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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on PmTh3 by Materials Project

Th3Pm is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Th is bonded to eight equivalent Th and four equivalent Pm atoms to form ThPm4Th8 cuboctahedra that share corners with twelve equivalent ThPm4Th8 cuboctahedra, edges with eight equivalent PmTh12 cuboctahedra, edges with sixteen equivalent ThPm4Th8 cuboctahedra, faces with four equivalent PmTh12 cuboctahedra, and faces with fourteen equivalent ThPm4Th8 cuboctahedra. All Th–Th bond lengths are 3.58 Å. All Th–Pm bond lengths are 3.58 Å. Pm is bonded to twelve equivalent Th atoms to form PmTh12 cuboctahedra that share corners with twelve equivalent PmTh12 cuboctahedra, edges with twenty-four equivalent ThPm4Th8 cuboctahedra, faces with six equivalent PmTh12 cuboctahedra, and faces with twelve equivalent ThPm4Th8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmEr3 by Materials Project

Er3Pm is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Er is bonded to eight equivalent Er and four equivalent Pm atoms to form ErPm4Er8 cuboctahedra that share corners with twelve equivalent ErPm4Er8 cuboctahedra, edges with eight equivalent PmEr12 cuboctahedra, edges with sixteen equivalent ErPm4Er8 cuboctahedra, faces with four equivalent PmEr12 cuboctahedra, and faces with fourteen equivalent ErPm4Er8 cuboctahedra. All Er–Er bond lengths are 3.54 Å. All Er–Pm bond lengths are 3.54 Å. Pm is bonded to twelve equivalent Er atoms to form PmEr12 cuboctahedra that share corners with twelve equivalent PmEr12 cuboctahedra, edges with twenty-four equivalent ErPm4Er8 cuboctahedra, faces with six equivalent PmEr12 cuboctahedra, and faces with twelve equivalent ErPm4Er8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmTm3 by Materials Project

Tm3Pm is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tm is bonded to eight equivalent Tm and four equivalent Pm atoms to form TmPm4Tm8 cuboctahedra that share corners with twelve equivalent TmPm4Tm8 cuboctahedra, edges with eight equivalent PmTm12 cuboctahedra, edges with sixteen equivalent TmPm4Tm8 cuboctahedra, faces with four equivalent PmTm12 cuboctahedra, and faces with fourteen equivalent TmPm4Tm8 cuboctahedra. All Tm–Tm bond lengths are 3.52 Å. All Tm–Pm bond lengths are 3.52 Å. Pm is bonded to twelve equivalent Tm atoms to form PmTm12 cuboctahedra that share corners with twelve equivalent PmTm12 cuboctahedra, edges with twenty-four equivalent TmPm4Tm8 cuboctahedra, faces with six equivalent PmTm12 cuboctahedra, and faces with twelve equivalent TmPm4Tm8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmHo3 by Materials Project

Ho3Pm is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ho is bonded to eight equivalent Ho and four equivalent Pm atoms to form HoPm4Ho8 cuboctahedra that share corners with twelve equivalent HoPm4Ho8 cuboctahedra, edges with eight equivalent PmHo12 cuboctahedra, edges with sixteen equivalent HoPm4Ho8 cuboctahedra, faces with four equivalent PmHo12 cuboctahedra, and faces with fourteen equivalent HoPm4Ho8 cuboctahedra. All Ho–Ho bond lengths are 3.55 Å. All Ho–Pm bond lengths are 3.55 Å. Pm is bonded to twelve equivalent Ho atoms to form PmHo12 cuboctahedra that share corners with twelve equivalent PmHo12 cuboctahedra, edges with twenty-four equivalent HoPm4Ho8 cuboctahedra, faces with six equivalent PmHo12 cuboctahedra, and faces with twelve equivalent HoPm4Ho8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiPmO3 by Materials Project

LiPmO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Li is bonded to six equivalent O atoms to form LiO6 octahedra that share corners with six equivalent LiO6 octahedra and faces with eight equivalent PmO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Li–O bond lengths are 1.87 Å. Pm is bonded to twelve equivalent O atoms to form PmO12 cuboctahedra that share corners with twelve equivalent PmO12 cuboctahedra, faces with six equivalent PmO12 cuboctahedra, and faces with eight equivalent LiO6 octahedra. All Pm–O bond lengths are 2.65 Å. O is bonded in a distorted linear geometry to two equivalent Li and four equivalent Pm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce3Pm by Materials Project

PmCe3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Pm is bonded to twelve equivalent Ce atoms to form PmCe12 cuboctahedra that share corners with twelve equivalent PmCe12 cuboctahedra, edges with twenty-four equivalent CeCe8Pm4 cuboctahedra, faces with six equivalent PmCe12 cuboctahedra, and faces with twelve equivalent CeCe8Pm4 cuboctahedra. All Pm–Ce bond lengths are 3.42 Å. Ce is bonded to four equivalent Pm and eight equivalent Ce atoms to form CeCe8Pm4 cuboctahedra that share corners with twelve equivalent CeCe8Pm4 cuboctahedra, edges with eight equivalent PmCe12 cuboctahedra, edges with sixteen equivalent CeCe8Pm4 cuboctahedra, faces with four equivalent PmCe12 cuboctahedra, and faces with fourteen equivalent CeCe8Pm4 cuboctahedra. All Ce–Ce bond lengths are 3.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmSc3 by Materials Project

PmSc3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pm is bonded to twelve Sc atoms to form PmSc12 cuboctahedra that share corners with four equivalent PmSc12 cuboctahedra, corners with eight equivalent ScPm4Sc8 cuboctahedra, edges with eight equivalent PmSc12 cuboctahedra, edges with sixteen equivalent ScPm4Sc8 cuboctahedra, faces with four equivalent PmSc12 cuboctahedra, and faces with fourteen ScPm4Sc8 cuboctahedra. There are eight shorter (3.35 Å) and four longer (3.38 Å) Pm–Sc bond lengths. There are two inequivalent Sc sites. In the first Sc site, Sc is bonded to four equivalent Pm and eight Sc atoms to form ScPm4Sc8 cuboctahedra that share corners with twelve equivalent ScPm4Sc8 cuboctahedra, edges with eight equivalent PmSc12 cuboctahedra, edges with sixteen ScPm4Sc8 cuboctahedra, faces with four equivalent PmSc12 cuboctahedra, and faces with fourteen ScPm4Sc8 cuboctahedra. There are four shorter (3.35 Å) and four longer (3.38 Å) Sc–Sc bond lengths. In the second Sc site, Sc is bonded to four equivalent Pm and eight equivalent Sc atoms to form ScPm4Sc8 cuboctahedra that share corners with four equivalent ScPm4Sc8 cuboctahedra, corners with eight equivalent PmSc12 cuboctahedra, edges with twenty-four ScPm4Sc8 cuboctahedra, faces with six equivalent PmSc12 cuboctahedra, and faces with twelve ScPm4Sc8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmBeO3 by Materials Project

BePmO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Be is bonded to six equivalent O atoms to form BeO6 octahedra that share corners with six equivalent BeO6 octahedra and faces with eight equivalent PmO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Be–O bond lengths are 1.82 Å. Pm is bonded to twelve equivalent O atoms to form PmO12 cuboctahedra that share corners with twelve equivalent PmO12 cuboctahedra, faces with six equivalent PmO12 cuboctahedra, and faces with eight equivalent BeO6 octahedra. All Pm–O bond lengths are 2.57 Å. O is bonded in a distorted linear geometry to two equivalent Be and four equivalent Pm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

From boundary data to bound states. Part II. Scattering angle to dynamical invariants (with twist)

We recently introduced in [9] a boundary-to-bound dictionary between gravitational scattering data and observables for bound states of non-spinning bodies. In this paper, we elaborate further on this holographic map. We start by deriving the following — remarkably simple — formula relating the periastron advance to the scattering angle: $ΔΦ(J,ε)=χ(J,ε)+χ(-J,ε)$, via analytic continuation in angular momentum and binding energy. Using explicit expressions from [9], we confirm its validity to all orders in the Post-Minkowskian (PM) expansion. Furthermore, we reconstruct the radial action for the bound state directly from the knowledge of the scattering angle. The radial action enables us to write compact expressions for dynamical invariants in terms of the deflection angle to all PM orders, which can also be written as a function of the PM-expanded amplitude. As an example, we reproduce our result in [9] for the periastron advance, and compute the radial and azimuthal frequencies and redshift variable to two-loops. Agreement is found in the overlap between PM and Post-Newtonian (PN) schemes. Last but not least, we initiate the study of our dictionary including spin. We demonstrate that the same relation between deflection angle and periastron advance applies for aligned-spin contributions, with J the (canonical) total angular momentum. Explicit checks are performed to display perfect agreement using state-of-the-art PN results in the literature. Using the map between test- and two-body dynamics, we also compute the periastron advance up to quadratic order in spin, to one-loop and to all orders in velocity. We conclude with a discussion on the generalized ‘impetus formula’ for spinning bodies and black holes as ‘elementary particles’. Our findings here and in [9] imply that the deflection angle already encodes vast amount of physical information for bound orbits, encouraging independent derivations using numerical and/or self-force methodologies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Study of η(1405)/η(1475) in $J/\psi \to \gamma {K}_S^0{K}_S^0{\pi}^0$ decay

Using a sample of (10 . 09 ± 0 . 04) × 10 9 J/ψ decays collected with the BESIII detector, partial wave analyses of the decay $ J/\psi \to \gamma {K}_S^0{K}_S^0{\pi}^0$ are performed within the ${K}_S^0{K}_S^0{\pi}^0$ invariant mass region below 1.6 GeV/ c 2 . The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the ${K}_S^0{K}_S^0{\pi}^0$ invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, i.e., the η (1405) with a mass of $1391.7\pm {0.7}_{-0.3}^{+11.3}$ MeV/ c 2 and a width of $60.8\pm {1.2}_{-12.0}^{+5.5}$ MeV, and the η (1475) with a mass of $1507.6\pm {1.6}_{-32.2}^{+15.5}$ MeV/ c 2 and a width of $115.8\pm {2.4}_{-10.9}^{+14.8}$ MeV. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the ${K}_S^0{K}_S^0{\pi}^0$ invariant mass spectrum deteriorates significantly.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Radiogenic backgrounds in the NEXT double beta decay experiment

Natural radioactivity represents one of the main backgrounds in the search for neutrinoless double beta decay. Within the NEXT physics program, the radioactivity-induced backgrounds are measured with the NEXT-White detector. Data from 37.9 days of low-background operations at the Laboratorio Subterr\'aneo de Canfranc with xenon depleted in $^{136}$Xe are analyzed to derive a total background rate of (0.84$\pm$0.02) mHz above 1000 keV. The comparison of data samples with and without the use of the radon abatement system demonstrates that the contribution of airborne-Rn is negligible. A radiogenic background model is built upon the extensive radiopurity screening campaign conducted by the NEXT Collaboration. A spectral fit to this model yields the specific contributions of $^{60}$Co, $^{40}$K, $^{214}$Bi and $^{208}$Tl to the total background rate, as well as their location in the detector volumes. The results are used to evaluate the impact of the radiogenic backgrounds in the double beta decay analyses, after the application of topological cuts that reduce the total rate to (0.25$\pm$0.01) mHz. Based on the best-fit background model, the NEXT-White median sensitivity to the two-neutrino double beta decay is found to be 3.5$\sigma$ after 1 year of data taking. The background measurement in a Q$_{\beta\beta}\pm$100 keV energy window validates the best-fit background model also for the neutrinoless double beta decay search with NEXT-100. Only one event is found, while the model expectation is (0.75$\pm$0.12) events.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Demonstration of the event identification capabilities of the NEXT-White detector

In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a \TO\ calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of $71.6 \pm 1.5_{\textrm{ stat}} \pm 0.3_{\textrm{ sys}} \%$ for a background acceptance of $20.6 \pm 0.4_{\textrm{ stat}} \pm 0.3_{\textrm{ sys}} \%$ is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Search for direct production of electroweakinos in final states with one lepton, jets and missing transverse momentum in pp collisions at $\sqrt{s} $ = 13 TeV with the ATLAS detector

Searches for electroweak production of wino-like chargino pairs, ${\overset{\sim }{\chi}}_1^{+}{\overset{\sim }{\chi}}_1^{-}$, and of wino-like chargino and next-to-lightest neutralino, ${\overset{\sim }{\chi}}_1^{\pm }{\overset{\sim }{\chi}}_2^0$, are presented. The models explored assume that the charginos decay into a W boson and the lightest neutralino, ${\overset{\sim }{\chi}}_1^{\pm}\to {W}^{\pm }{\overset{\sim }{\chi}}_1^0$. The next-to-lightest neutralinos are degenerate in mass with the chargino and decay to ${\overset{\sim }{\chi}}_1^0$ and either a Z or a Higgs boson, ${\overset{\sim }{\chi}}_2^0\to Z{\overset{\sim }{\chi}}_1^0$ or $h{\overset{\sim }{\chi}}_1^0$. The searches exploit the presence of a single isolated lepton and missing transverse momentum from the W boson decay products and the lightest neutralinos, and the presence of jets from hadronically decaying Z or W bosons or from the Higgs boson decaying into a pair of b-quarks. The searches use 139 fb –1 of $\sqrt{s}$ = 13 TeV proton-proton collisions data collected by the ATLAS detector at the Large Hadron Collider between 2015 and 2018. No deviations from the Standard Model expectations are found, and 95% confidence level exclusion limits are set. Chargino masses ranging from 260 to 520 GeV are excluded for a massless ${\overset{\sim }{\chi}}_1^0$ in chargino pair production models. Degenerate chargino and next-to-lightest neutralino masses ranging from 260 to 420 GeV are excluded for a massless ${\overset{\sim }{\chi}}_1^0$ for ${\overset{\sim }{\chi}}_2^0\to Z{\overset{\sim }{\chi}}_1^0$. For decays through an on-shell Higgs boson and for mass-splitting between ${\overset{\sim }{\chi}}_1^{\pm }/{\overset{\sim }{\chi}}_2^0$ and ${\overset{\sim }{\chi}}_1^0$ as small as the Higgs boson mass, mass limits are improved by up to 40 GeV in the range of 200–260 GeV and 280–470 GeV compared to previous ATLAS constraints.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Potential reductions in fine particulate matter and premature mortality following implementation of air pollution controls on coal-fired power plants in India

Coal-fired power plants (CFPPs) account for > 70% of electricity generation in India, but < 5% of facilities have installed technologies for sulfur dioxide (SO 2 ) and nitrogen oxide (NO X ) removal. Emissions of these pollutants lead to the formation of fine particulate matter (PM 2.5 ) and an increased risk of premature mortality for exposed populations. Here, we use a nested version of the GEOS-Chem global chemical transport model (0.5° × 0.625° resolution) for India to estimate reductions in PM 2.5 concentrations that could have been achieved by implementing existing emission control technologies like flue-gas desulfurization (FGD) and/or selective catalytic reduction (SCR). We quantify the associated burden of disease using the integrated exposure response (IER) and global exposure mortality model (GEMM) functions and compare the costs of premature mortality to those for FGD installation. Model simulations for 2010 suggest installation of FGD would have reduced mean annual PM 2.5 concentrations across India by 8%, compared to 3% with SCR installation, and 11% with both FGD and SCR. A 7–28% reduction in PM 2.5 was simulated for local communities closest to CFPPs (same model grid cell), leading to up to 17% reduction in annual premature mortality. Overall, more than 0.21–0.48 million premature deaths would have been avoided over a 10-year period if FGD had been implemented on all CFPPs, compared to 0.09–0.21 million with SCR and 0.22–0.72 million with both FGD and SCR. Benefits associated with such actions are approximately $\$18.1$–$\$604$ billion USD per year, which is equivalent to ~ 0.44 to 10% of India’s GDP. These results suggest that monetary benefits from avoided premature mortality far outweigh the capital and operational costs of FGD and/or SCR installation of $\$19.5$ billion and/or $\$32.8$ billion per year, respectively. This information is essential because the high costs of installation and operation are often given as reasons for delaying installation and commissioning. Finally, we conclude that policy actions to control air pollution from CFPPs are economically justifiable.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2021

Formin nanoclustering-mediated actin assembly during plant flagellin and DSF signaling

Plants respond to bacterial infection acutely with actin remodeling during plant immune responses. The mechanisms by which bacterial virulence factors (VFs) modulate plant actin polymerization remain enigmatic. Here, we show that plant-type-I formin serves as the molecular sensor for actin remodeling in response to two bacterial VFs: Xanthomonas campestris pv. campestris (Xcc) diffusible signal factor (DSF), and pathogen-associated molecular pattern (PAMP) flagellin in pattern-triggered immunity (PTI). Both VFs regulate actin assembly by tuning the clustering and nucleation activity of formin on the plasma membrane (PM) at the nano-sized scale. By being integrated within the cell-wall-PM-actin cytoskeleton (CW-PM-AC) continuum, the dynamic behavior and function of formins are highly dependent on each scaffold layer’s composition within the CW-PM-AC continuum during both DSF and PTI signaling. Our results reveal a central mechanism for rapid actin remodeling during plant-bacteria interactions, in which bacterial signaling molecules fine tune plant formin nanoclustering in a host mechanical-structure-dependent manner.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Self-reported health impacts of do-it-yourself air cleaner use in a smoke-impacted community

Smoke exposure from wildfires or residential wood burning for heat is a public health problem for many communities. Do-It-Yourself (DIY) portable air cleaners (PACs) are promoted as affordable alternatives to commercial PACs, but evidence of their effect on health outcomes is limited. Pilot test an evaluation of the effect of DIY PAC usage on self-reported symptoms, and investigate barriers and facilitators of PAC use, among members of a tribal community that routinely experiences elevated concentrations of fine particulate matter (PM 2.5 ) from smoke. We conducted studies in Fall 2021 (“wildfire study”; N = 10) and Winter 2022 (“wood stove study”; N = 17). Each study included four sequential one-to-two-week phases: 1) initial, 2) DIY PAC usage ≥8 h/day, 3) commercial PAC usage ≥8 h/day, and 4) air sensor with visual display and optional PAC use. We continuously monitored PAC usage and indoor/outdoor PM 2.5 concentrations in homes. Concluding each phase, we conducted phone surveys about participants’ symptoms, perceptions, and behaviors. We analyzed symptoms associated with PAC usage and conducted an analysis of indoor PM 2.5 concentrations as a mediating pathway using mixed effects multivariate linear regression. We categorized perceptions related to PACs into barriers and facilitators of use. No association was observed between PAC usage and symptoms, and the mediation analysis did not indicate that small observed trends were attributable to changes in indoor PM 2.5 concentrations. Small sample sizes hindered the ability to draw conclusions regarding the presence or absence of causal associations. DIY PAC usage was low; loud operating noise was a barrier to use. This research is novel in studying health effects of DIY PACs during wildfire and wood smoke exposures. Such research is needed to inform public health guidance. Recommendations for future studies on PAC use during smoke exposure include building flexibility of intervention timing into the study design.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Mechanical behavior and shear band of a powder-metallurgy-fabricated CoCrFeMnNi high-entropy alloy during high strain-rate deformation

High-entropy alloys (HEAs) fabricated by powder metallurgy are considered to exhibit extremely-great potential application values in the field for high-speed impact deformation due to their uniform microstructures and compositions. The mechanical behavior of a powder-metallurgy-fabricated (PM) CoCrFeMnNi HEA was investigated at room temperature with strain rates ranging from 1200 s -1 to 2800 s -1 . It was found that the serration behavior and shear localization of the alloy under dynamic conditions occurred. Results also indicated that the serrated flow took place in the PM CoCrFeMnNi HEA during mechanical deformation at high strain rates (>1000 s -1 ) and became more pronounced as the strain rate increased. Furthermore, it was determined that the yield-strength values of the PM CoCrFeMnNi HEA were sensitive to strain rates, where the values increased from 500 MPa to 700 MPa when the strain rates increased from 1200 s -1 to 2800 s -1 . Shear bands with a width of about 20 μm were generated in the PM CoCrFeMnNi HEA after the shear stress reached a maximum value of 635 MPa, which corresponded to a nominal strain of about 8.71. Nanotwins and ultrafine-equiaxed grains with a diameter of about 150 nm also developed at the core of the shear band during deformation. The results revealed that the strength of the shear band was much higher than that of the matrix grain. Nanotwins in the shear band were composed of a single face-centered-cubic (FCC) structure with the twin plane of ($\bar{1}$1$\bar1$), which could be formed via a rotational dynamic recrystallization (RDR).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Radiation induced hardening of beryllium during low temperature He implantation

The effect of ion irradiation on evolution of microstructure and hardening of beryllium with different impurity levels was investigated using TEM and nanoindentation. High purity S-65 grade and less-pure S-200-F grade were implanted by helium ions at temperatures of 50°C and 200°C. 11 different energies were used, so as to create a quasi-homogeneous 3 µm irradiated layer with average radiation damage of 0.1 dpa and average He content of 2000 appm.Nanoindentation experiments demonstrated that before irradiation, the S-200-F and S-65 grades have an average hardness of 3.7$\pm$0.8 GPa and 3.4$\pm$0.8 GPa correspondently. After implantation the hardness of both grades increased by about 60% for the 200°C irradiation and 100% for the 50°C irradiation. The crystallographic analysis of indented grains demonstrated that in the as-received materials the hardness is about 2.5 times higher when the indentation direction is close to the [0001] c-axis of beryllium compared to indentation perpendicular to [0001]. Hardness anisotropy significantly decreased after irradiation: the “soft orientation” was most sensitive to irradiation-induced hardening, with hardness increasing by about 140% after irradiation at 50°C and 100% after irradiation at 200°C, compared to about 15 - 20% for the “hard” orientation at both irradiation temperatures. The higher purity grade had smaller increase of the “soft orientation” hardness: 2.5$\pm$0.3 GPa for the S-65 and 2.9$\pm$0.2 GPa for the S-200-F.At both temperatures in both grades, under TEM investigation the radiation damage appears as “black dots” which are likely to be small dislocation loops with the number density of ~ 10 22 m -3 . No bubbles were observed by TEM inside grains and at grain boundaries. Analysis of the possible hardening contribution demonstrated that the observed “black dots” could be responsible for up to half of the measured hardening, while the rest of the hardening should originate from helium bubbles with the size below the TEM resolution (at or below 1.5 nm).

36 MATERIALS SCIENCE↗