Beryllium Data Research Articles

Implications of lithium to oxygen AMS-02 spectra on our understanding of cosmic-ray diffusion

We analyze recent AMS-02 comic-ray measurements of Lithium, Beryllium, Boron, Carbon, Nitrogen and Oxygen. The emphasis of the analysis is on systematic uncertainties related to propagation and nuclear cross sections. To investigate the uncertainties in the propagation scenario, we consider five different frameworks, differing with respect to the inclusion of a diffusion break at a few GV, the presence of reacceleration, and the presence of a break in the injection spectra of primaries. For each framework we fit the diffusion equations of cosmic rays and explore the parameter space with Monte Carlo methods. At the same time, the impact of the uncertainties in the nuclear production cross sections of secondaries is explicitly considered and included in the fit through the use of nuisance parameters. We find that all the considered frameworks are able to provide a good fit. In particular, two competing scenarios, one including a break in diffusion but no reacceleration and the other with reacceleration but no break in diffusion are both allowed. The inclusion of cross-section uncertainties is, however, crucial, to this result. Thus, at the moment, these uncertainties represent a fundamental systematic preventing a deeper understanding of the properties of CR propagation. We find, nonetheless, that the slope of diffusion at intermediate rigidities is robustly constrained in the range $\delta\simeq0.45-0.5$ in models without convection, or $\delta\simeq0.4-0.5$ if convection is included in the fit. Furthermore, we find that the use of the AMS-02 Beryllium data provides a lower limit on the vertical size of the Galactic propagation halo of $z_\mathrm{h}\gtrsim3$ kpc.

AMS-02 beryllium data and its implication for cosmic ray transport

The flux of unstable secondary cosmic ray nuclei, produced by spallation processes in the interstellar medium, can be used to constrain the residence time of cosmic rays inside the Galaxy. Among them, $^{10}$Be is especially useful because of its relatively long half-life of 1.39 Myr. In the framework of the diffusive halo model we describe cosmic ray transport taking into account all relevant interaction channels and accounting for the decay of unstable secondary nuclei. We then compare our results with the data collected by the Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station for the flux ratios Be/C, B/C, Be/O, B/O, C/O and Be/B as well as C, N and O absolute fluxes. These measurements, and especially the Be/B ratio, allow us to single out the flux of $^{10}$Be and infer a best fit propagation time of CRs in the Galaxy. Our results show that, if the cross sections for the production of secondary elements through spallation are taken at face value, AMS-02 measurements are compatible with the standard picture based on CR diffusion in a halo of size $H \gtrsim 5$ kpc. Taking into account the uncertainties in the cross sections, this conclusion becomes less reliable, although still compatible with the standard picture. Implications of our findings for alternative models of CR transport are discussed.

Assessment of beryllium and molybdenum nuclear data files with the RPI neutron scattering system in the energy region from 0.5 to 20 MeV

A series of neutron scattering benchmark measurements were performed on beryllium and molybdenum with the Rensselaer Polytechnic Institute's Neutron Scattering System. The pulsed neutron source was produced by the Rensselaer Polytechnic Institute's Linear Accelerator and a well collimated neutron beam was incident onto the samples located at a distance of 30.07 m. Neutrons that scattered from the sample were measured using the time-of-flight by eight EJ-301 liquid scintillator detectors positioned 0.5 m from the sample of interest. A total of eight experiments were performed with two sample thicknesses each, measured by detectors placed at two sets of angles. All data were processed using pulse shape analysis that separated the neutron and gamma ray events and included a gamma misclassification correction to account for erroneously identified gamma rays. A detailed model of the neutron scattering system simulated each experiment with several current evaluated nuclear data libraries and their predecessors. Results for each evaluation were compared to the experimental data using a figure-of-merit. The neutron scattering system has been used as a means to quantify a library's performance.

What does the PAMELA antiproton spectrum tell us about dark matter?

Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. Depending on the assumptions made regarding cosmic ray propagation in the Galaxy, such constraints can be quite stringent. We revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. We derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. We also note (as have several previous groups) that simple GALPROP-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with PAMELA's observations above ∼ 5 GeV, but that significantly underpredict the flux at lower energies. Although the complexity of modeling cosmic ray propagation at GeV-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. Suggestively, we find that this excess is best fit for mDM ∼ 35 GeV and σ v ∼ 10−26 cm3/s (to bb̄), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the Galactic Center.

Benchmarking of ENDF/B-VII.1 and JENDL-4.0 in the Fast Neutron Range

The author has been able to process ENDF/B-VII.1 using NJOY.99 to produce groupwise data and run a significant number of benchmark cases without issue. Two validation metrics have been calculated to aid comparison of the ENDF/B-VII.1 data with its predecessor ENDF/B-VII.0 and JENDL-4.0. All three datasets show good agreement with benchmark k-effectives however the work suggests possible issues with Beryllium data.

Analysis of the KANT experiment on beryllium using TRIPOLI-4 Monte Carlo code

Beryllium is an important material in fusion technology for multiplying neutrons in blankets. However, beryllium nuclear data are differently presented in modern nuclear data evaluations. Recent investigations with the TRIPOLI-4 Monte Carlo simulation of the tritium breeding ratio (TBR) demonstrated that beryllium reaction data are the main source of the calculation uncertainties between ENDF/B-VII.0 and JEFF-3.1. To clarify the calculation uncertainties from data libraries on beryllium, in this study TRIPOLI-4 calculations of the Karlsruhe Neutron Transmission (KANT) experiment have been performed by using ENDF/B-VII.0 and new JEFF-3.1.1 data libraries. The KANT Experiment on beryllium has been used to validate neutron transport codes and nuclear data libraries. An elaborated KANT experiment benchmark has been compiled and published in the NEA/SINBAD database and it has been used as reference in the present work. The neutron multiplication in bulk beryllium assemblies was considered with a central D–T neutron source. Neutron leakage spectra through the 5, 10, and 17 cm thick spherical beryllium shells were calculated and five-group partial leakage multiplications were reported and discussed. In general, improved C/ E ratios on neutron leakage multiplications have been obtained. Both ENDF/B-VII.0 and JEFF-3.1.1 beryllium data libraries of TRIPOLI-4 are acceptable now for fusion neutronics calculations.

Cosmogenic isotopes and their role in present-day solar paleoastrophysics

Present-day data on 14C and 10Be concentration in natural archives have been statistically analyzed. It has been established that it is difficult to extract information about solar activity variations on long (several Myr and longer) and, especially, short (to 30 years) time scales using radiocarbon data. It has been indicated that beryllium series bear reliable information about short-term, secular, and, probably, 1000-year variations in solar activity. Moreover, 10Be concentration in polar ice can also be used to study the internal dynamics of solar activity. It has been concluded that beryllium data are more promising than radiocarbon ones from the viewpoint of solar paleoastrophysics.

Astronomy: Beryllium data confirm stars' age

Science NewsVolume 166, Issue 12 p. 189-189 Of Note Astronomy: Beryllium data confirm stars' age First published: 02 July 2009 https://doi.org/10.1002/scin.5591661212AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume166, Issue1218 September 2004Pages 189-189 RelatedInformation

Beryllium sensitization, chronic beryllium disease, and exposures at a beryllium mining and extraction facility.

In this study, we examine beryllium sensitization, chronic beryllium disease (CBD), and workplace exposures at a beryllium mining (mine) and extraction facility (mill) in Delta, Utah. Historical airborne beryllium data collected between 1970-1999 included general area (GA), breathing zone (BZ), and personal lapel (LP) measurements and calculations of job-specific quarterly daily-weighted averages (DWVAs). We compared GA, BZ, and DWA data to airborne beryllium data from a mixed beryllium products facility and a beryllium ceramics facility located in Elmore, Ohio and Tucson, Arizona, respectively. At the Delta facility, jobs involving beryllium hydrolysis and wet-grinding activities had the highest air concentrations; annual median GA concentrations were less than 0.3 microg/m3 or both areas. Annual median GA sample concentrations ranged from 0.1-0.4 microg/m(-3) at Delta. These levels were generally lower than Elmore (0.1-1.0 microg/m3) and were comparable to the Tucson facility (0.1-0.4 microg/m3). Median BZ concentrations were higher, whereas DWAs were lower at the Delta facility than at the other two facilities. Among the 87 employees at the Delta facility, 75 participated in the medical survey; there were three persons sensitized, one with CBD. The individual with CBD previously worked at the Elmore facility for 10 years. Cumulative CBD incidence rates were significantly lower at the Delta facility: 0.3 percent compared to 2.0 percent for Elmore and 2.5 percent for the Tucson facility. Sensitization and CBD prevalence rates determined from cross-sectional surveys for the Delta facility were lower than but not significantly different from rates at the other two facilities. There was no sensitization or CBD among those who worked only at the mine where the only exposure to beryllium results from working with bertrandite ore. Although these results are derived from a small sample, this study suggests that the form of beryllium may affect the likelihood of developing CBD. Specifically, exposure to beryl and bertrandite ore dusts or to beryllium salts, in the absence of exposure to beryllium oxide particulates appears to pose a lower risk for developing CBD.

Absolute Equation-of-State Data in the 10–40 Mbar (1–4 TPa) Regime

A technique has been developed that allows the measurement of equations of state of low-atomic-number materials in regimes of extremely high pressure. Using this technique we have obtained absolute multimegabar measurements on the principal Hugoniots of low- $Z$ solids, including data on polystyrene up to 40 Mbar (60 times the previous absolutely measured pressure) and beryllium at pressures up to 15 Mbar. The polystyrene data were able to differentiate between existing theoretical models. The beryllium data confirm theoretical Hugoniots of several materials as high as 65 Mbar.

Benchmark analyses of the ENDF/B-VI, EFF-1 and EFF-2 beryllium data evaluations for neutron transport calculations

Abstract The beryllium data evaluations by Perkins et al. (ENDF/B-VI), Field et al. (EFF-2) and Young and Stewart (EFF-1) are analysed with regard to their use in neutron fusion applications. There are considerable differences in the secondary energy and angle distributions with a strong impact on the neutron transport in beryllium. For EFF-2 and ENDF/B-VI data there are severe discrepancies with measured double-differential cross-sections at several energies and angles. A preference for the EFF-1 beryllium data can be deduced from the analysis of transmission experiments on spherical beryllium assemblies with measurements of the neutron leakage spectra. Owing to compensation effects the calculated neutron multiplication factors of beryllium are not very sensitive to the different beryllium data evaluations.

Analyses of 14 MeV neutron transport in beryllium

The 14 MeVneutron transport in beryllium is analyzed on the basis of an S N -transport procedure with rigorous treatment of the neutron scattering and double-differential cross-sections (DDX-data) from the nuclear data files ENDF/B-VI and EFF-1 (European Fusion File). The latter one uses the Los Alamos (LANL) data evaluation for the beryllium cross-sections. Comparisons with conventional S N P l transport calculations in one- and two-dimensional geometry show that their quality depends on the way of representing and processing the DDX-data on the files. If the DDX-data are given in the Legendre approximation (EFF-1 file) rigorous S N and approximative S N P l transport calculations agree perfectly. If the DDX data are given in the more appropriate angular representation (ENDF/B-VI file), enabling the DDX data processing without making any use of the Legendre approximation, rigorous S N and approximative S N P l calculations disagree significantly. Calculations of integral beryllium experiments show that it is not possible at present to draw a final conclusion on the quality of the EFF-1 and ENDF/B-VI beryllium date evaluations although they show remarkable differences. There are, however, indications that the 14 MeV (n, 2n) cross-section in ENDF/B-VI is too low and that the secondary-energy distribution of the EFF-1 neutron emission cross-section at low secondary energies is too high. Further integral experiments, especially measurements of neutron leakage spectra, are needed for a reliable assessment of the quality of the beryllium data evaluations.

One-boson-exchange approach to dilepton production in nucleon-nucleon collisions

We calculate energy-dependent nucleon-nucleon elastic eross sections and electron-positron pair production differential cross sections for the processes pp→pp, np→np, and pp→ppe +e − , np→npe +e − at laboratory kinetic energies in the 1–5 GeV range. These calculations will be based on a one-boson-exchange (π, ϱ, ω, σ, δ, η) approximation to the nucleonnucleon scattering problem. Strong form factors are included in a manner which preserves gauge invariance. We find excellent results as compared with data for the total elastic cross sections. The calculated differential elastic cross sections show only qualitative agreement with data. For dilepton production in n− p scattering the model overestimates the number of pairs as compared with proton on beryllium data. For the p− p case we find the tensor coupling of the ϱ to the nucleons to be clearly dominant. Data do not yet exist for the p- p case at these energies: we predict them.

Comparative Analysis For Phase IIA and IIB Experiments of the U.S./JAERI Collaborative Program on Fusion Blanket Neutronics

Several fusion-oriented integral experiments were performed in Phase II of the U.S./JAERI Collaborative Program on Fusion Neutronics where the geometrical configurations and source condition closely simulate the incident spectrum in fusion reactors. The main objective of the program is to estimate the uncertainties involved in predicting tritium breeding rate in Li/sub 2/O and other neutronics parameters in fusion blanket that include engineering features (i.e., first wall, multiplier). In Phase II, the Li/sub 2/O test assembly is placed in one end of a Li/sub 2/CO/sub 3/ enclosure that houses the D-T neutron source. Predicted local and integrated tritium production rates (TPR) from /sup 6/Li (T/sub 6/), /sup 7/Li (T/sub 7/) and natural lithium (T/sub N/) were compared to measurements in various configurations that included reference, first wall and beryllium multiplier experiments (Phase IIA) in addition to repeating these experiments with a FW/Be layer covering the interior surface of the Li/sub 2/CO/sub 3/ enclosure (Phase IIB). Other neutronics parameters that included source characterization by foil measurements, in-system reaction rates, and in-system spectrum measurements were also analyzed. The analyses were carried out independently by both parties using various 3-D Monte Carlo codes and 2-D discrete ordinates codes and data libraries. The results ofmore » the analyses are reported in this paper with emphasis placed on the impact of the beryllium data on the discrepancies found between predictions and measurements.« less

Beryllium in four NIMROC reference samples

Beryllium data are presented for four standard reference samples, all of igneous origin, that were prepared by the National Institute for Metallurgy (Johannesburg). The mean values for three replicate analyses are 27.9 ± 5.3 ng Be/g for NIM-D, 138 ± 33 ng Be/g for NIM-P, 419 ± 43 ng Be/g for NIM-N and 2100 ± 360 ng Be/g for NIM-S.

Quasistatic deformation of porous beryllium and aluminum

Loading and unloading of two types of porous beryllium and a porous aluminum under conditions of uniaxial strain, proportional loading, and hydrostatic pressure indicate that yielding is dominated by porosity. Analysis of the data prior to yielding indicates that aspherical pores cause increased compressibility on initial loading. All materials exhibit enhanced compaction when loaded under nonhydrostatic stress conditions. Models which treat the collapse of spherical pores do not agree with the beryllium data, probably because of the influence of aspherical pores and pore-size distribution.