Helium Component Research Articles

LOCAL INTERSTELLAR NEUTRAL HYDROGEN SAMPLED IN SITU BY IBEX

Hydrogen gas is the dominant component of the local interstellar medium. However, due to ionization and interaction with the heliosphere, direct sampling of neutral hydrogen in the inner heliosphere is more difficult than sampling the local interstellar neutral helium, which penetrates deep into the heliosphere. In this paper we report on the first detailed analysis of the direct sampling of neutral hydrogen from the local interstellar medium. We confirm that the arrival direction of hydrogen is offset from that of the local Helium component. We further report the discovery of a variation of the penetrating Hydrogen over the first two years of IBEX observations. Observations are consistent with hydrogen experiencing an effective ratio of outward solar radiation pressure to inward gravitational force greater than unity ({\mu}>1); the temporal change observed in the local interstellar hydrogen flux can be explained with solar variability.

Spatial variations in gas and stable isotope compositions of thermal fluids around Lake Van: Implications for crust–mantle dynamics in eastern Turkey

We investigate the helium (3He/4He) and carbon (δ13C) isotope compositions and relative abundance ratios (CO2/3He) of gas samples together with the stable isotope compositions of dissolved carbon and sulfur and the oxygen and hydrogen isotopic compositions of the associated water phase from a number of geothermal fields located around Lake Van in eastern Anatolia, Turkey. The mantle-derived helium component, which is likely transferred to the crust beneath eastern Turkey by recent magmatism, is found to constitute up to 96% (e.g. Nemrut Caldera) of the total He content in fluids. As regards the spatial distribution of He, samples collected from areas of Pliocene–Quaternary volcanics are characterized by a wide and generally higher range of R/RA ratios (0.93 to 7.76 RA) compared to those of non-volcanic regions (0.85 to 1.0 RA). CO2/3He ratios vary over a wide range (2.4×105–3.8×1013) but are mostly higher than that of the nominal upper mantle (~2×109). Oxygen–hydrogen isotope values of the waters are conformable with the Global Meteoric Water Line and indicate a local meteoric origin. Sulfate in waters is most probably derived from dissolution of marine carbonates and terrestrial evaporite units. Temperatures calculated by SO4–H2O isotope geothermometry lie between 40 and 199°C, and are in poor agreement with reservoir temperatures estimated from silica geothermometers. Discordant temperatures may be due to either the relatively slow rate of isotopic equilibrium between water and sulfate or mixing of geothermal water with sulfate-bearing shallow waters which may modify the δ18O value. The δ13C (CO2) values of gas samples are consistently lower than those of their water counterparts, consistent with loss of CO2 from waters by degassing. Mixing between mantle and various crustal C-sources appears to be the main control on the C-isotope composition. The principal origin of CO2 in all samples is crustal lithologies, mainly limestone (~85 to 98% of the total carbon inventory): thus, the crustal carbon flux is at least 10 times that from the mantle. There is a broad correlation between high 3He/4He values and thinner crust in the western part of the Lake Van region, where several historically-active volcanoes are located. This observation indicates that localized volcanic and magmatic activity exerts the primary control on the balance between mantle and crustally-derived volatiles in the region.

Stark broadening parameters calculation of the allowed 4471 Å line and forbidden 4470 Å component of neutral helium with different electric microfield distribution functions

The influence of an electric microfield distribution function (EMDF) on line shapes and on Stark broadening parameters is studied. For this purpose, we use different EMDFs obtained by theoretical calculations and computer simulation methods to calculate the allowed 4471 Å neutral helium line and its forbidden 4470 Å component. Correlation effects are shown by considering different categories of plasmas, weakly coupled plasmas and strongly coupled plasmas, with large gaps of temperature and density.

RAPHAEL: Developing major V/HTR technology

The FP6 RAPHAEL Integrated Project on V/HTR technology concluded in April 2010 after 5 years of successful performance. 35 partners from 10 Member States, an overall budget above 18 MEUR and about 170 key deliverables are some important figures of the project.RAPHAEL provides results in seven V/HTR technology areas: core physics, fuel, fuel cycle back end, materials, components, safety and system integration covering the major systems and components of a V/HTR. Major highlights include design, fabrication and testing of innovative helium components, improved fuel fabrication and fuel and materials irradiation, and safety testing and PIE of irradiated fuel. In the area of coupled reactor physics and core thermo fluid dynamics, benchmarks have been performed on core safety experiments on the AVR and HTR10 high temperature test reactors, and on the HFR EU1bis fuel burn-up experiment. The fuel cycle back-end activities cover characterisation of V/HTR-specific waste, disposal behaviour and conditioning and spent fuel performance modelling. The materials activities comprise vessel and high-temperature materials, the latter work in collaboration with EXTREMAT, and graphite irradiation and characterisation. Safety and licensing assessments of a V/HTR, and the system integration aspects with respect to plant reference data and R&D results complete the comprehensive scope of RAPHAEL.Selected results will be made available as Euratom input for exchange within the GIF VHTR projects in negotiated procedures.Two advisory groups (safety-SAG and industrial users-IUAG) accompanied the project and provided valuable input regarding adjustment of concept specifications. The recommendations of the Industrial Users Advisory Group, including major end-users, are used as input to EUROPAIRS, an FP7 support action aiming at integrating end-users into the R&D process towards a demonstrator for cogeneration.To address the key issue of knowledge transfer, RAPHAEL conducted three Eurocourses, with support of the IAEA, to transmit V/HTR physics and technology to young engineers and students. Furthermore, RAPHAEL was regularly present in conferences and has issued numerous technical publications.RAPHAEL executed intensive international collaboration mainly in the areas of materials and fuel, in particular with Korea, and in safety. In addition, its representation and contribution was often requested in collaboration initiatives of Euratom with Russia and China, and in workshops organised by IAEA.

The Cosmic Ray Primary Spectrum in the Transition Region between Direct and Indirect Measurements (10 TeV–10 PeV)

The cosmic ray primary spectrum between 10 TeV and 10 PeV is a key region to understand the origin and the acceleration processes of the galactic radiation. Around 100 TeV measurements performed by balloons and air shower arrays partially overlap. The experimental results recently obtained by both techniques are summarized. The picture that comes out from a common interpretation of the data is a steeper proton spectrum compared to the helium, CNO, and iron groups with a dominance of the helium component in the knee region. The agreement on the proton spectrum by balloons and air shower arrays is remarkable. The all particle spectrum obtained from the fit of the single mass groups reproduces fairly well the world average experimental all particle spectrum in the 10 TeV–10 PeV region.

The cosmic ray primary spectrum in the transition region between direct and indirect measurements (10 TeV - 10 PeV)

The cosmic ray spectrum between 10 TeV and 10 PeV is a key region to understand the origin and the acceleration processes of the galactic radiation. Around 100 TeV measurements performed by balloons and air shower arrays partially overlap. The experimental results recently obtained by both techniques are summarized. The picture that comes out from a common interpretation of the data is a steeper proton spectrum compared to the helium and CNO groups with a dominance of the helium component in the knee region. The agreeement on the proton spectrum by balloons and air shower arrays is remarkable.

Constraints on the loss of matrix-sited helium during vacuum crushing of mafic phenocrysts

Vacuum crushing is an efficient technique to selectively release the mantle-derived helium component trapped within olivine and pyroxene phenocrysts. However, contrary to previous assumptions, recent studies have shown that this method may liberate significant matrix-sited cosmogenic 3He ( 3He c) or radiogenic 4He ( 4He ∗). Because this loss may bias both the determination of magmatic 3He/ 4He ratios and the accuracy of 3He c measurements, it is essential to understand what mechanism is responsible and under what conditions matrix helium loss is manifest. To address this question, olivines and pyroxenes with various amounts of matrix-sited 3He (from 10 7 to 10 11 at. g −1) were crushed in air or in vacuum using several crushing devices. Sample temperature was controlled during each crushing experiment, and ranged from 25 to 325 °C. The resulting powders were then sieved to obtain several homogeneous grain fractions ranging between <10 and >300 μm. The 3He c concentrations measured in each fraction clearly show that significant 3He c loss (>20%) affects only the finest fraction (<10 μm) and, importantly, only under hot conditions (here T ⩾300 °C). Even the smallest fractions (<10 μm) quantitatively retain matrix-sited 3He c when crushed under cold conditions ( T ⩽25 °C), regardless of the duration and energy of crushing. These results invalidate the model previously proposed by (Yokochi R., Marty B., Pik R. and Burnard P. (2005) High 3He/ 4He ratios in peridotite xenoliths from SW Japan revisited: evidence for cosmogenic 3He released by vacuum crushing. Geochem. Geophys. Geosyst. 6, doi:10.1029/2004GC000836) that involved spallation tracks and implied that the magnitude of loss was mainly controlled by the grain size. Moreover, new diffusion experiments were carried out to constrain the diffusivity of matrix-sited helium in crushed olivines. When used to model diffusive 3He c loss as a function of grain size during crushing, these new data predict the observed release fairly well. Therefore, we conclude that temperature-enhanced volume diffusion is one of the main mechanisms controlling the release of 3He c during crushing. For future applications, special attention should thus be paid to control the grain size, the crushing duration, and the temperature of the sample.

He–Ar and Nd–Sr isotopic compositions of late Pleistocene felsic plutonic back arc basin rocks from Ulleungdo volcanic island, South Korea: Implications for the genesis of young plutonic rocks in a back arc basin

We report analyses of noble gases and Nd–Sr isotopes in mineral separates and whole rocks of late Pleistocene (< 0.2 Ma) monzonites from Ulleungdo, South Korea, a volcanic island within the back arc basin of the Japan island arc. A Rb–Sr mineral isochron age for the monzonites is 0.12 ± 0.01 Ma. K–Ar biotite ages from the same samples gave relatively concordant ages of 0.19 ± 0.01and 0.22 ± 0.01 Ma. 40Ar/ 39Ar yields a similar age of 0.29 ± 0.09 Ma. Geochemical characteristics of the felsic plutonic rocks, which are silica oversaturated alkali felsic rocks (av., 12.5 wt% in K 2O + Na 2O), are similar to those of 30 alkali volcanics from Ulleungdo in terms of concentrations of major, trace and REE elements. The initial Nd–Sr isotopic ratios of the monzonites ( 87Sr/ 86Sr = 0.70454–0.71264, 143Nd/ 144Nd = 0.512528–0.512577) are comparable with those of the alkali volcanics ( 87Sr/ 86Sr = 0.70466–0.70892, 143Nd/ 144Nd = 0.512521–0.512615) erupted in Stage 3 of Ulleungdo volcanism (0.24–0.47 Ma). The high initial 87Sr/ 86Sr values of the monzonites imply that seawater and crustally contaminated pre-existing trachytes may have been melted or assimilated during differentiation of the alkali basaltic magma. A mantle helium component ( 3He/ 4He ratio of up to 6.5 RA) associated with excess argon was found in the monzonites. Feldspar and biotite have preferentially lost helium during slow cooling at depth and/or during their transportation to the surface in a hot host magma. The source magma noble gas isotopic features are well preserved in fluid inclusions in hornblende, and indicate that the magma may be directly derived from subcontinental lithospheric mantle metasomatized by an ancient subduction process, or may have formed as a mixture of MORB-like mantle and crustal components. The radiometric ages, geochemical and Nd–Sr isotopic signatures of the Ulleungdo monzonites as well as the presence of mantle-derived helium and argon, suggests that these felsic plutonic rocks evolved from alkali basaltic magma that formed by partial melting of subcontinental lithospheric mantle beneath the back arc basin located along the active continental margin of the southeastern part of the Eurasian plate.

Cosmic ray data and their interpretation: about the Tibet Shower Array: Chemical Composition of Cosmic Rays at the Knee Viewed from the Tibet Air Shower Experiment

A brief summary is given about present status of composition measurement of cosmic rays by direct observations and indirect ones which provides key information on the origin of the cosmic rays. The result of Tibet hybrid experiment measuring proton and helium spectra at the knee is presented, in which the decreasing fractions of both of the proton and helium component to the all particle spectrum with increasing energy are observed suggesting that the knee is dominated by heavy nuclei. It is planed to explicitly measure the iron spectrum at the knee by detecting the core structure of the air showers in the next phase of Tibet experiment ‘YAC’ ( Y angbajing A ir shower C ore array).

Dynamics of superfluid 4He: Two-scale approach

The paper explores the two scale approach to the incompressible dynamics of superfluid 4He. The fluid is described by a system of equations: Navier–Stokes and Euler equations for the macroscopic normal and superfluid velocity fields respectively. The two equations couple via a mutual friction force exerted on superfluid (quantum) vortices by the normal component. The magnitude of this force, calculated via the analysis of dynamics of quantum vortices in the microscopic scale, is proportional to the value of the counterflow (relative velocity of two helium components) and to the density of quantum vortices. The latter is determined by the generalized Vinen equation, adequate for flows having a net macroscopic vorticity. The generalized equation includes the drift of the anisotropic vortex tangle caused by Magnus force. The derived system of equations is applied first to the analysis of steady state solution of rotating turbulence, and then to the numerical analysis of formation of plane Couette flow between two infinite parallel material surfaces z = 0 and z = D . For t < 0 both surfaces and the fluid are at rest, then at t = 0 one material surface starts moving along the x axis with velocity V 0 . The viscosity forces cause the motion of normal component and the counterflow which make the line-length density grow, and the two components become coupled by the mutual friction. The fact that superfluid velocity tends to match with the normal velocity makes that ω s ≠ 0 , which implies polarization and drift of the tangle. At a given temperature the dynamics depends solely on D V 0 .

Mean kinetic energy of helium atoms in fluid3He and 3He–4He mixtures

Momentum distributions and mean kinetic energies of helium atoms, in pure fluid3He and3He–4He mixtures,at T = 2 K and3He concentrationsof x = 0.20 and x = 1.00, are presented. The experimental technique employed is deep inelastic neutronscattering measurements in the eV energy range, with wavevector transfer of typically100 Å−1<q<250 Å−1. Single-particledynamical properties of 3He–4He mixtures are discussed in the context of previous results on mixtures at different concentrations and pure3He and4He. In the pure fluids,the kinetic energy of 3He and 4He are remarkably similar for molar volumes above25 cm3 mol−1, whilefor smaller molar volumes, upon approaching the liquid–solid transition, the kinetic energy is largerin 3He than 4He. On the other hand, the short-time dynamics of the heliummixture reveal quite a different picture with respect to the pure3He and 4He: the momentum distribution and mean kinetic energy of the light helium component areindependent of the molar volume and concentration.

Release of mantle helium from forearc region of the Southwest Japan arc

Shikoku, Japan, is an island located on the forearc region of the western sector of the Southwest (SW) Japan arc that was formed by subduction of the Philippine Sea plate beneath the Eurasian plate. Noble gas isotope analyses were carried out for 30 bubbling gas samples and spring water samples collected in Shikoku. In addition, chemical and carbon isotope analyses were conducted for six gas samples. Observed 3He/ 4He ratios were 0.17 R/R A to 3.56 R/R A, showing that several samples contain mantle helium components, although some samples contain helium of crustal origin. Geographical distributions of 3He/ 4He ratios show that high 3He/ 4He ratios originate mainly from two areas: one along the Median Tectonic Line (MTL), a major active fault in Japan; the other coinciding with a region in which non-volcanic long-period tremors occur, about 30 km deep [Obara, K., 2002. Nonvolcanic deep tremor associated with subduction in southwest Japan. Science 296, 1679-1681]. This fact indicates that fluids liberated from the slab in the forearc region cause deep tremors and fracturing within the crust, thereby easing the transfer of fluids to the surface that are mixed with mantle helium to the surface. An active fault system can also provide an efficient path for mantle helium transfer.

Energy Spectra of Prompt Gamma Rays from Al and Fe Thick Targets Irradiated by Helium and Proton Beams: Concerning Planetary Gamma-Ray Spectroscopy

Bombardment experiments with thick targets made of each of Al and Fe were performed using 230 MeV/nucleon helium and 210 MeV proton beams. The energies and intensities of prompt gamma rays emitted by inelastic nuclear scattering of energetic neutrons were measured by a high-purity Ge detector. This work presents the first experimental results concerning the emission of prompt gamma rays from thick targets anticipated by helium component in galactic cosmic rays, since no foregoing work related to this one has been done. It is concluded that helium has the capability of prompt gamma ray line emission through the inelastic nuclear reaction of neutrons with target material by a factor of 3.5 on average in comparison with proton. As regards the lunar and planetary nuclear spectroscopy, a consideration is given on the role of helium particles to the total production of gamma rays emitted from a planetary surface.

High Energy Galactic Cosmic Rays Observed by RUNJOB Experiment

Galactic cosmic rays (GCRs) from proton to iron with the energy of 1013 - 1015 eV were observed by RUssia-Nippon JOint Balloon (RUNJOB) experiments. Each energy spectrum of the primary nuclear components except for helium is in agreement with the results obtained by other observations in the same energy region as the RUNJOB observation within statistical errors, while the intensity of the helium component is nearly half that obtained by the JACEE and the SOKOL observations. The spectrum slopes seem to be almost parallel or become gradually harder as mass becomes heavier. The power indices of the spectra are nearly −2.75 in the energy range of 20 - 500 TeV/nucleous. These our results support the acceleration mechanism and the propagation process in Galaxy of GCRs depend on its rigidity.

Measurements and analysis of collisional line-mixing within nuclear hyperfine components of helium broadened HI lines

The absorption by the R (0) and R (1) lines of the fundamental band of HI broadened by He have been measured in the 0–500 mbar pressure range using a tunable difference frequency generation laser spectrometer. The observed transmissions have been fitted and analyzed with a line-coupling model based on the infinite order sudden approximation. It is demonstrated that the three hyperfine components of the R (0) manifold have identical widths and are not coupled by collisions. On the contrary, the profile of the R (1) manifold cannot be modeled without accounting for both line-mixing and for the fact that the nine hyperfine components have different broadening parameters. This is, to our knowledge, the first demonstration of line coupling within hyperfine components.

A model for the population of helium stars in the Galaxy: Low-mass stars

We model the Galactic ensemble of helium stars using population synthesis techniques, assuming that all helium stars are formed in binaries. In this picture, single helium stars are produced by mergers of helium remnants of the components of close binaries (mainly, the merging of helium white dwarfs) or in the disruption of binaries with helium components during supernova explosions. The estimated total birthrate of helium stars in the Galaxy is 0.043 yr−1; the total number is 4 × 106; and the binarity rate is 76%. We construct a subsample of low-mass (M He ≲ 2M ⊙) helium stars defined by observational selection effects: the limiting magnitude (V He ≤ 16), ratio of the magnitudes of the components in binaries (V He ≤ V comp), and lower limit for the semiamplitude of the radial velocity required for detecting binarity (K min = 30 km s−1). The parameters of this subsample are in satisfactory agreement with observations of helium subdwarfs. In particular, the binarity rate in the selection-limited sample is 58%. We analyze the relations between the orbital periods and masses of helium subdwarfs and their companions in systems with various combinations of components. We predict that the overwhelming majority (∼97%) of unobserved companions to helium stars will be white dwarfs, predominantly, carbon-oxygen white dwarfs.

Cosmic-Ray Spectra and Composition in the Energy Range of 10-1000 TeV per Particle Obtained by the RUNJOB Experiment

This is a full report on the cosmic-ray spectra and composition obtained by the emulsion chambers on board 10 long-duration balloons, launched from Kamchatka between 1995 and 1999. The total exposure of these campaigns amounts to 575 m2 hr, with an average flight altitude of ~32 km. We present final results on the energy spectra of two light elements, protons and helium nuclei, and on those of three heavy-element groups, CNO, NeMgSi, and Fe, covering the very high energy region of 10-1000 TeV particle-1. We additionally present the secondary/primary ratio, the all-particle spectrum, and the average mass of the primary cosmic rays. We find that our proton spectrum is in good agreement with other results, but the intensity of the helium component is nearly half that obtained by JACEE and SOKOL. The slopes of the spectra of these two elements obtained from RUNJOB data are almost parallel, with values of 2.7-2.8 in the energy range of 10-500 TeV nucleon-1. RUNJOB heavy-component spectra are in agreement with the extrapolation from those at lower energies obtained by CRN (Chicago group), monotonically decreasing with energy. We have also observed secondary components, such as the LiBeB group and the sub-Fe group, and present the secondary/primary ratio in the TeV nucleon-1 region. We determine the all-particle spectrum and the average mass of the primary cosmic rays in the energy region of 20-1000 TeV particle-1. The intensity of the RUNJOB all-particle spectrum is 40%-50% less than those obtained by JACEE and SOKOL, and the RUNJOB average mass remains almost constant up to ~1 PeV.

Kerr Effect in Liquid Helium at Temperatures Below the Superfluid Transition

The electro-optical Kerr effect induced by a slowly varying electric field in liquid helium at temperatures below the lambda point is investigated. The Kerr constant of liquid helium is measured to be (1.43+/-0.02(stat)+/-0.04(sys)) x 10(-20) (cm/V)(2) at T=1.5 K. Within experimental uncertainty, the Kerr constant is independent of temperature in the range T=1.5 K to 2.17 K, which implies that the Kerr constant of the superfluid component of liquid helium is the same as that of normal liquid helium. Pair and higher correlations of He atoms in the liquid phase account for about 23% of the measured Kerr constant. Liquid nitrogen was used to test the experimental setup; the result for the liquid nitrogen Kerr constant is (4.38+/-0.15) x 10(-18) (cm/V)(2). Kerr effect can be used as a noncontact technique for measuring the magnitude and mapping out the distribution of electric fields inside these cryogenic insulants.

Turbulent dissipation near absolute zero

The superfluid component of liquid helium has exactly zero viscosity and its rotational motion is constrained by quantum mechanics to very thin vortex filaments of the same circulation. When liquid helium is made turbulent the vortex filaments form a disordered tangle. This article critically reviews recent experiments and calculations to explain the surprising observation that near absolute zero, in the absence of viscous effects, turbulent kinetic energy decays, and to highlight similarities and differences between superfluid turbulence and ordinary classical turbulence.

Anomalous helium ions as the source of energetic helium atoms in the outer heliosphere

The helium component of the anomalous cosmic rays (ACR) is a potential source of neutral energetic helium due to charge-exchange of the He + ions with the hydrogen or helium atoms from the background. The most effective source of the energetic helium atoms should correspond to the relatively low-energy (up to 100 keV/n) ions present in the regions near and beyond the solar wind termination shock. The energetic neutral atoms (ENA) of ACR origin are therefore generated in the distant heliosphere and can provide a means of remote observation of this region. We present the results of numerical calculations of the anomalous helium spectrum and spatial density in a model heliosphere and of the corresponding energetic helium flux. The results are compared with the data obtained by SOHO. We point out that the helium data, covering different region of energy-per-nucleon values, are an important supplement to the hydrogen SOHO data and can be used to test the hypotheses about the origin of the signal.