Superior Radiation Research Articles

The comparison of a thin-film ZnO nanodevice with silicon-based electronic devices for diagnostic X-ray beam detection

Radiation detector devices are of fundamental importance for diagnosing diseases and helping to choose the most appropriate medical treatment. Zinc oxide (ZnO) thin films are not usually applied as X-ray photon sensors; however, this study intends to present potential results that enable its application for medical diagnostic use. The damage of the ionizing radiation in typical electronic components (such as transistors) occurs due to the defects generated either in the semiconductor crystal or in the insulating oxide layer, which compromises their long-term use as X-ray detectors. This study also provides some comparisons between the proposed ZnO nanodevice and other semiconductor devices, including photodiode, phototransistor, bipolar junction transistor (BJT), and MOSFET. Based on these comparisons, some advantages and disadvantages of using ZnO thin film will be discussed. Basically, it can be summarized that, although the other semiconductor devices produced a higher intense response, the innovative ZnO thin film-based device presented interesting results that make it promising for radiation detection applications. Furthermore, it has advantages such as superior physical resistance and radiation hardness when compared to ionization chambers and transistor-type devices, respectively.

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals.

Helium bubbles are known to form in nuclear reactor structural components when displacement damage occurs in conjunction with helium exposure and/or transmutation. If left unchecked, bubble production can cause swelling, blistering, and embrittlement, all of which substantially degrade materials and—moreover—diminish mechanical properties. On the mission to produce more robust materials, nanocrystalline (NC) metals show great potential and are postulated to exhibit superior radiation resistance due to their high defect and particle sink densities; however, much is still unknown about the mechanisms of defect evolution in these systems under extreme conditions. Here, the performances of NC nickel (Ni) and iron (Fe) are investigated under helium bombardment via transmission electron microscopy (TEM). Bubble density statistics are measured as a function of grain size in specimens implanted under similar conditions. While the overall trends revealed an increase in bubble density up to saturation in both samples, bubble density in Fe was over 300% greater than in Ni. To interrogate the kinetics of helium diffusion and trapping, a rate theory model is developed that substantiates that helium is more readily captured within grains in helium-vacancy complexes in NC Fe, whereas helium is more prone to traversing the grain matrices and migrating to GBs in NC Ni. Our results suggest that (1) grain boundaries can affect bubble swelling in grain matrices significantly and can have a dominant effect over crystal structure, and (2) an NC-Ni-based material can yield superior resistance to irradiation-induced bubble growth compared to an NC-Fe-based material and exhibits high potential for use in extreme environments where swelling due to He bubble formation is of significant concern.

Superior radiation tolerance via reversible disordering-ordering transition of coherent superlattices.

Materials capable of sustaining high radiation doses at a high temperature are required for next-generation fission and future fusion energy. To date, however, even the most promising structural materials cannot withstand the demanded radiation environment due to irreversible radiation-driven microstructure degradation. Here we report a counterintuitive strategy to achieve exceptionally high radiation tolerance at high temperatures by enabling reversible local disordering-ordering transition of the introduced superlattice nanoprecipitates in metallic materials. As particularly demonstrated in martensitic steel containing a high density of B2-ordered superlattices, no void swelling was detected even after ultrahigh-dose radiation damage at 400-600 °C. The reordering process of the low-misfit superlattices in highly supersaturated matrices occurs through the short-range reshuffling of radiation-induced point defects and excess solutes right after rapid, ballistic disordering. This dynamic process stabilizes the microstructure, continuously promotes in situ defect recombination and efficiently prevents the capillary-driven long-range diffusion process. The strategy can be readily applied into other materials and pave the pathway for developing materials with high radiation tolerance.

A synergistic effect of heavy metal oxides to enhance the physical, optical, and radiation-absorption properties of TeO2-Li2O-BaO glasses

A series of 75TeO2-(20-x)Li2O-xBaO glasses was successfully synthesized using the melt-quenching method. The glass samples were labeled as TLB05, TLB10, TLB15, TLB20 and TLB25 for x = 5, 10, 15, 20 and 25 mol% respectively. The prepared glasses were studied for their structural, optical, and radiation shielding properties. The optical band gap of the glasses decreased linearly from 3.45 to 3.28 eV with BaO in the range 5−25 mol%. The analysis of the thermal properties shows an increase in Tg values with the replacement of Li2O by BaO. The gamma ray shielding coefficients for the glasses estimated by FLUKA simulation and validated by XCOM varied from 0.0329 to 1.4383 cm2g−1, 0.0332 – 1.4879 cm2g−1, 0.0334 – 1.5327 cm2g−1, 0.0335 – 1.5671 cm2g−1, and 0.0336 – 1.5964 cm2g−1 for BaO concentration of 5%, 10%, 15%, 20%, and 25% respectively. Generally, the introduction of BaO improved the photon and charged particles (electron, proton, alpha particle, carbon ions) absorbing parameters of the glasses. The fast neutron removal cross section of the TLB glasses grew from 0.0995 to 0.1014 cm−1 as the molar concentration of BaO declines from 25 to 5 mol%. The increase in the BaO content also quenched the thermal neutron absorption cross section. For TLB5 – TLB25, the coherent, incoherent, absorption, and total thermal neutron cross sections varied between 1.0582 and 1.2059 cm−1, 0.1251 – 0.0024 cm−1, 9.5411 – 0.0876 cm−1, and 10.7244 – 1.2958 cm−1 accordingly. In general, TLB25 displayed the most effective photon shielding ability but the weakest neutron absorber. The TLB glasses in addition showed superior radiation shielding ability compared to some conventional shields.

Lead-free Sb-based polymer composite for γ-ray shielding purposes

Abstract This study ailm was to fabricate and investigate the gamma photon shielding efficiency of antimony (Sb) doped polymer resin composites. The orthophthalic unsaturated polyester resin (C16O7H14) and antimony powder have been used as matrix and filler material, respectively. Gamma radiation shielding capacities of the polymer resin composites doped with 325 mesh sized-antimony particles from 5 to 20 wt% have been investigated. Experimental measurements of the samples have been obtained using an HPGe detector equipped with gamma spectrometer by 241 Am, 133 Ba, 57 Co, 22 Na, 137 Cs, 152 Eu, 54 Mn and 60 Co radioactive point sources varying from 59.5 to 1408.0 keV energies. To explore the gamma-ray attenuation features, linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half value layer (HVL), tenth value layer (TVL), mean free path (MFP), effective atomic number (Zeff), the radiation protection efficiency (RPE) were evaluated. According to the obtained results, it was found that Sb(20%) showed the superior radiation shielding capacity than the other samples. The measured data have been compared with those of WinXCOM, and they were found to be in a good agreement with each other.

Optical and radiation shielding features for some phospho-silicate glasses

Glass composition comprising of SiO2-Na2O-K2O-P2O5 with CaO/BaO were synthesised and characterized using XRD and UV-Vis spectroscopy. The optical features were analysed in terms of band gap (Eg), refractive index (n), molar refraction (RM), molar polarizability (αm), reflection loss (RLOSS), optical transmission (TOptical), metallization criterion (Mcriterion), dielectric constant (εStatic, εOptical), optical electronegativity (χ) and optical basicity (Ʌ). The Eg of glasses acquired using Tauc’s plot and ASF methods authenticates the applicability of both methods as equally good. The Eg value decreases, whereas n increases with an increase in alkaline earth metal oxides (CaO/BaO) content in the glass samples. The Mcriterion exhibits metallic nature of the glasses. The RM and αm decreases as CaO/BaO content increases; whereas RLOSS and TOptical remains constant for the glasses. The dielectric constants increase as CaO/BaO content increases. The photon attenuation parameters were investigated using MC simulations (PHITS and GEANT4) and theoretically using WinXCom. Among all glasses, S8 glass sample has highest μ/ρ, μ, Zeff, Neff and lowest mfp values. Further, S8 glass has low values of both stopping power (SP) and range (ℜp); as required for shielding from charged particles. The slow and fast neutron shielding ability also escalates with an increase in CaO/BaO content in glass matrix. Comparative analysis confirms that S8 glass sample possess superior radiation shielding competency not only for neutral radiations (photon and neutron beams), but also for charged particles (e, p, α and C-ion beams) as compared to several commercial shielding materials.

Effects of TiO2, V2O5, MnO2 and Tl2O3 on structural, physical, optical and ionizing radiation shielding properties of strontium boro-tellurite glass: An experimental study

We investigate the effect of various modifiers (vanadium oxide, manganese oxide, thallium oxide, and titanium oxide) on the structural, optical, and radiation shielding properties of strontium boro-tellurite glass. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and physical properties were employed to investigate the glasses' structure. The diffuse-reflectance spectrum was used to determine band gap and optical parameters. The mass attenuation coefficient (MAC) was measured experimentally, and the obtained results are then benchmarked with the simulated data from XCOM for the same compounds. The experimental results exhibit a reasonable correlation with the XCOM data with relative difference between 0.75% and 5.23%. The Kolmogorov-Smirnov (K–S) test further ascertained from a statistical point of view that the experimentally measured data matched very well the data obtained from the XCOM with the maximum vertical deviation (Dn) between 0.66% and 1.66% in all samples. The XRD proved the amorphous structure for all samples. The FTIR results showed three bands placed at 500–815 cm−1, 815–1150 cm−1, and 1150–1502 cm−1, corresponding to TeO4 and B–O–B, BO4, and BO3, respectively. The sample containing thallium oxide (Tl2O3) showed the highest density (5.1024 g/cm3), then manganese (SBT:Mn, 4.2333 g/cm3), titanium (SBT:Ti, 4.0591 g/cm3), and vanadium (SBT:V, 3.6875). The SBT:Mn and SBT:V samples recorded the highest (3.7180 eV) and the lowest (2.7480 eV) bandgap, respectively. In contrast, the mass attenuation coefficient results ranged from 0.2295 to 0.6479 for SBT:V and SBT:Tl samples, respectively. The values of thickness equivalent for SBT glass samples (Deq) are 16.362, 13.650, 13.052, and 4.188 for SBT:V, SBT:V, SBT:Ti, SBT:Mn, and SBT:Tl, respectively. Based on acquired results, the SBT:Tl sample has superior radiation shielding features that nominate to be a radiation shielding substance.

Effect of fillers on the behaviour of heavy-weight concrete made by iron sand

Heavy-weight concrete refers to the concrete with unit weight ≥ 2600 kg/m3, which is produced using high-density (specific gravity ≥ 3.0) aggregates. It is commonly adopted as the construction material in nuclear power stations and nuclear medicine facilities due to its superior radiation shielding performance. However, the mechanical properties, especially passing ability of heavy-weight concrete reduced significantly since the cement paste is not able to hold the high-density aggregates firmly. To solve this problem, cementitious fillers, such as silica fume (SF) and fly ash (FA) was adopted, which was well-known to be effective in increasing the flowability by improving the wet packing density (WPD) such that more excess water could be produced to lubricate the solid particles. Moreover, the fillers could enhance the segregation resistance by increasing the fine powders content. Therefore, in this paper, a total of 75 heavy-weight concrete mixes with and without SF or FA partially replacing cement were designed and tested for their flowability, segregation resistance, passing ability, unit weight and compressive strength. Results demonstrated that SF could improve the passing ability and WPD simultaneously whereas FA could improve passing ability but not necessarily WPD of heavy-weight concrete. At last, at a given cementitious materials composition, the passing ability could be positively correlated to WPD of heavy-weight concrete.

Track-weighted imaging analysis of white matter microstructures in healthy children: Sex and hemispheric differences.

Structural substrates of sex differences in human function and behavior have been elucidated in previous studies. Diffusion weighted magnetic resonance imaging (DW-MRI) is a widely used non-invasive imaging technique in studying human brain white matter structural organization. While many DW-MRI studies reporting sex differences in WM structure are based on diffusion tensor imaging (DTI) measures, tract specific microstructural differences require further investigation. In this study, we aim to investigate sex differences and sex-specific hemispheric differences in white matter microstructural development in healthy 8-year-old children based on novel track weighted imaging (TWI) analysis. Average pathlength map (APM) is a TWI contrast in which the average length of fibers passing through a voxel is utilized. In this study, we employed tract specific APM measures to evaluate sex differences in WM microstructural development. A total of 37 WM tracts were analyzed including 7 commissural tracts, 9 bilateral association tracts and 6 bilateral projection tracts. APM maps were generated for each tract. Tract-wise group tests were done using the mean values of APM maps. Sex differences were tested using general linear model based group comparisons. Age and total brain volume were included as covariates in the group analysis. Sex specific hemispheric differences were performed for the 15 bilateral tracts. One sample t-tests were done independently for left>right and right>left cases and the APM measures were controlled for age and total cerebral hemispheric volume. P-values<0.05 were considered significant after correcting for multiple comparisons accounting for the total number of tracts. Significant sex differences were revealed in APM measures between boys and girls in 11 WM tracts including rostral body of corpus callosum (CC), left inferior fronto-occipital fasciculus (IFOF), right cingulum, bilateral first and second segments of superior longitudinal fasciculus (SLF), right middle longitudinal fasciculus (MLF), bilateral fronto-pontine (FPT) and right parieto-occipital pontine tracts (POPT). The sex differences showed higher APM values for these 11 tracts in boys as compared to that of girls. In hemispheric differences analysis for both boys and girls, 2 tracts, arcuate fasciculus and optic radiation showed higher APM in left tracts as compared right; 5 tracts, IFOF, MLF, third segment of SLF, FPT and superior thalamic radiation showed higher APM in right tracts as compared to left. This indicates that boys and girls possess similar lateral asymmetries in these 7 tracts. Additionally, anterior thalamic radiation (ATR) showed higher APM in left tract and 4 tracts, first segment of SLF, POPT, inferior longitudinal fasciculus and cortico-spinal tract showed higher APM in right for boys. In girls, second segment of SLF and uncinate fasciculus showed higher APM in right hemisphere. These results indicate different lateral asymmetries between boys and girls for 7 tracts. Overall, boys showed higher average fiber length in most of the tracts, even after controlling for total brain volume.

On the helium bubble swelling in nano-oxide dispersion-strengthened steels

The development of structural materials resistant to harsh radiation environments requires an in-depth understanding of the early stage of the aging processes. In radiation environments with high transmutation helium production rates such as in fusion and spallation applications, even materials with otherwise acceptable radiation stability may suffer from radiation embrittlement related to helium bubble formation. While theoretical modeling of helium-assisted cavity nucleation in pure metals and simple alloys provides some useful guidelines at the atomic scale level, these, however, do not overlap with the size resolution of available experimental techniques. In this study, we employed slow positron beam spectroscopy to characterize the nucleation and growth of nano-scale helium bubbles in martensitic steels strengthened by thermodynamically stable nano-oxide dispersoids. In combination with transmission electron microscopy, we experimentally characterized the evolution of helium bubbles from small clusters of radiation-induced vacancies to large cavities well resolvable by TEM. Superior radiation resistance of oxide-dispersion strengthened steels dominates only in the early stages of bubble evolution, where positron lifetime measurements provide a missing piece of the microstructural puzzle conventionally constructed by TEM.

An integrated forecasting system based on knee-based multi-objective optimization for solar radiation interval forecasting

In the context of global carbon neutrality, solar energy deserves more attention as a clean energy source. Accurate solar radiation forecasting techniques can provide favorable theoretical support for the siting and management of solar power plants. This study aims to establish an integrated interval forecasting system to obtain better solar radiation interval forecasting results. In the proposed system, a feature extraction method based on mutual information is used to reduce the dimension of correlation variables. Then, a dual-channel input structure is constructed with the dimensionally reduced variables and lagged terms of solar radiation. A hybrid kernel relevance vector machine is developed to construct the forecasting intervals of solar radiation. In the hybrid kernel, a newly developed knee-based multi-objective jellyfish search is used to determine the weight of different kernel functions. According to the experiment results based on three American solar sites, it is demonstrated that the proposed system can obtain superior solar radiation forecasting intervals which provide higher interval coverage rate and narrower interval width. Through the optimization of the weight of the kernel function, we can obtain a forecasting interval that is more balanced between the forecasting coverage and the width of the forecasting intervals.

Life After Mild Traumatic Brain Injury: Widespread Structural Brain Changes Associated With Psychological Distress Revealed With Multimodal Magnetic Resonance Imaging

BackgroundTraumatic brain injury (TBI) can alter brain structure and lead to onset of persistent neuropsychological symptoms. This study investigates the relationship between brain injury and psychological distress after mild TBI using multimodal magnetic resonance imaging. MethodsA total of 89 patients with mild TBI from the TRACK-TBI (Transforming Research and Clinical Knowledge in Traumatic Brain Injury) pilot study were included. Subscales of the Brief Symptoms Inventory 18 for depression, anxiety, and somatization were used as outcome measures of psychological distress approximately 6 months after the traumatic event. Glasgow Coma Scale scores were used to evaluate recovery. Magnetic resonance imaging data were acquired within 2 weeks after injury. Perivascular spaces (PVSs) were segmented using an enhanced PVS segmentation method, and the volume fraction was calculated for the whole brain and white matter regions. Cortical thickness and gray matter structures volumes were calculated in FreeSurfer; diffusion imaging indices and multifiber tracts were extracted using the Quantitative Imaging Toolkit. The analysis was performed considering age, sex, intracranial volume, educational attainment, and improvement level upon discharge as covariates. ResultsPVS fractions in the posterior cingulate, fusiform, and postcentral areas were found to be associated with somatization symptoms. Depression, anxiety, and somatization symptoms were associated with the cortical thickness of the frontal-opercularis and occipital pole, putamen and amygdala volumes, and corticospinal tract and superior thalamic radiation. Analyses were also performed on the two hemispheres separately to explore lateralization. ConclusionsThis study shows how PVS, cortical, and microstructural changes can predict the onset of depression, anxiety, and somatization symptoms in patients with mild TBI.

In-situ radiation response of additively manufactured modified Inconel 718 alloys

In this study, a novel alloy of modified Inconel 718 produced by laser powder bed fusion is studied before and after in-situ Kr irradiation up to 3 dpa at 200 and 450 °C. Before irradiation, the microstructure consists of dislocation cells having a misorientation angle less than 5° and with an average size of ~500 nm. There are also second phase particles of MC type carbides, Laves phase and oxides such as Y-O, Y-(Ti)-Al-O. While the microstructure consists of stacking fault tetrahedra, faulted and perfect loops after irradiation at 200 °C, dislocation loops are the primary defects at 450 °C. With increasing dose, the size of the defects remains similar at 200 °C while it increases at 450 °C. This has been attributed to the existence of vacancy type defects at 200 °C and the different defect transport mechanisms at different temperatures. Moreover, matrix and second phase particle compositions seem to be similar after irradiation. The sink strengths of the structures have been calculated and superior radiation resistance of this alloy has been attributed to the existence of fine cell boundaries stabilized by the second phase particles produced by additive manufacturing.

Preparation and Comprehensive Properties of a High-Radiation-Shielding UHPC by Using Magnetite Fine Aggregate.

Nuclear technology benefits humans, but it also produces nuclear radiation that harms human health and the environment. Based on the modified Andreasen and Andersen particle packing model for achieving a densely compacted cementitious matrix, a new magnetite ultra-high-performance concrete (MUHPC) was designed using magnetite fine aggregate as a substitute for river sands with 0%, 20%, 40%, 60%, 80%, and 100% replacement ratios. The comprehensive properties of the developed MUHPC were tested and evaluated. These properties were fluidity, static and dynamic compressive strengths, high-temperature performance, antiradiation behaviors, hydration products, and micropore structures. Experimental results indicate that the developed MUHPC has high work performance and static and dynamic mechanical properties. The gamma ray shielding performance of MUHPC substantially improves with increased magnetite fine aggregate. Corresponding with 100% magnetite fine aggregate substitution, the linear attenuation coefficient of MUHPC is enhanced by 56.8% compared with that of ordinary concrete. Magnetite addition does not change the type of cement hydration products but improves the micropore structures of MUHPC and effectively reduces its total porosity and average pore diameter, thereby contributing to its mechanical and radiation shielding properties. The compressive strength and linear attenuation coefficient of the MUHPC can reach 150 MPa and 0.2 cm−1, respectively. In addition, the MUHPC also exhibits superior mechanical and radiation shielding performance at elevated temperatures (<400 °C). Finally, high strength and antiradiation performance support the use of MUHPC in radiation protection materials in the future.

Structural brain abnormalities in adolescent patients with anorexia nervosa at both the acute and weight-recovered phase.

Previous cross-sectional studies have reported that adolescent patients with anorexia nervosa (AN) showed global gray matter volume (GMV) reductions at the acute phase which were restored at the weight-recovered phase, compared with healthy controls (HC). However, few studies have investigated white matter volume (WMV) or cortical thickness in the context of AN, and results have been inconsistent. Voxel-based morphometry analyses for GM and WM, and cortical thickness analyses for GM were conducted in 31 adolescent patients with AN (vs. 18 HC) in the acute phase, and 16 patients with AN (vs. 13 HC) in the follow-up weight-recovered phase, over an approximately 1-year follow-up interval. At the acute phase, the AN patients showed significant reductions of GMVs and cortical thickness in widespread brain regions, compared with HC. Significant WMV reductions were identified in the bilateral superior longitudinal fascicle, superior thalamic radiation, corona radiata, and fornix, pons, and medulla in the patients. At the weight-recovered phase, the AN patients showed a significant GMV reduction in the left hippocampus, and a WMV reduction in the pons, compared with the HC. There was no difference in cortical thickness between two groups at the weight-recovered phase. In conclusion, the widespread volumetric reductions in GM and WM, and reduced cortical thickness observed in AN patients in the acute phase were not evident in the follow-up weight-recovered phase. The volume reductions observed in the hippocampus and pons in the weight-recovered phase could potentially reflect delayed neurogenesis or recovery from starvation in the AN patients.

Development and characterization of silicon dioxide clad silicon carbide optics for terrestrial and space applications

Silicon carbide (SiC), a non-oxide ceramic with superior thermo-mechanical stability, chemical and radiation resistive properties, finds extensive utilization in optical instruments for terrestrial and space applications. However, its inherent porous texture (α-HCP) becomes a deterrent for high-performance optical telescopes, although several techniques of surface alterations over sintered or reaction-bonded SiC are available. In the present work, the physical vapour deposition (PVD) technique is adopted to deposit a thick (∼5 μm) Silicon dioxide (SiO 2 ) clad layer on a sintered and optically polished SiC (SSiC) substrate. SiO 2 clad layer coated SSiC (SDO-SSiC) substrate reduces the surface porosity of SSiC which is found to be suitable for optical mirror application. Finally, an Al based reflective and oxides protective coatings are deposited on SiO 2 clad layer to achieve reflective behaviour. The surface figure of 75 nm PV (peak-to-valley) and less than 2 nm surface micro-roughness values are achieved which meets the stringent optical telescope specifications for terrestrial and space applications. The structural and nano-mechanical properties of presently developed SiO 2 clad layer-based SiC telescopic mirror have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-Ray Analysis (EDX), atomic force microscopy (AFM), and nanoindentation techniques. The optical properties are investigated by optical profilometry and wavelength based spectrometric (both in visible and infrared ranges) techniques. Finally, space worthiness studies viz., thermo-vacuum, thermal storage, thermal shock and relative humidity tests have been carried out successfully. The process of cleaning, grinding and polishing at each substrate preparation stage and coatings are also reported comprehensively.

Solid-State Welding of the Nanostructured Ferritic Alloy 14YWT Using a Capacitive Discharge Resistance Welding Technique

Joining nanostructured ferritic alloys (NFAs) has proved challenging, as the nano-oxides that provide superior strength, creep resistance, and radiation tolerance at high temperatures tend to agglomerate, redistribute, and coarsen during conventional fusion welding. In this study, capacitive discharge resistance welding (CDRW)—a solid-state variant of resistance welding—was used to join end caps and thin-walled cladding tubes of the NFA 14YWT. The resulting solid-state joints were found to be hermetically sealed and were characterized across the weld region using electron microscopy (macroscopic, microscopic, and nanometer scales) and nanoindentation. Microstructural evolution near the weld line was limited to narrow (~50–200 μm) thermo-mechanically affected zones (TMAZs) and to a reduction in pre-existing component textures. Dispersoid populations (i.e., nano-oxides and larger oxide particles) appeared unchanged by all but the highest energy and power CDRW condition, with this extreme producing only minor nano-oxide coarsening (~2 nm → ~5 nm Ø). Despite a minimal microstructural change, the TMAZs were found to be ~10% softer than the surrounding base material. These findings are considered in terms of past solid-state welding (SSW) efforts—cladding applications and NFA-like materials in particular—and in terms of strengthening mechanisms in NFAs and the potential impacts of localized temperature–strain conditions during SSW.

Radiation tolerance analysis of 4H-SiC PIN diode detectors for neutron irradiation

Silicon carbide (SiC) detector shows sufficient merits for the application of radiation measurement in harsh neutron radiation fields due to the strong radiation tolerance, good environment adaptability, and excellent electrical properties. In order to meet the demand for higher precision measurements, the reliability of SiC detectors under harsh neutron irradiation environments must be characterized. In this work, electrical characteristics, α-particle response, and pulse response speed of 4H-SiC PIN diode detectors were carefully investigated under 1 MeV equivalent neutron irradiation fluence from 5 × 1012 cm−2 to 1 × 1014 cm−2. Before neutron irradiation, SiC detector showed dark current as low as 10 pA at 200 V bias, with superior charge collection efficiency of more than 98%, perfect energy resolution within 0.9%, and ultrafast response speed with a rise time and decay time of 2.1 ns and 5.9 ns, respectively. After a neutron irradiation at fluence of 1 × 1014 cm−2, noticeable changes were found in the forward IV characteristics of SiC detector, but the dark current was stable below 1 nA, with only 5.7% and 0.26% degradation in charge collection efficiency and energy resolution respectively, and the pulse response speed remained unchanged. These results demonstrate 4H-SiC PIN diode detector has superior neutron radiation tolerance, and the obtained evolution characteristics are very valuable for improving the measuring accuracy of SiC detectors in the intense neutron field.

Early life factors and white matter microstructure in children with overweight and obesity: The ActiveBrains project

Exposure to a suboptimal environment during the fetal and early infancy period's results in long-term consequences for brain morphology and function. We investigated the associations of early life factors such as anthropometric neonatal data (i.e., birth length, birth weight and birth head circumference) and breastfeeding practices (i.e., exclusive and any breastfeeding) with white matter (WM) microstructure, and ii) we tested whether WM tracts related to early life factors are associated with academic performance in children with overweight/obesity. 96 overweight/obese children (10.03±1.16 years; 38.7% girls) were included from the ActiveBrains Project. WM microstructure indicators used were fractional anisotropy (FA) and mean diffusivity (MD), derived from Diffusion Tensor Imaging. Academic performance was evaluated with the Battery III Woodcock-Muñoz Tests of Achievement. Regression models were used to examine the associations of the early life factors with tract-specific FA and MD, as well as its association with academic performance. Head circumference at birth was positively associated with FA of the inferior fronto-occipital fasciculus tract (0.441; p=0.005), as well as negatively associated with MD of the cingulate gyrus part of cingulum (-0.470; p=0.006), corticospinal (-0.457; p=0.005) and superior thalamic radiation tract (-0.476; p=0.001). Association of birth weight, birth length and exclusive breastfeeding with WM microstructure did not remain significant after false discovery rate correction. None tract related to birth head circumference was associated with academic performance (all p>0.05). Our results highlighted the importance of the perinatal growth in WM microstructure later in life, although its possible academic implications remain inconclusive.

Proton Radiation Hardness of Perovskite Solar Cells Utilizing a Mesoporous Carbon Electrode

When designing spacefaring vehicles and orbital instrumentation, the onboard systems such as microelectronics and solar cells require shielding to protect them from degradation brought on by collisions with high‐energy particles. Perovskite solar cells (PSCs) have been shown to be much more radiation stable than Si and GaAs devices, while also providing the ability to be fabricated on flexible substrates. However, even PSCs have their limits, with higher fluences being a cause of degradation. Herein, a novel solution utilizing a screen‐printed, mesoporous carbon electrode to act bi‐functionally as an encapsulate and the electrode is presented. It is demonstrated that the carbon electrode PSCs can withstand proton irradiation up to 1 × 1015 protons cm−2 at 150 KeV with negligible losses (&lt;0.07%) in power conversion efficiency. The 12 μm thick electrode acts as efficient shielding for the perovskite embedded in the mesoporous TiO2. Through Raman and photoluminescence spectroscopy, results suggest that the structural properties of the perovskite and carbon remain intact. Simulations of the device structure show that superior radiation protection comes in conjunction with good device performance. This work highlights the potential of using a carbon electrode for future space electronics which is not limited to only solar cells.