Machining of low percentage beryllium copper alloys
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Habermeyer, J. G.↗
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Results for “beryllium”
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Polishing technique for beryllium mirror
Performance tests, accomplished by inserting entire X ray telescope and polished mirror into vacuum line 67 m long and taking photographs of an X ray resolution source, indicate that polishing increases mirror efficiency from 0.06 percent for X rays at 0.8 nm and increases resolution from 15 to 3.75 arc-seconds.
Froechtenigt, J. F.↗
The isotopic composition of galactic cosmic-ray lithium, beryllium, and boron
The isotopes of cosmic-ray Li, Be, and B near 100 MeV per nucleon have been measured with cosmic-ray telescopes on board the IMP-7 and IMP-8 satellites during 1973 and 1974. The measured isotopic abundances provide a stringent test for models of interstellar propagation and solar modulation. It is found that the isotopic abundances can be explained using a steady-state interstellar propagation model with a 5-g/sq cm leakage mean free path. These results, taken along with Be-10 abundance measurements, indicate a longer lifetime for cosmic rays than that predicted by the usual assumption of an average interstellar density of 1 to 3 atoms per cu cm.
Garcia-Munoz, M.↗
Brazing of beryllium
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Adams, C. M., Jr.↗
A measurement of cosmic-ray beryllium isotopes from 200 to 1500 MeV per nucleon
A balloon-borne superconducting magnetic spectrometer was used in the measurement of cosmic-ray isotopic abundances from lithium through oxygen in the energy range 200-1500 MeV per nucleon. Except for Be-7 all isotopic composition is essentially energy-independent. Be-10 is nearly absent, indicating a mean cosmic-ray age of 6(-3, +10) x 10 to the 6th years. Above about 500 MeV per nucleon, Be-7 drops dramatically in abundance relative to Be-9 and C. By 1500 MeV per nucleon, the relative abundance of Be-7 has become one-half of its lower-energy value. Since Be-7 is the only isotope measured which decays by electron capture, this result is interpreted as indicating that higher-energy Be-7 had an appreciable probability of not being stripped of all its electrons before entering interstellar space where electron pickup is negligible.
Buffington, A.↗
The isotopic composition of galactic cosmic ray lithium, beryllium and boron
The isotopic composition of galactic-cosmic-ray Li, Be, and B has been measured near 100 MeV/nucleon by using the University of Chicago IMP 7 and IMP 8 cosmic-ray telescopes during 1973-1975. The measured abundances allow detailed checks of models of interstellar propagation and solar modulation to be made and conclusions to be drawn concerning the spectral forms at the source and the minimum solar modulation level. For example, comparing these results with local interstellar spectra calculated by using a 'leaky box' model, it is found that if solar modulation is ignored, there is no unique leakage mean free path consistent with all the observations. However, by taking account of a sizable level of residual solar modulation, excellent agreement is obtained between the calculated and measured abundances. Thus, these isotopic abundances confirm the old hypothesis that cosmic-ray Li, Be, and B are produced as secondaries in interstellar space.
Garcia-Munoz, M.↗
The isotopic composition of galactic cosmic-ray beryllium and the cosmic ray age
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Garcia-Munoz, M.↗
Boron and beryllium in Gamma Geminorum
Observations have been made of the B II resonance line at 1362 A in the A0 IV star Gamma Gem with the Princeton spectrometer on the Copernicus satellite at a spectral resolution of 0.05 A. Complementary ground-based observations of the Be II resonance lines at 3130 and 3131 A have been made at Mauna Kea Observatory with a comparable resolution. A model-atmosphere abundance analysis has been done which includes the effects of the lines that blend with the B II and Be II lines. Previous data on Alpha Lyr and Alpha CMa for B II (which blends with a V III feature) have been reanalyzed with the help of new photographic and Reticon data from Mauna Kea which enable the determination of the V abundance. The results show that Gamma Gem is depleted in B by a factor of 5-10 relative to Alpha Lyr and other normal B stars and depleted in Be by at least a factor of four. By comparison, the hot Am star Alpha CMa is B-deficient by about three orders of magnitude and Be-deficient by at least fifteen times. It is suggested that the abundance deficiencies are due to diffusion, and that Alpha CMa is intrinsically a slow rotator, and Gamma Gem is a slightly evolved slow rotator where some, but not all, of the B and Be has resurfaced.
Boesgaard, A. M.↗
High modulus rare earth and beryllium containing silicate glass compositions
Glass compositions having a Young's modulus of at least 16 million psi and a specific modulus of at least 110 million inches consisting essentially of approximately, by weight, 20 to 43% SiO2, 8 to 21% Al2O3, 4 to 10% BeO, 27 to 58% of at least one oxide selected from a first group consisting of Y2O3, La2O3, Nd2O3, Ce2O3, Ce2O3, and the mixed rare earth oxides, and 3 to 12% of at least one oxide selected from a second group consisting of MgO, ZrO2, ZnO and CaO are described. The molar ratio of BeO to the total content of the first group oxides is from 1.0 to 3.0.
Bacon, J. F.↗
The propagation lifetime of galactic cosmic rays determined from the measurement of the beryllium isotopes
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Garcia-Munoz, M.↗
Upper limits for interstellar boron and beryllium abundances toward zeta Ophiuchi
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York, D. G.↗
Beryllium-10 contents of shergottites, nakhlites, and Chassigny
Accelerator mass spectrometry gives the following Be-10 contents (dpm/kg) for the SNC meteorites: Shergotty, 13.0 + or - 1.5 and 17.3 + or - 2.7; Zagami, 18.6 + or - 2.5 and 20.0 + or - 3.2; ALHA 77005, 15 + or - 3; EETA 79001A, 7.8 + or - 1.1 and 6.3 + or - 0.5; EETA 79001B, 8.5 + or - 1.1; Nakhla, 19.7 + or - 3.3; Lafayette, 18.1 + or - 2.5; Governador Valadares, 25.6 + or - 3.6; Chassigny, 20.5 + or - 3.1. The Be-10 contents of the NC meteorites indicate that significant accumulation of cosmogenic nuclides occurred in decimeter rather than planetary-size bodies. The agreement of the He-3, Ne-21, and Be-10 exposure ages of the shergottites also supports small-body irradiation. A long terrestrial age for EETA 79001 appears unlikely.
Pal, D. K.↗
An evaluation of the fatigue crack growth and fracture toughness properties of beryllium-copper alloy CDA172
A series of fracture mechanics tests, using the Be-Cu alloy CDA172 in the round rod product form, was conducted in a lab air environment at room temperature. Tensile data is presented in both the L and C directions and K sub Ic data in both the C-R and C-L orientations. Fracture toughness values were derived from M(T) (center cracked), PS(T) (surface cracked) and CC01 (corner cracked) specimens of varying thickness. Fatigue crack growth data were obtained for the C-R orientation at stress ratio of 0.1, 0.4, and 0.7 and for the C-L orientation at stress ratios of 0.1, 0.3, 0.4, and 0.7.
Forman, Royce G.↗
Hydrogen environment effects on beryllium and titanium aluminides
The NASP program has intensively studied the hydrogen-environment embrittlement (HEE) susceptibility of Be, alpha(2)-Ti3Al, and gamma-TiAl. Tensile tests are being conducted on candidate aerospace structure and propulsion candidate materials from each of the three groups, at temperatures in the -130 to +204 C range, in both 0.1 MPa and 13.8 MPa He and H2 environments, using SEM and TEM to discern the details of environmental effects. It has been established that while alpha(2) Ti3Al is HEE-susceptible even in the room-temperature and 13.8 MPa environment, neither Be nor gamma-TiAl are susceptible, even at the highest temperature tested.
Fritzemeier, L. G.↗
Beryllium 7 and lead 210 in the Western Hemisphere Arctic atmosphere - Observations from three recent aircraft-based sampling programs
Concentrations of the natural radionuclides Be-7 and Pb-210 in the Western Hemisphere Arctic atmosphere were determined during the recent NOAA Arctic Gas and Aerosol Sampling Program (AGASP 3) and NASA Global Tropospheric Experiment/Arctic Boundary Layer Expeditions (GTE/ABLE 3A and ABLE 3B) missions. Be-7 concentrations measured during the AGASP 3 mission north and west of Norway are in accord with previous results for high northern latitudes, but suggest that the 'stratospheric' air masses sampled at the highest elevations reached were significantly diluted with tropospheric air. Higher resolution sampling in the free troposphere of the North American Arctic during ABLE 3B revealed a layer of elevated Be-7 concentrations near 5 km. The distribution of Pb-210 in the high-altitude troposphere of North America during the summer was quite similar to distributions of more frequently measured aerosol species.
Dibb, Jack E.↗
Beryllium and boron constraints on an early Galactic bright phase
The recent observations of Be and B in metal-deficient halo dwarfs are used to constrain a 'bright phase' of enhanced cosmic-ray flux in the early Galaxy. Assuming that this Be and B arises from cosmic-ray spallation in the early Galaxy, limits are placed on the intensity of the early (Population II) cosmic-ray flux relative to the present (Population I) flux. A simple estimate of bounds on the flux ratio is 1 - 40. This upper bound would restrict galaxies like our own from producing neutrino fluxes that would be detectable in any currently proposed detectors. It is found that the relative enhancement of the early flux varies inversely with the relative time of enhancement. It is noted that associated gamma-ray production via pp - pi sup 0 pp may be a significant contribution to the gamma-ray background above 100 MeV.
Fields, Brian D.↗
Primordial nucleosynthesis and the abundances of beryllium and boron
The recently attained ability to make measurements of Be and B as well as to put constraints on Li-6 abundances in metal-poor stars has led to a detailed reexamination of big bang nucleosynthesis in the A is greater than about 6 regime. The nuclear reaction network has been significantly expanded, with many new rates added. It is demonstrated that although a number of A is greater than 7 reaction rates are poorly determined, even with extreme values chosen, the standard homogeneous model is unable to produce significant yields above A = 7, and the (Li-7)/(Li-6) ratio always exceeds 500. We also preliminarily explore inhomogeneous models, such as those inspired by a first-order quark-hadron phase transition, where regions with high neutron/proton ratios can allow some leakage up to A is greater than 7. However, models that fit the A is not greater than 7 abundances still seem to have difficulty in obtaining significant A is greater than 7 yields.
Thomas, David↗
The boron-to-beryllium ratio in halo stars - A signature of cosmic-ray nucleosynthesis in the early Galaxy
We discuss Galactic cosmic-ray (GCR) spallation production of Li, Be, and B in the early Galaxy with particular attention to the uncertainties in the predictions of this model. The observed correlation between the Be abundance and the metallicity in metal-poor Population II stars requires that Be was synthesized in the early Galaxy. We show that the observations and such Population II GCR synthesis of Be are quantitatively consistent with the big bang nucleosynthesis production of Li-7. We find that there is a nearly model independent lower bound to B/Be of about 7 for GCR synthesis. Recent measurements of B/Be about 10 in HD 140283 are in excellent agreement with the predictions of Population II GCR nucleosynthesis. Measurements of the boron abundance in additional metal-poor halo stars is a key diagnostic of the GCR spallation mechanism. We also show that Population II GCR synthesis can produce amounts of Li-6 which may be observed in the hottest halo stars.
Walker, T. P.↗