Shield Design Research Articles

Design and Experiments of a Naturally-Ventilated Radiation Shield for Ground Temperature Measurement

Temperature sensors may produce a measurement error of up to 1 °C because of the influence of solar radiation. In order to obtain a relatively minimal temperature error, a new temperature observation system was proposed in this paper for measuring surface air temperatures. Firstly, a radiation shield was designed with two aluminum plates, eight vents, and a multi-layer structure which is able to resist direct solar radiation, reflected radiation, and upwelling long-ware radiation, as well as ensuring the temperature sensor probe could work effectively. Then, the effect of different solar radiation intensities, wind speeds, scattered radiation intensities, long-wave radiation intensities, and underlying surface reflectivity levels on radiation error was calculated through a computational fluid dynamics (CFD) method. The mapping relationship was established between the various influencing factors and the solar radiation error. A back-propagation (BP) network algorithm was used to fit the discrete data obtained from the simulation to obtain the solar radiation error correction equation. Finally, the solar radiation error correction equation was verified. Outdoor experiments were conducted to confirm this system’s measurement accuracy. According to the experimental findings, the root-mean-square error was only 0.095 °C, which is a relatively high degree by which to reduce the temperature error. In addition, the average difference between the corrected value of the temperature observation system and the reference value was barely 0.084 °C.

Design and fabrication of a biodegradable face shield by using cleaner technologies for the protection of direct splash and airborne pathogens during the COVID-19 pandemic

Due to global supply chain disruptions and high demand for personal protective equipment (PPE), the rapidly expanding COVID-19 crisis left millions of front-line fighters unprotected. The disposal of PPE in the environment caused significant environmental pollution. Hence, indigenous initiatives have been taken to fabricate antiviral and biodegradable face shields with the help of neoteric and cleaner technologies. This paper describes a novel endeavor to design, manufacture, and performance analysis of a face shield made by plastic injection molding and LASER Cutting. Because of the requirement of permanent wear, the face shield's ergonomic design is considered low weight and easy head fixation, alongside high production ability. Here, face shield frames are made with lightweight, biodegradable plastic called Poly Lactic Acid (PLA), whereas an optical grade PLA sheet is used as the visor for better clarity. Visors PLA Sheet is coated with Nano-Silver disinfectant spray to incorporate antiviral properties to the Faceshield. Partially circumferential adjustable elastic straps are used for comfortable head fixation. To evaluate the product, clinical fit tests along with statistical survey were conducted, and the feedback from the end-users on comfort (41% Excellent, 30% Good, 26% Average and 3% Poor), clear view (33% Excellent, 38% Good, 24% Average, and 5% Poor), design features (43% Excellent, 35% Good, and 22% Average), simplicity of installation and disassembly (29% Excellent, 33% Good, and 38% Average), and ease of wearing/removing (45% Excellent, 40% Good, and 15%Average) are encouraging.

Monte Carlo simulation of shielding designs for a cabinet form factor preclinical MV-energy photon FLASH radiotherapy system.

A preclinical MV-energy photon FLASH radiotherapy system is being designed at Stanford and SLAC National Accelerator Laboratory. Because of the higher energy and dose rate compared to conventional kV-energy photon laboratory-scale irradiators, adequate shielding in a stand-alone cabinet form factor is more challenging to achieve. We present a Monte Carlo simulation of multilayered shielding for a compact self-shielding system without the need for a radiation therapyvault. A multilayered shielding approach using multiple alternating layers of high-Z and low-Z materials is applied to the self-shielded cabinet to effectively mitigate the secondary radiation produced and to allow the device to be housed in a Controlled Radiation Area outside of a radiation vault. The multilayered shielding approach takes advantage of the properties of high-Z and low-Z radiation shielding materials such as density, cross-section, atomic number of the shielding elements, and products of radiation interactions within each layer. The Monte Carlo radiation transport code, FLUKA, is used to simulate the total effective dose produced by theoperation. The multilayered shielding designs proposed and simulated produced effective dose rates significantly lower than monolayer designs with the same total material thickness at the regulatory boundary; this is accomplished through the manipulation of the locations where secondary radiation is produced and reactions due to material properties such as neutron back reflection in hydrogen. Borated polyethylene at five weight percent significantly increased the shielding performance as compared to regular polyethylene, with the magnitude of the reduction depending upon the order of the shieldingmaterial. The multilayered shielding provides a path for shielding preclinical FLASH systems that deliver MV-energy bremsstrahlung photons. This approach promises to be more efficient with respect to the shielding material mass and space claim as compared to shielded vaults typically required for clinical radiation therapy with MVphotons. This article is protected by copyright. All rights reserved.

Optical efficiency modulation of vertical alignment liquid crystal displays with transparent shielding and storage electrode

A high-transmittance vertical alignment liquid crystal display (VA-LCD) using a transparent shielding and storage electrode (TSS) design is proposed. The aperture ratio of the proposed four domain TSS pixel with size of 52 × 156 μm improves approximately by 40% over the conventional pixel due to the shielding and storage metal electrode can be replaced by TSS electrode. Experimental results shown that the transmittance of TSS designed panel with 3.2 μm cell gap is 35% higher than that with conventional pixel design, whereas it is only enhanced by 21% when the cell gap is 2.6 μm. The liquid crystal dynamics simulation results revealed that both the effective birefringence and the azimuthally controlled director profile of the liquid crystal layer decreases with TSS pixel design, and these adverse impacts are magnified as the cell gap decreases. This is due to that the introduction of TSS common electrode not only weakens the vertical electric field but also affects the horizontal electric field of liquid crystal layer, which leads to a greater loss of optical efficiency under lower cell gap, resulting in the worse transmittance promotion. The proposed method is expected to be advantageously employed in enhancing transmittance of VA-LCDs for power saving.

An origami shield with supporting frame structures optimized by a feature-driven topology optimization method

In this paper, the design, manufacture and testing of an origami protective shield with a supporting frame structure are presented. It consists of an origami shield surface and a deployable supporting frame structure that needs to be portable and sufficiently stiff. First, for the design of the shield surface, a three-stage origami crease pattern is developed to reduce the shield size in the folded state. The shield surface consists of several stiff modular panels and layered with flexible fabric. The modular panels are made of a multi-layer composite where a ceramic layer is made of small pieces to improve durability as those small pieces enable restriction of crack propagation. Then, the supporting frame structure is designed as a chain-of-bars structure in order to fold into a highly compact state as a bundle of bars and deploy in sequence. Thus, a feature-driven topology structural optimization method preserving component sequence is developed where the inter-dependence of sub-structures is taken into account. A bar with semi-circular ends is used as a basic design feature. The positions of the bar’s end points are treated as design variables and the width of the bars is kept constant. Then, a constraint on the total length of the chain of bars is introduced. Finally, the modular panels made of multi-layer composite and the full-scale prototype of the origami shield are fabricated and tested to verify the bullet-proof performance.

Neutron/Gamma Radial Shielding Design of Main Vessel in a Small Modular Molten Salt Reactor

The SM-MSR (small modular molten salt reactor) has a good prospect for development with regards to combining the superiority of the molten salt reactor and modularization technologies, showing the advantages of safety, reliability, low economic cost and flexibility of site selection. However, because its internal structural parts are not easily replaced, and the outer shielding structure is limited, the lifespan of the reactor vessel and its in-reactor shielding design needs to be addressed. In order to find an optimal shielding model with both high fuel efficiency and strong radiation shielding capability, five different design schemes were proposed in this work, which varied in thickness and boron concentration in inner-shielding materials. The neutron/gamma flux and DPA (displacements per atom)/helium production rates were evaluated to obtain an appropriate scheme. Several beneficial results were obtained. Considering the above factors and the actual manufacturing process, 20 cm-thick boron graphite with a 5 wt% Boron-10 concentration combined with a 1 cm-thick Hastelloy barrel was chosen as the in-reactor shielding structure. Outside the reactor, the neutron flux was reduced to 8.33 × 1010 cm−2 s−1, and the gamma flux was decreased to 1.13 × 1011 cm−2 s−1. The vessel/barrel material could maintain a lifespan of more than 10 years, while the burnup depth was 6.25% lower than that of a model without inner-shielding. The conclusions of this research can provide important references for the shielding design and parameter selections of small molten salt reactors in the future.

An analysis and preliminary experiment of the discharge characteristics of RF ion source with electromagnetic shielding

Combined with two-dimensional (2D) and three-dimensional (3D) finite element analysis and preliminary experimental tests, the effects of size and placement of the electromagnetic shield of the radio-frequency (RF) ion source with two drivers on plasma parameters and RF power transfer efficiency are analyzed. It is found that the same input direction of the current is better for the RF ion source with multiple drivers. The electromagnetic shield (EMS) should be placed symmetrically around the drivers, which is beneficial for the plasma to distribute uniformly and symmetrically in both drivers. Furthermore, the bigger the EMS shield radius is the better generating a higher electron density. These results will be of guiding significance to the design of electromagnetic shielding for RF ion sources with a multi-driver.

Shielding Assessment and Optimization of the Target Station for Medical Isotope Production Based on Superconducting Proton Linac

In response to the worldwide shortage of 99mTc supply caused by the combined consequence from both decommissioning and maintenance of research reactors worldwide, the Institute of Modern Physics (IMP) of the Chinese Academy of Science and Lanzhou University have launched a collaboration to research and develop a 99mTc production solution based on the 25 MeV high-intensity superconducting proton linear accelerator. Radiation from high-current proton bombardment must be evaluated and considered carefully at the design stage to meet radiation protection (RP) policy and requirements of the shielding for the key device. This work employed FLUKA to conduct the shielding assessment of both prompt and residual radiation fields in several iterations, based on a prototype of the high-power target system. The prompt dose rates outside the target station are lower than the institution’s limit. The residual dose rates inside the station fall below 100 μSv/h at 64 h after the end of beam (EOB); the dominant source term is then the target chamber. The service life of the main actuator is expected to be extended by 2.7 times with the current partial shielding design. The simulation accelerating techniques are applied to balance the accuracy of results and the progress of the project at the same time, which is referential to the shielding assessment of large-scale nuclear facilities. The results can also be used in further study and construction of the target station.

Design of a radiation shield applied to surface air temperature monitoring

Due to the solar radiation effect, the current thermometric instruments may produce a radiation error of about 1°C. In this paper, a new radiation shield was designed. Initially, a Computational Fluid Dynamics (CFD) method was employed to create the radiation shield structure. Then, the CFD method was used to quantify the radiation errors of the radiation shield under various environmental conditions. Next, a Multi-layer Perceptron (MLP) network was employed to form a radiation error correction approach for this radiation shield. Finally, the air temperature observation experiments were performed to verify the accuracy of the new radiation shield. A 076B fan aspirated radiation shield was served as an air temperature reference during experiments. The mean absolute error, root mean square error, and correlation coefficient between the radiation error results provided by the correction approach and the measured radiation error results given by the experiments are 0.012°C, 0.015°C, and 0.796°C, respectively.

Simulation Research on Low Frequency Magnetic Radiation Emission of Shipboard Equipment

This paper first introduces the structure of a shipboard equipment control cabinet and the preliminary design of electromagnetic shielding, then introduces the principle of low-frequency magnetic field shielding, and uses silicon steel sheet to shield the low-frequency magnetic field of shipboard equipment control equipment. Based on ANSYS Maxwell simulation software, the low-frequency magnetic field radiation emission of the equipment's conducted harmonic peak frequency point is simulated. Finally, according to MIL-STD-461G test standard, the low-frequency magnetic field radiation emission test is carried out, which meets the limit requirements of the standard. The low-frequency magnetic field shielding technology has practical value. The low-frequency magnetic field radiation emission simulation based on ANSYS Maxwell proposed in this paper is a useful attempt for the quantitative simulation of radiation emission.

The atmospheric X-ray imaging spectrometer (AXIS) instrument: Quantifying energetic particle precipitation through bremsstrahlung X-ray imaging.

The Atmospheric X-ray Imaging Spectrometer (AXIS) described in this work is a compact, wide field-of-view, hard x-ray imager. The AXIS instrument will fly onboard the Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) 6U CubeSat mission and will measure bremsstrahlung x-ray photons in the 50-240keV range with cadmium-zinc-telluride (CZT) detectors using coded aperture optics. AXIS will measure photons generated by energetic particle precipitation for the purpose of determining the spatial scales of precipitation and estimating electron precipitation characteristics. This paper describes the design and testing of the AXIS instrument, including a summary of simulations performed that motivate the shielding, optics, and mechanical design. Testing and characterization is reported that validates the instrument design and shows that the instrument design meets or exceeds the measurement requirements necessary for AEPEX mission success.

Multi-objective optimal design of high-efficient EMI shielding in porous graphene-reinforced nanocomposites

Multi-objective optimal design of high-efficient EMI shielding in porous graphene-reinforced nanocomposites

Determination of linear attenuation coefficient of aggregate serpentine concrete exposed to gamma and neutron radioactive sources

This research was designed to perform linear attenuation calculations for ordinary concrete both through simulation and experiment. The linear attenuation coefficient is an essential parameter for radiation shielding design for both source transport casks and storage bunkers. The shielding properties of concrete designed with Serpentine aggregates of different granule sizes were investigated. The simulation was performed using Radpro computer Software while the experiment involved sourcing for local Serpentine rock, crushing into four different granule sizes of 5 mm, 10 mm, 15 mm and 20 mm respectively and casting the concrete samples, exposure of the samples to gamma and neutron radioactive sources and monitoring with a radiation survey meter, sample weight measurements and concrete sample crushing using a load testing machine for determination of the concrete compressive strength. The results of the linear attenuation calculations showed that there was high consistency in the values obtained by simulation with those obtained via experiment. Very high linear attenuation property was observed when the serpentine concrete samples were exposed to a neutron source, which corroborates the fact that Serpentine rock is a Boron-rich mineral and Boron is known to have high neutron absorption property. The experimentally determined linear attenuation coefficients showed that the values at 15 mm aggregate sizes were higher than those at 5 mm, 10 mm and 15 mm sizes respectively, which demonstrates that better shielding optimization, will be obtained when the concrete cask is fabricated with 15 mm aggregate size.

Monte Carlo simulation of background components in low level Germanium spectrometry

This proceeding presents the decomposition of the background spectra of the four screening detectors GeMPI 1 - 4 at the Gran Sasso Underground Laboratory (LNGS) using Monte Carlo simulations in the Geant4-based framework MaGe. A detailed understanding of the composition of the background spectra was achieved, allowing for the proposal of two new shield designs for future GeMPI-like detectors and enabling a reduction of the integrated background count rate to 15 counts/d/kg in the interval [40, 2700] keV.

Decay heat in ISIS spallation target: simulations and measurements

Spallation targets for neutron production with high energy protons are made of high density and high atomic number materials in order to maximise the yield of neutrons for all the instruments around. Operating a proton beam onto a spallation target produces residual radioactive nuclei either as direct product of the spallation process and as secondary low energy neutron absorption. A reliable estimation of the overall activation and decay heat, as a function of the cooling time and irradiation profile history, is fundamental for a valuable design of the radiation shielding and cooling system during the operation phase as well for envisaging the optimal storage solution at the end of life of the target. This work presents the comparison between the FLUKA predictions of the decay heat in the ISIS TS1 target operated between 2014 and 2019 and the decay heat estimations derived from the measurement of the temperature in each plate at different cooling times. The agreement between the FLUKA predictions and the experimentally assessed values shows and quantifies the goodness of the FLUKA model in predicting measurable physical quantities relevant for the engineering thermal design of the target/reflector and moderator (TRAM) assembly. In addition, it also provides an indirect evidence of the accuracy of the simulated spallation physics and neutron transport throughout the TRAM assembly. Finally this work attempts to highlight and propose a general empirical procedure that could be eventually applied and used to proficiently measure the decay heat at whatever cooling time in targets with similar ISIS design.

Magnetic Behavior of a Laser Deposited Fe–Ni–Mo Alloy

Magnetic shielding in spacecraft is a mission‐critical issue that must be addressed in a timely and effective manner. The high permeability of Fe–Ni–Mo alloys, makes them excellent candidates for magnetic shielding. This article explores a new and innovative approach, enabled by additive manufacturing (AM), to design, build, and test geometrically complex magnetic shields. A Fe–79.7Ni–4.1Mo alloy is additively manufactured using blown powder laser‐directed energy deposition (DED). AM build conditions are explored in the production of magnetic test rings and magnetic shield prototypes. Magnetic hysteresis test data are obtained, allowing for the determination of magnetic permeability, saturation, and coercivity. Detailed microstructural characterization is carried out. Three different prototype shield designs are printed and magnetic shield attenuation data is obtained. The magnetic field attenuation (shield effectiveness) obtained for the AM components is comparable to wrought equivalents. The values reported here for the magnetic permeability are the highest, and that for the magnetic coercivity the lowest, for any blown powder DED‐printed material currently known. The magnetic behavior is discussed with regard to grain size and orientation, as well as grain boundary effects, with all of these attributes contributing to the ultimate performance.

Experimental research on a 50 mK multi-stage adiabatic demagnetization refrigerator

<sec>With the development of condensed matter physics, space observation, and quantum technology in recent years, the demand for ultra-low temperature refrigeration has increased. The adiabatic demagnetization refrigerator (ADR) has the advantages of being unaffected by gravity, compact structure, and relatively low cost, which can meet the needs of space and ground applications.</sec><sec>In this paper, a 50 mK multi-stage ADR is designed and developed which comprises a GM-type pulse tube cryocooler for precooling and three ADR stages connected in series. For easy installation and maintenance, the three ADR stages are placed on a separate cold plate which is connected to the 4 K cold plate via copper columns. The Dy<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub> (GGG) is employed as the refrigerant in the first stage, whereas CrK(SO<sub>4</sub>)<sub>2</sub> · 12H<sub>2</sub>O (CPA) is utilized for the second stage and third stage. To control heat transfer between stages and the 4 K heat sink, active gas-gap heat switch and passive gas-gap heat switch are developed, with the latter having a switching ratio over 1000.</sec><sec>The 4 T, 2 T and 1 T superconducting magnets are utilized in the 1st, 2nd and 3rd stage, respectively, and a numerical model is used to optimize the design of magnetic shielding. In addition, an ADR simulation model with a proportional-integral-derivative (PID) controller is constructed to assist in tuning the controller parameters in the experiment. The lowest temperature achieved in the experiment is 38 mK, with a temperature fluctuation of 10.6 μK. The durations of different cooling power (1, 2 and 3 μW) at 100 mK are also measured. It is calculated that the no-load maintenance time is about 4.3 h, the leakage heat power is about 4.5 μW, and the total cooling capacity is about 71 mJ. This refrigerator is the first Chinese multi-stage ADR that can reach a temperature under 50 mK, which lays an important foundation for subsequent research on continuous adiabatic demagnetization refrigeration.</sec>

Design of Cold Shield in Infrared Detector

Design of Cold Shield in Infrared Detector

Finite element analysis of zero magnetic field shielding for polarized neutron scattering

<sec>Polarized neutron scattering, as one of the experimental techniques of neutron scattering, is a powerful tool for exploring the microstructure of matter. In polarized neutron scattering experiments, magnetic field maintains and guides the neutron polarization, and determines the sample magnetic environment. For complex magnetic sample, it is often necessary to apply zero-field environment at the sample position, so that general polarization analysis becomes feasible. To achieve effective zero-field environment for polarized neutron experiment, carefully designed magnetic field is required.</sec><sec>In this work, we demonstrate a zero-field sample chamber designed for polarized neutron experiment by utilizing both permalloy material and high-<i>T</i><sub>C</sub> superconducting films. This design adopts a simple and low-maintenance ‘deep-well’ shape to achieve effective shielding. The study uses finite element simulation method to analyze the effect of dimensions on the magnetic field shielding performance of the device of the model, including height, arm length, opening radius, and superconductor distance. At optimal dimensions, the designed zero field chamber achieves an internal magnetic field integral of 0.67 G·cm along the neutron path under the geomagnetic field condition. The maximum neutron depolarization for 0.4 nm neutrons is 0.76%, which sufficient for general polarization analysis application. The finite element method simulation results are examined by neutron Bloch equation dynamics simulations and in-lab measurement . Based on the established effective zero-field shielding design, we further discuss the relationship between magnetic field shielding and the dimensions of the device. The application of the device to spectrometers and the future improvement in the device structure are also discussed.</sec>

Radiation shielding design and development of Bi/Ta/PU lead-free flexible textile composites

Aiming at the difficulty of designing flexible shielding materials for lightweight and complex structures, the radiation shielding simulation model of coated fabric was established by SuperMC nuclear simulation software system and the γ-ray shielding performance of the material was predicted. Pb and Ta doped Bi/PU coated fabric composites were prepared by coating process. SEM, EDS, γ-ray shielding performance, mechanical properties, and wear resistance were tested. The results show that the simulated values of shielding performance are in good agreement with the measured values, the maximum deviation of the predicted value is 2.94% and the minimum is 0.25%. Doping Pb and Ta can increase the probability of the photoelectric effect and improve the γ-ray shielding performance of the material. When the doping amount of Ta is 5wt%, the shielding rate (simulation value) of Bi/Ta/PU coated fabric composites to 59.5 keV, 122 keV, and 184 keV γ-rays reaches 29.80%, 20.35%, and 8.09%, respectively, which is 3.13%, 2.32%, and 0.95% higher than that without doping. However, Ta is more environmentally safe and can replace Pb as a shielding additive. Doping auxiliary functional particles will improve the shielding performance but will reduce the material’s wear resistance and mechanical properties. After doping 5%Ta, the wear resistance index decreased by 6.81, and the tensile strength decreased by 4.5 MPa. The influence mechanism of process parameters on shielding performance is further revealed by visual analysis, which provides a new reference for the design of lead-free flexible shielding materials.