Shielding System Research Articles

Flexible PTFE/MXene/PI soft electrothermal actuator with electromagnetic-interference shielding property

In recent years, soft electrothermal actuators (ETAs) have attracted great concern because of their potential applications in biomimetic intelligent devices, soft robotics and aerospace engineering. However, achieving the simultaneous optimization of low-voltage actuation, ultrafast preparation and highly integrated functionality are main challenges to the development of ETAs. Herein, a flexible, hydrophobic, mechanically robust and electromagnetic-interference (EMI) shielding PTFE/MXene/PI soft ETA is constructed through a very simple and fast “cutting and sticking” method by taping PTFE and PI tapes onto the surface of MXene film. The commercially available PTFE and PI tapes endow PTFE/MXene/PI sandwich structure with ideal mechanically robustness and hydrophobic self-cleaning function, thus it can work in different environments. Remarkably, PTFE/MXene/PI sandwich structure shows an outstanding EMI shielding ability with the maximum SET value of 44 dB owing to the high electrical conductivity of MXene film. More importantly, the PTFE/MXene/PI sandwich actuator can bend from PTFE side toward PI side under the electrical stimulus, because the excellent electrothermal MXene layer is sandwiched between the two tapes with large difference in thermal expansion coefficients. Under a 6 V low voltage, the actuator can generate heat energy with the maximum saturation temperature of 110 °C and large bending deformation with the maximum bending angle of 122° within 40 s. Interestingly, the PTFE/MXene/PI structure can be designed and manufactured in different shapes and configurations upon actuation, such as the “S” shape and four-finger gripper. At last, a smart shielding curtain with the combination of actuation properties and EMI shielding performance is finally developed as a principle of concept, which further indicates the multifunctional PTFE/MXene/PI ETA can be widely applied in smart EMI shielding system and soft robotic devices.

Electromagnetic Field Shielding in Incubators

Purpose: Cell experiments are vitally dependent on CO2 incubators. The heating system of usual incubators result in undesirable induction of Electromagnetic (EM) fields on cells that result in decreased accuracy in bio-electromagnetic tests. EM shields can cause a considerable decrease in the stray fields and eliminate the undesirable induction. Materials and Methods: CST-2019 is used for simulations. five different shielding systems have been examined in this paper. We try to modify shape and material used for shielding to achieve better result. (Iron, Mu-Metal, steel). Results: We introduce a simple practical design, together with variations of previously reported ones, and numerical evaluation of their magnetic field attenuation. Conclusion: The targeted design decreases the field within the shield to about 0.03 times of the incident magnetic field, while having holes for air and CO2 exchange.

Разработка вакуумной дугогасительной камеры для одноразрывного вакуумного выключателя на 110 кВ

Requirements for high-voltage vacuum circuit breakers for networks with a grounded neutral, which are stemming from the prospects of using vacuum circuit breakers in networks with the solidly grounded neutral are formulated. The arch chute design for a 110 kV single-break vacuum circuit breaker that takes into account the occurrence of repeated breakdowns is developed. The shielding system equalizes the voltage over the chute casing, decreases the electric field intensity at the “triple point”, protects the casing dielectric from becoming dusted with metallic contact parts erosion products, prevents the occurrence of cascade breakdown between the contact parts and central shield, and eliminates a possible decrease of the chute electric strength as it gradually works out its switching life. It is shown that the chute design includes measures to prevent the possibility of repeated breakdowns during disconnection up to class С1 according to GOST 52565-2006. It has been proven that for vacuum arc chutes for class С2 (for switching a capacitive load) it is necessary to develop a chute with two breaks between the contact parts or to connect two vacuum chutes in series. The shielding system adopted in the chute rules out the possibility of ceramic casing to become metallized, which decreases the chute electric strength as it gradually works out its switching life, and the vacuum arc transfer to beyond the inter-contact gap boundaries onto the central shield, the burnout of which results in that the vacuum arc chute loses its tightness and fully loses its functional properties.

Modelling of Electromagnetic Fields for Shielding Purposes Applied in Instrumentation Systems

In any sensory system, the Electromagnetic (EM) shielding of the channel-carrying signal is a fundamental technique to provide a noise-immune measurement system. Severe failures and uncertainty may occur if the external EM fields interfered with the measurements. Typically, the shielding is realized by enclosing the channel-carrying signal with thinconductive hollow structures. However, with such structures, it is required to provide access to the interior components from the outside, for wires' connections, or better heat dissipation. This can be considered as a weakness in such the external magnetic fields can penetrate through the shielding structure. In this paper, the EM shielding effectiveness is considered for long hollow-cylinder structures with slots. The induced eddy current in thin-conductive shielding systems with slots together with the magnetic fields at different conditions are modeled. The objective is to determine the impact of the integrated slots along with the structure. The influence of the slots' sizes (α) and position relative to the excitation magnetic field (i.e., the declination angle (β)) are investigated to evaluate the shielding effectiveness by means of the determination of the shielding factor. The results reveal the inherent relationship between the shield parameters and shielding effectiveness. The shielding effectiveness deteriorates by the slots' integration within the shielding surface. However, decreasing the size of the slots improves the shielding, significantly, towards the shielding effectiveness of the continuous cylindrical structure. Additionally, utilizing the symmetry in the structure positioning the slots in the direction perpendicular to the magnetic field flux improves the shielding effectiveness, drastically. Such a model can be considered to evaluate the degree of effectiveness or success of integrating opening slots within the shielding structure, which can be applied to different types of instrumentation systems specifically at the sensor-electronics interface.

Design and evaluation of low power wireless charger concept

This article deals with the concept proposal of the wireless charger for low power application areas. As wireless charging undertakes popularity, initially the state of the art within application area is realized, while main focus is given on the personal e-mobility mean of transport. The most suitable configuration of power electronic system is initially discussed, whereby several power converter stages are equipped within physical prototype as well. The biggest attention is given on the construction of the coupling elements, while design procedure is supported by the finite element analysis. The modelling of coupling coils element enables to improve physical model by the shielding system due to achievement of the required operational characteristics defined by bio-combability standards. The experimental part of the paper is discussing investigation of the operational characteristics of the whole wireless charging system. Here the efficiency characteristics in dependency on output power and transmitting distance is evaluated. Received results confirm suitability of the presented design approach and practical use of proposed wireless charger for e-scooter or e-bikes applications.

Length estimation for loop shielding system when decreasing cable line magnetic field

This paper deals with a mitigation of a cable line magnetic field by a loop shield. Approximate analytical expressions for a phasor and rms value of a magnetic flux density in a shielding area are developed. I give a clear physical interpretation for the obtained relations and the parameter γ that they contain. The limiting case γ=1 is considered, when the loop shield length is much greater than the distance from the cable line to the shielding area. For the case of an arbitrary length of the loop shield, I propose a function to approximate the dependence of γ on the ratio of the distance between the extreme points of the loop shield and the shielding area to the distance between the central cable of the power line and the shielding area boundary. To determine the loop shield length, the inverse problem is solved. As a result, I develop recommendations for estimating the loop shield length taking into account the following: the magnetic field reference level in the shielding area; the current in the cable line and the distance between its cables; the amplitude and the phase shift of the current in the loop shield, as well as the distance between its conductors, which are parallel to the cable line; the length of the shielding area and its distance from the cable line.

Loss-tolerant quantum key distribution with mixed signal states

The security of measurement device-independent quantum key distribution (MDI QKD) relies on a thorough characterization of one's optical source output, especially any noise in the state preparation process. Here, we provide an extension of the loss-tolerant protocol [Phys. Rev. A 90, 052314 (2014)], a leading proof technique for analyzing the security of QKD, to MDI QKD protocols that employ mixed signal states. We first reframe the core of the proof technique, noting its generalization to treat $d$-dimensional signal encodings. Concentrating on the qubit signal state case, we find that the mixed states can be interpreted as providing Alice and Bob with a virtual shield system they can employ to reduce Eve's knowledge of the secret key. We then introduce a simple semidefinite programming method for optimizing the virtual operations they can perform on the shield system to yield a higher key rate, along with an example calculation of fundamentally achievable key rates in the case of random polarization modulation error.

Carbonized cellulose microsphere@void@MXene composite films with egg-box structure for electromagnetic interference shielding

Well established internal multilayered structures have been demonstrated to contribute greatly towards outstanding shielding effectiveness (SE) in electromagnetic interference (EMI) shielding systems. A specific encapsulation by intercalating carbonized cellulose microspheres into Ti3C2Tx MXene layers (CCM@MXene) is elaborately designed. The CCM@void@MXene composite films with “egg-box” structure are ultimately achieved by annealing treatment with spherical CCM@MXene as “egg” and Ti3C2Tx MXene layers as “box”. The unique structure with interior void space is attributed to internal multiple reflections of incident electromagnetic waves (EMW) and contributes to the enhancement of EMW absorption. Thanks to the electrically conductive network of Ti3C2Tx MXene adhering to cellulose microspheres surface, the egg-box structure composite films exhibit superb electrical conductivity of 1672.0 ± 7.1 S cm−1 and excellent specific EMI shielding efficiency (up to 18637.14 dB cm2 g−1) at an ultrathin thickness (12.1 ± 0.8 μm). This hierarchical porous egg-box structure offers an ideal potential for application in highly efficient EMI shielding systems.

Neutron background measurement for rare event search experiments in the YangYang underground laboratory

Several experiments have been conducted in the YangYang Underground Laboratory in the Republic of Korea such as the search for dark matter and the search for neutrinoless double beta decay, which require an extremely low background event rate due to the detector system and the environment. In underground experiments, neutrons have been identified as one of the background sources. The neutron flux in the experimental site needs to be determined to design a proper shielding system and for precise background estimation. We measured the neutron spectrum with a Bonner sphere spectrometer, with Helium-3 (3He) proportional counters. The neutron flux at the underground laboratory was so low that the radioactive decays from the radioisotopes contained in the detector created a significant background interference to the neutron measurement. Using Monte Carlo simulations, the intrinsic α background distribution due to the radioactive isotopes in the detector materials, was estimated. The neutron count rate of each Bonner sphere was measured from the pulse height spectrum of the 3He proportional counter, after subtracting the α particle background. The neutron flux and the energy spectrum were determined using the unfolding technique. The total neutron flux measured was (4.46 ± 0.66) × 10−5 cm−2 s−1, and the thermal and fast neutron flux (in the range 1–10 MeV) were (1.44 ± 0.15) × 10−5 cm−2 s−1 and (0.71 ± 0.10) × 10−5 cm−2 s−1, respectively.

Smart MXene-Based Janus films with multi-responsive actuation capability and high electromagnetic interference shielding performances

Smart electromagnetic interference shielding materials with multi-responsive actuation capability are greatly required for next-generation electronics. Here, a flexible, multi-responsive and electrically conductive graphene oxide (GO)/MXene Janus film is fabricated by a scalable sequential vacuum filtration technique. The hydrophilic feature of both GO and MXene enable the formation of Janus-structured films with strong obscure interfaces, achieving multiple stimuli responses (humidity, light, and electricity) and high electromagnetic interference (EMI) shielding performances. The film actuator can be largely bent from −270° to 460° within a wide relative humidity range and exhibits sensitive and fast actuation responses to near-infrared light and electricity. Additionally, the Janus film can also act as the smart switch and soft walking robot. Furthermore, the presence of the highly conductive MXene layer provides the film with attractive EMI shielding effectiveness of 40 dB at a small thickness of 1.5 μm. As a proof-of-concept, a smart EMI shielding curtain and a stimuli-responsive EMI shielding system are assembled using the Janus film. The smart EMI shielding film could effectively tune signal transmission by stimuli to meet specific shielding needs in intelligent electronics and devices.

A high-efficiency liquid hydrogen storage system cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery

Effective thermal insulation technology is served as the key to liquid hydrogen storage. Existing studies have mainly been shedding light on the performance optimization of the passive thermal insulation systems or the direct introduction of refrigerators to achieve zero-boil-off storage. However, considering the immense combustion heat that is taken away by gaseous hydrogen discharged from the passive thermal insulation system, and the additional electric power required to be introduced in driving the refrigerator under the current zero-boil-off system, this paper is intended to propose a novel liquid hydrogen storage system that is cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery. In an effort to reduce the heat leakage, the combustion heat is recovered and converted into electricity, which can then be used to drive the refrigerator in cooling the passive insulation material. In this paper, a thermodynamic calculation model composite of the fuel cell, refrigerator, and passive thermal insulation system was established and verified. According to the results, at a fuel cell efficiency of 50%, the insulation efficiency of the proposed system is improved by up to 80.3% compared with the traditional multi-layer insulation system. Besides, the effects of fuel cell efficiency, refrigerator efficiency, cold shield position, storage pressure, boundary temperature, and system vacuum on the insulation performance were also analyzed.

Development of the models of the magnetic shielding system for ITER neutral beam injectors

The paper is devoted to the development of the models of magnetic shielding system for the ITER neutral beam injectors. As the reactor operation is quasistationary, the magnetic field reduction system of the injectors combines a passive magnetic shield and a set of active correction coils. Due to the strict restrictions on the field inside the injectors, precision computations are required during the design stage. A special attention has been paid to possible gaps between steel panels of the passive magnetic shields due to manufacturing and assembly inaccuracies. A set of models with different levels of detail has been built for the convergence study. It was shown that the mesh needs to have tens of millions finite elements to provide the required computational accuracy.

Intrinsic background radiation of LaBr3(Ce) detector via coincidence measurements and simulations

The LaBr$_3$(Ce) detector has attracted much attention in recent years for its superior characteristics to other scintillating materials in terms of resolution and efficiency. However, it has relatively high intrinsic radiation background due to the naturally occurring radioisotope in lanthanum, actinium and their daughter nuclei. This limits its applications in low counting rate experiments. In this paper, we identified the radioactive isotopes in the $\phi3''\times 3''$ Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation to the experimental spectra to evaluate the activities of the main internal radiation components. % by means of the $\alpha$, $\gamma$ and $\beta$ decays from the $^{138}$La and $^{227}$Ac. The activity of radiation background of B380 is determined to be 1.480 (69) Bq/cm$^3$, the main sources of which include $^{138}$La of 1.425 (59) Bq/cm$^3$, $^{211}$Bi of 0.0136 (15) Bq/cm$^3$, $^{219}$Rn of 0.0125 (17) Bq/cm$^3$, $^{223}$Ra of 0.0127 (14) Bq/cm$^3$, and $^{227}$Th of 0.0158 (22) Bq/cm$^3$.

Prospects for the Development of a Sensitive Atomic Interferometer Based on Cold Rubidium Atoms

An overview of the research results obtained at the All-Russia Research Institute of Physicotechnical and Radio Measurements when creating a fountain type clock is presented. The possibility of using the results obtained for the development of a sensitive atomic interferometer (gravimeter) based on cold rubidium atoms is analyzed. The relevance of the study lies in assessing the prospects for creating an interferometer (gravimeter) based on cold rubidium atoms for absolute measurements of the local value of the gravitational acceleration. The physical principles of operation of an atomic gravimeter are described. A comparison is made between an atomic gravimeter and a fountain-type frequency standard based on cold atoms. The technical solutions required for the creation of an atomic gravimeter with given values of the sensitivity for measuring the acceleration of gravity are proposed. To achieve a gravimeter sensitivity of the order of 1 μGal/Hz1/2, the phase noise of laser radiation, the pressure of residual gases in the vacuum system, and the parameters of the magnetic shield system are estimated.

Simultaneous Ultrafast Transmission and Reflection of Nanometer-Thick Ti3C2Tx MXene Films in the Visible and Near-Infrared: Implications for Energy Storage, Electromagnetic Shielding, and Laser Systems

Unambiguous determination of the optical dynamics in MXenes is necessary for their reliable development into applications such as EMI shielding, energy storage, and laser systems. Here, simultaneou...

A Coil Design and Control Method of Independent Active Shielding System for Leakage Magnetic Field Reduction of Wireless UAV Charger

A Coil Design and Control Method of Independent Active Shielding System for Leakage Magnetic Field Reduction of Wireless UAV Charger

Experiment and numerical investigation of the aero-thermal demise of pristine and pre-damaged GLARE™ fiber-metal laminates

Since many decades researchers have been interrogating the re-entry physics of lunar objects in the Earth’s atmosphere. A request like ‘demise + re-entry’ in a web search engine gives hundreds if not thousands of studies concerned with the breakup and the disappearance of space flotsam in the Earth’s atmosphere. However, it is hard to comprehend a rational reason why the engineering physics involved in the thermal degradation of spacecraft structures still can be explained with inherent uncertainties. Many derelict satellites and spacecraft are orbiting the Earth. They will gradually enter the Earth’s atmosphere attributed to the gravitational force and may will not survive the aero-thermal load induced by the dense Earth’s atmosphere. This study, therefore, investigated the propensity to aero-thermal demise of a pristine and a pre-damaged spacecraft shielding structure during atmospheric re-entry. The shield was made of a GLAss fiber REinforced aluminum panel, which accommodated five quasi-isotropic S2-glass fiber reinforced FM94-epoxy laminates alternately stacked between six aluminum 2024-T3 alloy sheets. The pre-damage of the shielding system was akin to a damage can be generated by an impact of a micrometeoroid. To impart the pre-damage, a GLAss fiber REinforced aluminum plate was first impacted with a 2 mm diameter stainless steel spherical projectile at 5.49 km/s. The projectile perforated through the plate. Next, the perforated GLAss fiber REinforced aluminum plate was exposed to an air plasma-jet (oxygen dissociated) of a specific enthalpy of 5.4 × 103 kJ/kg at standard air pressure conditions. The high enthalpy plasma thermally degraded the pre-damaged plate, while debris was discharged uprange and downrange out of the plate. The dynamic pressure of the plasma flow exacerbated the debris discharge. The endothermic destruction of a pristine GLAss fiber REinforced aluminum specimen followed several steps: first, layer-after-layer oxidation and melting of the aluminum sheets; next, decomposition and sublimation of epoxy accompanied by thermal and viscous diffusion of molten aluminum and molten glass fibers; finally, the onset of a hole in the pristine specimen. By contrast, the plasma-jet that streamed through the punched hole of the pre-damaged GLAss fiber REinforced aluminum specimen, had thermally decomposed the frontal material layers of the specimen to a large extent in the initial few seconds. The punched hole, however, did not succumb to enlarge after the surface temperature of the GLAss fiber REinforced aluminum specimen reached an asymptote. To reproduce the experimental findings, a new Moving Mesh Front procedure had been developed and implemented in a Lagrangian finite element framework. The numerical analysis considered the temperature-dependent thermal properties of orthotropic S2-glass/FM94-epoxy composites and isotropic aluminum alloys. For a comparable heating condition, the agreement between the predicted and the measured temperatures of the specimen front surface was within 4.4%, while the corresponding agreement was within 6.7% for the rear surface temperature of the test specimen.

Monte Carlo dosimetric characterization of a new high dose rate Yb brachytherapy source and independent verification using a multipoint plastic scintillator detector.

A prototype Yb source was developed in combination with a dynamic rotating platinum shield system (AIM-Brachy) to deliver intensity modulated brachytherapy (IMBT). The purpose of this study was to evaluate the dosimetric characteristics of the bare/shielded Yb source using Monte Carlo (MC) simulations and perform an independent dose verification using a dosimetry platform based on a multipoint plastic scintillator detector (mPSD). The TG-43U1 dosimetric parameters were calculated for the source model using RapidBrachyMCTPS. Real-time dose rate measurements were performed in a water tank for both the bare/shielded source using a custom remote afterloader. For each dwell position, the dose rate was independently measured by the three scintillators (BCF-10, BCF-12, and BCF-60). For the bare source, dose rate was measured at distances up to 3cm away from the source over a range of 7cm along the catheter. For the shielded source, measurements were performed with the mPSD placed at 1cm from the source at four different azimuthal angles ( , 9 , 18 , and 27 ). The dosimetric parameters were tabulated for the source model. For the bare source, differences between measured and calculated along-away dose rates were generally below 5-10%. Along the transverse axis, deviations were, on average (range), 3.3% (0.6-6.2%) for BCF-10, 1.7% (0.9-2.9%) for BCF-12, and 2.2% (0.3-4.4%) for BCF-60. The maximum dose rate reduction due to shielding at a radial distance of 1 cm was 88.8±1.2%, compared to 83.5±0.5% as calculated by MC. The dose distribution for the bare/shielded Yb source was independently verified using mPSD with good agreement in regions close to the source. The Yb source coupled with the partial-shielding system is an effective technique to deliver IMBT.

ACTIVE SHIELDING OF EXTERNAL MAGNETIC FIELD OF BUILT-IN TRANSFORMER SUBSTATIONS

This paper deals with the mitigation of low-frequency magnetic field of build-in transformer substations down to the reference level 0.5 μT in nearby living spaces. To meet the reference level, we substantiate the actuality of the usage of active shielding methods having higher efficiency, comparably to metal consuming passive shielding. We show that the optimization of parameters and localization of compensation coils is the main goal of the synthesis of the active shielding system. The solution of synthesis problem is based on the developed 3D numerical model by using particles multiswarm optimization algorithms from Pareto-optimal solutions set taking into account binary preference relations. This allows justifying the usage of simple active shielding system for magnetic field mitigation down to the reference level in living spaces, located near build-in transformer substations (2×400 kVA, 6/0.4 kV). The synthesized active shielding system has two plane compensation coils installed near the ceiling (wall) of the substation room. The area of each coil is less than 10 m2 and the number of ampere-turns is less than 30. We show that the efficiency of the active shielding system is 6 when it electric power consumption is less than 100 W. This allows mitigating the magnetic field down to 0.5 μT in 40 m2 living space located on top or side from the substation. The application of synthesized active shielding system (subject to the positive results of experimental studies of their full-scale physical models) allows solving the actual and socially significant problem of the health protection of tenants of residential buildings with build-in transformer substations from the negative effects of power frequency magnetic field.

Active Shielding of External Magnetic Field of Built-In Transformer Substations

This paper deals with the mitigation of low-frequency magnetic field of build-in transformer substations down to the reference level 0.5 μT in nearby living spaces. To meet the reference level, we substantiate the actuality of the usage of active shielding methods having higher efficiency, comparably to metal consuming passive shielding. We show that the optimization of parameters and localization of compensation coils is the main goal of the synthesis of the active shielding system. The solution of synthesis problem is based on the developed 3D numerical model by using particles multiswarm optimization algorithms from Pareto-optimal solutions set taking into account binary preference relations. This allows justifying the usage of simple active shielding system for magnetic field mitigation down to the reference level in living spaces, located near build-in transformer substations (2×400 kVA, 6/0.4 kV). The synthesized active shielding system has two plane compensation coils installed near the ceiling (wall) of the substation room. The area of each coil is less than 10 m2 and the number of ampere-turns is less than 30. We show that the efficiency of the active shielding system is 6 when it electric power consumption is less than 100 W. This allows mitigating the magnetic field down to 0.5 μT in 40 m2 living space located on top or side from the substation. The application of synthesized active shielding system (subject to the positive results of experimental studies of their full-scale physical models) allows solving the actual and socially significant problem of the health protection of tenants of residential buildings with build-in transformer substations from the negative effects of power frequency magnetic field.