Block of the NCC are quite similar to those in the Southern Block of IND, which shows that the NCC and IND might have been pieced together during the Paleoproterozoic. The geophysical result that verifies the correlation between the NCC and IND based on gravity and magnetic fields provides the evidence for Paleoproterozoic plate reconstruction and constrains the assembling patterns between the NCC and the IND. [ABSTRACT FROM AUTHOR]

A 140 GHz high power gyrotron with a gradually tapered cavity has been investigated and formed at the University of Electronic Science and Technology of China recently. After the study of cold cavities, a set of operating parameters of the optimized cavity is obtained as the TE29,8 mode is selected as the operating mode. The startup-scenarios of the potential competition modes have been investigated by simulation, which is based on a kind of quasi-self-consistent nonlinear theory for gyrotrons. After a lot of calculations, a better startup scenario is confirmed. Under the conditions that the beam voltage varies in 5 kV steps and the beam current and DC magnetic field are of 45 A and 5.64 T, respectively, the gyrotron with the operating mode TE29,8 brings out a theoretical power level of 1.2 MW at 140 GHz, corresponding to an overall efficiency of 35.5%. Meanwhile, the powers of parasitic modes are very low when the gyrotron operates at the proper parameters. At the same time, to study the limit state and its parameters of the designed gyrotron, further research has been carried out. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pickled kohlrabi texture showed typical twice "increase-decrease" during pickling. • Texture change mechanism were studied by in situ immunofluorescence, LF-NMR and TEM. • Water state contributed to texture increase–decrease at the early pickling stage. • The degradation of cellular structure and pectin led to the final texture decrease. Pickled kohlrabi is a traditional and favored vegetable product in China. During pickling, the hardness, springiness, and chewiness of kohlrabi all experienced a typical change with twice "increase-decrease" trend. However, little is known about its mechanism. In this study, in situ analysis including immunofluorescence, low field nuclear magnetic, and transmission electron microscopy were used to explore the effects of cell wall pectin, water state, and cellular structure on kohlrabi texture changes during pickling. Results revealed that at the early stage, due to the rapid loss of water after three times salting, the cells shrank and the interstitial space reduced, resulting in the first increase on kohlrabi texture. Subsequently, the dehydration-rehydration caused by the first brine processing resulted in the first decrease on kohlrabi texture. Then under the action of PME enzyme, more low-esterified pectin was produced, and chelate-soluble pectin with more branched structure was further formed, leading to another elevation of the sample texture. As the pickling continued, under the combined action of PG and PME, the molecular weight of pectin was decreased and the rigidity of the cell tissue was destroyed, caused kohlrabi texture continued to decline. These researches could provide important information and guidance for better maintaining the texture of pickled vegetables during processing. [ABSTRACT FROM AUTHOR]

Magnetotactic bacteria (MTB) can rapidly relocate to optimal habitats by magnetotaxis, and play an important role in iron biogeochemical cycling. This study aimed to evaluate the contribution of the external magnetostatic field to the diversity of MTB in freshwater sediments from Yangtze River (Changjiang River, CJ), Chagan Lake (CGH) and Zhalong Wetland (ZL). The magnetic field intensity was tightly associated with the community richness of MTB in CJ, whereas it was closely related to the diversity of MTB in CGH and ZL (p < 0.05), elucidating a significant variation in the community composition of MTB. Magnetic exposure time appeared more significant correlation with community richness than diversity for MTB in CJ and CGH (p < 0.05), while an opposite relationship existed in ZL (p < 0.01). Herbaspirillum (93.81–96.48 %) dominated in the sediments of these surfacewatesr regardless of waterbody types, while it shifted to Magnetospirillum in ZL under 100 Gs magnetic field. The network connectivity and stability of MTB deteriorate with the increase of magnetic field intensity. Functional analysis showed that the Two-component system and ABC transporter system of MTB obviously responded to magnetic field intensity and exposure time. Our findings will pave the way to understanding the response mechanism of MTB community in freshwater sediments to the external magnetostatic field. [Display omitted] • MTB widely exist in Changjiang River (CJ), Chagan Lake (CGH) and Zhalong Wetland (ZL) of China. • Dominant Herbaspirillum and Magnetospira occur all sediment samples. • Magnetic field intensity and exposure time both affect MTB diversity and richness. • Network connectivity and stability of MTB deteriorate as magnetic field intensity. • Metabolic function and ABC transporter system visibly respond to magnetic field. [ABSTRACT FROM AUTHOR]

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