Multilayer Shield Research Articles

Minimizing magnetic fields of the low-noise MnZn ferrite magnetic shield for atomic magnetometer

Several modern precision measurements require a low-noise magnetic shield composed of a MnZn ferrite shield and a multilayer µ-metal shield. However, the residual magnetic field and gradient reduce the performance of the low-noise magnetic shield. An appropriate demagnetization operation is crucial for obtaining a lower residual magnetic field and gradient. This study proposes an improved demagnetization scheme in which the toroidal coil and the solenoidal coil are employed simultaneously, while the ferrite and µ-metal shield layers are wound separately. This allows for a residual field below 0.6 nT and a gradient lower than 0.5 nT cm−1 to be obtained along all three axes within ±20 mm at the center, which is significantly lower than the results published in previous studies. The low-noise magnetic shield used in this study composed of a MnZn ferrite shield with an inner diameter of 112 mm, an outer diameter of 140 mm, and a height of 225 mm, and a five-layer µ-metal shield. This study considerably improves the performance of the low-noise magnetic shields. The proposed scheme can increase the sensitivity of the spin-exchange-relaxation-free atomic magnetometer by approximately 1 fT Hz-1/2. This study can help apply the low-noise magnetic shield in various fields more conveniently, such as low-field nuclear magnetic resonance detection, atomic gyroscope, and in cutting-edge physics research.

Энергоемкость тканевых материалов при ударном нагружении

Space orbital stations operations support consists an adoption of meaningful measures to protect space station against impacts of space debris and meteoroids. This goal can be reached by using multilayered protection shields that are made with the fabric material layers. Shields designing and modeling requires specific characteristics that define energy absorbed volume by the fabric destruction under impact. The paper describes the methodology and experimental determination method for absorbed energy volume results by using multilayer fabrics of orbital manned stations shielding constructions under distributed impulse loading caused by the space debris impacts. The energy absorbed volume by the multilayer fabrics is obtained from the experiments by analysis of specimen and flat metal projectile impact. Projectile was accelerated by the air gas gun. The obtained experimental determination results of energy absorbed volume in pressure range up to 1,5 GPa are given. Using the model of fabric as a porous material its energy absorption volume dependence in pressure range up to 10 GPa and compared with experimental data. It is shown that for materials with high porosity absorbed energy volume against pressure dependence is close to linear. Corresponding asymptotic dependence for materials with high porosity under the high pressure is obtained.

Composition design and anticorrosion performance optimization of zinc molybdate pigments

Exploring the design of zinc molybdate pigments to optimize their properties is an interesting work. Three types of zinc molybdate, amorphous ZnMoO4, Zn5Mo2O11·5H2O, and β-ZnMoO4, were synthesized by regulating the synthesis conditions. Experimental results revealed that the monoclinic β-ZnMoO4 possessing a distorted octahedral [ZnO6]/[MoO6] cluster structure exhibited the optimal anticorrosion and photocatalytic properties. Then, the synergistic anticorrosion mechanisms of β-ZnMoO4 were proposed: multilayer shielding layer protection and photoelectrons suppression effect of anodic reaction. Next, three surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP-K30), were employed to modulate the growth of β-ZnMoO4. Experimental data showed that the induced modulation of PVP-K30 could greatly increase the specific surface area and photoelectrons production efficiency of β-ZnMoO4. Besides, the charge transfer resistance of β-ZnMoO4-P (synthesized with PVP-K30) was 25.58 times higher than that of β-ZnMoO4-0 (synthesized without surfactant) after 72 h of immersion in 3.50 wt.% NaCl solution. Consequently, the design strategy of zinc molybdate pigments provides a reference for the improvement of performance of other inorganic anticorrosion pigments in industry.

3DGShield: A new 3D gamma ray shielding code for arbitrary source and shield geometry based on point kernel technique

3DGShield, A new 3D gamma ray shielding code, based on the method of point kernel technique, has been developed for arbitrary regular & irregular shaped source and shield geometries. The 3D geometry modeling and its mesh generation are performed using Gmsh, a free open source finite element mesh generation software. The output of the Gmsh software is in Gmsh MSH (.msh) file format which will be used as an input of geometry description of our code. The salient features of 3DGShield are (i) ability to handle any type of complex source geometries including regular source shapes like point, line, disc, box, cylinder, sphere, hexagonal cylinder, cone etc. and irregular source shapes like pieces of broken glass, piece of brick etc., (ii) handling discrete as well as distributed photon energy sources, (iii) modeling any kind of regular and irregular complex multilayered shield geometries, (iv) having provision to export the output results into ParaView, an open source data analysis and visualization software, for quick visualization and analyzing of the results. Buildup factor is the correction factor which takes account the contribution of scattered photon. Various appropriate multilayer build-up factor formulas have been incorporated in our code. Out of these, the most popular methods are Blizard's method, Goldstein method of an effective atomic number and Broders's method. Verification and validation of the code have been done by a number of benchmark problems available in literature. The results are presented in this paper which demonstrate the accuracy and efficiency of the code in complex geometries. This code is written in Python-2.7 language and compatible both in Windows and Linux operating system.

An embedded capacitive sensor for in-situ angular detection of micromotor

An embedded capacitive sensor in traveling wave ultrasonic motor is proposed for angular detection. Equivalent circuit model of the system is well studied that correlation between sensor structure, parasitic parameters and the property of detection signal is found. Sensor structure is optimized with innovate structural design including multi-layer shielding, planar isolation and differential detection design. The signal-to-noise ratio of the detection signal is found up to 40 ​dB and the angular detection accuracy during step motion is less than 0.1°.

Multilayer magnetic shielding for testing a superconducting single-flux-quantum circuit chip in liquid helium dewar

In order to reduce the influence of environmental magnetic field on the test of superconducting single-flux-quantum (SFQ) circuit chip in a liquid helium dewar, a multilayer magnetic shielding structure is designed to provide a clean magnetic field lower than 50 nT and achieve a shielding effectiveness higher than 60 dB. The magnetic shielding structure consists of three cylindrical layers with uniform 1 mm thickness. The first inner layer is made of NbTi which works as a strong diamagnet shell, while the outer two layers are made of permalloy which has high permeability at helium temperature. The superconducting quantum interference device (SQUID) was used to test the shielding performance of the structure under low frequency (0.1–100 Hz) magnetic interference at helium temperature. The results show that the radial and axial shielding effectiveness (SE) are about 80 dB and 68 dB, respectively, indicating that the multilayer structure has good shielding performance and can be used in the testing system of superconducting single-flux-quantum circuit chip.

Research on shell magnetic shielding based on finite element method

In this paper, several different magnetic shielding schemes are proposed, the finite element static magnetic field analysis method is introduced, and the finite element method is used to simulate these methods. According to the calculation results, we analysed different magnetic shielding schemes, the results show that the opening will significantly reduce the magnetic shielding efficiency; under the same materials, the multi-layer magnetic shielding effect is significantly improved; when the opening is parallel to the direction of the magnetic induction intensity, the magnetic shielding has a better effect; when the direction of the magnetic field is unknown, the two-layer magnetic shielding opening direction can be orthogonal to improve the magnetic shielding effect.

A 3D FDTD approach for calculation of geomagnetically induced currents considering complex multilayer ground structure

A rigorous finite difference time domain (FDTD) method is proposed for accurate and fast calculation of geomagnetically induced currents (GICs). The proposed method takes into account complex 3D ground structures. The effect of multilayer stratified ground, shield wire and different excitation sources on GICs are evaluated. It is shown that the ground stratification can significantly affect GICs. The increasing effect of shield wires on GICs are also presented. It is also found that the sheet-current electrojet yields GICs with lower amplitudes compared to the line-current electrojet.

Electromagnetic shielding performance of copper and silver-plated hybrid yarn based multilayer fabrics in C & X band frequency range

In the present study, a strategic designing of multilayer shield was planned to enhance the multiple reflection phenomenon to achieve maximum absorption properties in microwave frequency (C & X band) range. Multi-layer EMR shields were developed using pure cotton fabric and conductive woven fabrics, incorporated with copper- based & silver-plated hybrid yarn. First of all, single layer fabrics were produced in five variants, nomenclature as L1A (pure cotton) L1B, L1C (copper-based hybrid yarn), LS1B and LS1C (silver plated hybrid yarn). These five variants were used to prepare four sets of double & triple layer fabric. In both double and triple layer composition, L1A fabric (pure cotton) was used as top layer followed by B and C series fabrics, containing copper and silver-plated hybrid yarn. The EMSE performance in C and X band frequency range of single layer, double layer and triple layers in terms of scattering parameters S11(reflectance) & S21 (transmittance) in vertical and horizontal wave polarization was studied. It was found that number of layers, layer composition, orientation of metallic yarn, frequency and EM wave polarization have significant influence on overall electromagnetic shielding effectiveness.

A Novel and High-Precision Method for Calculating the γ-Ray Build-Up Factor for Multilayer Shields

In the field of radiation protection, the point-kernel code method is a practical tool widely used in the calculation of 3-D radiation field, and the accuracy of the point-kernel integration method strongly depends on the accuracy of the build-up factor. It is well known that calculation of the build-up factor for single-layer shields is composed of single material, but it is very complicated to calculate the build-up factor for multilayer shields (MLBUF). Recently, a novel and high-precision method based on the deep neural network (DNN) for calculating MLBUF has been proposed. In this paper, the novel method is described completely by slab models. Through the study of photon transport in multilayer shields, the parameters that mainly affect the calculation of build-up factor are analyzed. These parameters are trained by DNN as the input vectors, and the build-up factor for multilayer shields is predicted based on the trained DNN. The results predicted by DNN confirm that the method can calculate the build-up factor for multilayer shields quickly and accurately. The method has been preliminarily applicated into a 3-D radiation field calculation software, and it has proved that the method for calculating MLBUF has a broad application prospects in 3-D radiation field calculation.

ИНТЕГРАЛЬНАЯ ПРОМЫШЛЕННАЯ СИСТЕМА УТИЛИЗАЦИИ ТЕХНОГЕННЫХ ОТХОДОВ ГОРНЫХ ПРЕДПРИЯТИЙ, ТЕРРИТОРИАЛЬНО ОБЪЕДИНЁННЫХ

At present, there is a need for import substitution (including technologies) in Russia, so the manuals development and regulation of the best available technologies (BAT, Best Available Technologies) are underway. BAT manuals, for example, for the mining industry are basic documents that provide a step-by-step description of BAT, ensuring compliance with obligatory environmental performance indicators. However, these are isolated, unrelated short versions that do not allow for a comprehensive solution to the problems of available mineral resources (AMR) deficit and reduction of environmental degradation risks. To solve the above problems, it is necessary to develop an integrated system for the disposal of man-made waste from mining and mining processing enterprises, geographically united, in order to identify, select effective technologies from alternative proposals and their implementation. The purpose of the study is to develop an integrated system for the disposal of technogenic waste from mining enterprises that are geographically united. Research objectives: study of waste disposal facilities included in the State Register of the Russian Federation; development of a technological scheme for the joint processing of technogenic raw materials of various types; development of a stationary cuvette for year-round heap leaching (KV) of gold in the cryolithozone; conducting experimental studies of KV gold with an effective reagent complex; development of an integrated industrial system for the disposal of technogenic waste from mining enterprises, geographically united; development of alternative options for the production of gold in order to choose an effective technology, depending on the nature of gold mineralization and the form of finding the precious metal in man-made waste. The authors have scientifically substantiated and developed the variants of the integrated industrial system of the closed cycle, using mobile operatively tunable flow lines consisting of independent modules for technogenic waste processing of Darasunsky mine - the enterprise for extraction and ore enrichment of Darasunsky, Teremkinsky and Talatuysky gold deposits (Tungokochensky and Transbaikal regions). According to the cadastre of technogenic accumulations, the sources of mine wastes with the volume of 14410.2 thousand tons are waste dumps of overburden rocks and poor ores, technogenic raw materials of tailing dumps, other accumulations of technogenic raw materials. Experimental studies of gold heap leaching (HL) by the reagent complex including solutions of sodium cyanide and hydrogen peroxide in the ratio – H2O2:NaCN=10:1 have been carried out. Optimal technological parameters of ore preparation and gold leaching process from waste pelletized granules of different types at a ratio of 1:0.5:0: 5 are established, accordingly, out of balance ores of the Talatuy deposit (βAu – 0.7 g/t), underlaid tailings (βAu – 1.45 g/t) and tailings of the current ore processing of Darasunsky gold concentration plant (GCP) (βAu – 0.3 g/t). Gold recovery has amounted 87.1%. In order to implement year-round heap leaching in the cryolite zone, a deepened concrete ditch with multilayer shielding of the upper surface of the stack by injecting warm air through specially equipped perforated vinyl pipes has been installed and a special pelletized granules placement has been carried out. After neutralization KV waste has been proposed to be used in the road construction industry. The industrial system developed by the authors makes it possible to carry out all year round KV, to commercialize utilization of man-caused deposits, both for a long conservation period and the current production and processing, to improve the environmental safety of the city-forming enterprises of the mining cluster. Alternative options are proposed in order to choose an effective technology

Simulation of a Grid Multi-Layer Shield to Reduce the Magnetic Field of Power Lines

Seeing the harmful effects of the magnetic field on human health, the task of reducing the magnetic flux density in places of people long-term stays near power lines is actual. One of the ways to solve this problem is a passive shielding.Analyze of shielding efficiency was performed by computer simulation using COMSOL Multiphysics software. It was created a 2D model of a three-phase 330 kV overhead power transmission line and the research area, which is a conventional residential building located outside the security zone.The magnetic field was simulated and the value of magnetic flux density in the research area was determined for cases of using a passive grid electromagnetic screen of different configurations. The efficiency comparison of different shields was performed qualitatively on the color and contour maps of the magnetic flux density distribution in the research area and quantitatively on the average value of the shielding factor.The efficiency of a single layer vertical shield, located on the building wall closest to the power line, and a horizontal shield, located at the average height of the building, were compared. It is shown that with the same metal content (the same diameter of the shield conductors and the same number of them) the vertical shield is more efficient than the horizontal, but it also cannot always provide a safe level of magnetic flux density.The configuration of the multilayer shield, which can be placed in overlapping between floors of the building, is presented. It is shown that with the same metal content such shield can provide better reducing of the magnetic field than a single-layer, and it is able, under the same conditions, to decrease the magnetic flux density to a safe level. But this configuration has one disadvantage. In the part of the building closer to the power line (approximately 4 m from the wall) the value of magnetic flux density exceeds the safe level. It is possible to reduce the width of such zone due to a denser placement of shield conductors. It was also found that the placement of the shield horizontal layers on each floor is more effective, i.e. as evenly as possible over the research area.In addition, a research the dependence of the shielding factor of the multilayer shield on the conductor’s diameter and the distance between them. It is shown that such shield allows reducing the average value of magnetic flux density in the research area hundreds of times, although with a fairly large metal content.

Experimental and numerical investigation on the perforation resistance of double-layered metal shields under high-velocity impact of soft-core projectiles

Multi-layered metal shields have been extensively investigated in the past, mainly studying the effect of layering, spacing and order of plates of different materials. However, at present is not feasible to predict the effect of layering and spacing for a particular case but only general pattern can be considered. Some investigations based on numerical simulations showed that the multi-layered configuration made by layers of different metals could be a promising solution in terms of weight reduction of the shield but, different authors obtained contradictory results and comprehensive experimental investigation is still missing. Thus, the scope of this study is to evaluate the perforation resistance of double-layered metal shields constituted by a high-strength steel and an aluminum layer when impacted by a soft-core projectile. It was found that the multi-layered configuration constituted of two layers of different metals, is less efficient than the monolithic configuration. Furthermore, numerical models were developed to increase the understanding of the problem. It was necessary to use an alternative to the commonly used FE method to model extreme deformation occurring in soft-core projectiles in such kinds of scenario. In particular, the SPH method was implemented providing a detailed parametric study of the most relevant numerical parameters. The SPH method was thus exploited to study different configurations of the double-layer target, and it was found that the specific ballistic energy depends on the ratio between the two layers of the target.

An improvement to the Kalos’ formula for double layer gamma ray exposure buildup factors for shielding materials of nuclear and radiological facilities

Gamma ray exposure buildup factors (BUFs) are used in point kernel method based shielding codes to estimate the scattered radiation dose rate. BUFs computed by assuming single material for multi-layer shielding configuration either overestimate or underestimate the dose rates. Hence, BUFs computed based on stratified shielding configuration give better estimates of scattered dose rate and provide scope for further optimization of shielding thickness. In nuclear and radiological facilities, shielding materials such as concrete (Con), iron (Fe), lead (Pb), and tungsten (W) are normally used as single or multi-layer shields. For the first time, buildup factors estimated based on Monte Carlo simulations (MCS) for double layer shielding configurations (DBUFs) of W and Fe, W and Con, Pb and Fe, Pb and Con, and Fe and Con are reported. The estimated DBUFs are compared with the values obtained using the empirical formulae published by several authors. A significant variation up to 40% is observed between MCS and empirical formulae. Hence, the correction factor in the empirical formula of Kalos’ is modified and standardized by carrying out further computations for various double layer shielding configurations and energies. Radiation shielding experiments performed to validate the MCS results are presented.

Optimization Analysis of Electrostatic Cloaking Problems

Under consideration are the inverse problems of electrostatics which arise in designing two-dimensional multilayer shielding and cloaking devices. Using optimization, we reduce these inverse problems to the finite-dimensional extremal problems in which the roles of control parameters are played by the constant dielectric permittivities of the layers. Basing on particle swarm optimization, we develop some numerical algorithm for solving these problems. We also show that the devices designed by the algorithm have the highest cloaking efficiency and simplicity of technical implementation.

A Feasibility Study to Reduce the Contamination of Photoneutrons and Photons in Organs/Tissues during Radiotherapy

Introduction: Due to out-of-field effects in radiation therapy, the determination and reduction of both unwanted photon and photoneutron doses are essential for the reasonable assessment of the risks to healthy tissues. Material and Methods: By the application of a multilayer shield throughout the phantom and using two models for photoneutron and photon sources, doses were estimated in a 15-MV linac in tissues and organs. Different neutron moderators were used, and the best materials, such as polyethylene, polystyrene, polyvinyl chloride, paraffin, and water, were reported for shielding purpose. Boron carbide and steel were utilized as neutron and gamma absorbents. Various lengths of the shield in line with phantom stature were also assessed in this study. Results: Except for the target organ, with the shield throughout the phantom, both photoneutron and photon doses approximately reduced by 57-89% and 88-95%, respectively. Extra photoneutron dose in the photon source was also reported due to the shield. Then, unwanted doses, especially photon dose remarkably decreased with increasing the steel thickness. The smaller dimensions of the shield caused also a considerable reduction of the photoneutron and photon doses in the phantom. Conclusion: The application of a multilayer shield reduces the photon dose remarkably in healthy tissues. Therefore, it is recommended to use shielding materials to decrease photoneutron and photon doses, which can cause a reduction in the risk of secondary cancer. Due to the relatively high mass of the shield, it is necessary to design a proper device to maintain and move the structure.

Py-MLBUF: Development of an online-platform for gamma-ray shielding calculations and investigations

Detailed information about various gamma-ray shielding parameters (GSP) is required to investigate the building's gamma-ray shielding efficacy. The computer plays an essential role in such investigations by calculating the GSP. The multi-layered shields provide better shielding efficacy than the single-layered protectors. This work aims to describe the development of an online-platform to calculate 36 GSP for both types of shields. A computer code for the platform has been written in Python and named as Py-MLBUF. It calculates the GSP, in the energy range 0.015–15 MeV. One can use the developed platform free of cost from https://pymlbuf.pythonanywhere.com. It is accessible from computers and smartphones. The added features like fast calculation speed, higher accuracy, graph plotting capability, analyzing and suggesting an improvement in shielding efficacy, and sending the results via e-mail, make it unique. Py-MLBUF will serve as a free interactive educational tool to provide free research consultancy in improving radiological safety.

Low-Frequency Electromagnetic Shielding and Scattering of Multiple Cylindrical Shells

Emerging additive manufacturing methods facilitate the creation of enclosures with tailor-made shielding and scattering performance by using multiple conductive and dielectric layers. For a first analysis an elongated housing, with a cross-section small compared to the wavelength of the impinging electromagnetic field is replaced by an infinitely long multilayered cylinder. In a previous paper, we concluded that existing solutions of the Maxwell equations for this configuration are not accurate in calculating scattering. This also negatively impacts results for multilayer shielding. This article proposes a fast, time-harmonic formulation based on a combination of Bessel and Hankel functions as solution to the Helmholtz equation. Both electric and magnetic fields are considered and solutions are obtained independently for transversal and longitudinal source fields. These can be superpositioned to describe arbitrary source fields. The system of equations defined by the boundary conditions of the multilayer problem is solved via Gaussian elimination which can easily be automated with standard MATLAB or Octave functions. Results are compared to known approaches and applied to a dual-layer use case. The latter shows that shielding and scattering performance improves significantly with multiple layers compared to a single layer with equivalent thickness both for transversal and longitudinal fields.

The Faraday Shields Loss of Transformers

Faraday shields are widely used in high-frequency transformers to conduct the common-mode (CM) current to the ground. They are normally located in the high magnetomotive force (MMF) region, where severe eddy currents are induced and contribute considerable magnetic field losses. In this article, an analytical procedure is presented for the magnetically-induced loss in Faraday shields. It is originally derived from shields of foil conductors. Then, it is extended to different shields with round and Litz wire, and different configurations, e.g., multilayer shields, interleaved windings, and coaxial transformers. It is verified by the finite element method (FEM) and experimental results in six case studies. Moreover, the criteria to determine the losses of Faraday shields is given and a design procedure is presented to reduce the shield losses at a certain level while keeping the functionality. Finally, a case study is provided to verify the shield design procedure on a 100-kHz transformer.

Experimental characterization of multi-layer 3D-printed shields for microsatellites

In recent years, innovative processes such as additive manufacturing are finding application in the satellite industry, allowing solutions of which implementation could have been difficult or expensive using traditional manufacturing techniques. In the framework of the EU H2020 ReDSHIFT project, new 3D printed shields were developed for microsatellites protection: (1) a multi-shock panel comprising four equally-spaced 3D printed bumper layers, (2) a two-walls panel with outer bumper layers sandwiching a corrugated core, and (3) a hybrid panel with three equally-spaced bumpers, and a fourth corrugated bumper sandwiched between two of them. These shields were evaluated with respect to their resistance to hypervelocity impacts of mm-size debris expectable in the LEO environment. This paper presents the results of HVI tests carried out at the University of Padova on the proposed panels: debris-shielding properties were evaluated with respect to the damage on targets and witness plates placed behind them. Debris clouds resulting from panels perforation were also observed qualitatively through high-speed imaging. Compared to standard honeycomb panels, all the proposed shields showed improvements in terms of debris shielding.