High Helium Content Research Articles

Modeling of Induction Plasma Process for Fullerene Synthesis: Effect of Plasma Gas Composition and Operating Pressure

A mathematical model has been developed on the continuous synthesis of fullerenes by direct evaporation of carbon-containing materials using induction thermal plasma technology. The main purpose of this study is to numerically investigate the effect of plasma gas composition and operating pressure on the fullerene formation. The simulation results confirmed that Ar–He mixture plasma is more efficient than argon plasma in terms of the particle evaporation, generation of fullerene precursors, fullerene growth and their annealing, and that low pressure operation would decrease the overall yield rate of fullerenes by enhancing the radial diffusion of carbon vapors towards the reactor walls. Thus an operating condition of relatively high helium content in the plasma gas and elevated gas pressure seems much more desirable for achieving a high yield rate of fullerenes. This conclusion is in line with the experimental evidences reported previously.

ANALYSIS OF THE NODALISATION INFLUENCE ON SIMULATING ATMOSPHERIC STRATIFICATIONS IN THE EXPERIMENT THAI TH13 WITH THE CONTAINMENT CODE SYSTEM COCOSYS

The activities related to this paper are to investigate the influence of nodalisation on simulating atmospheric stratification in the THAI experiment TH13 (ISP-47) with the German containment code COCOSYS. This article focuses on different nodalisations of the vessel dome, where an atmospheric stratification occurred due to a high helium content. The volume of the dome was divided into several levels that were varied horizontally into different geometries. These geometries differ in the number of zones as well as in the existence of zones that enable the direct rise of an ascending steam plume into the vessel dome. Additionally, the vertical subdivision of the vessel dome was increased to simulate density gradients in a more detailed way. It was pointed out that the proper simulation of atmospheric stratifications and their dissolution depends on both a suitable horizontal as well as vertical nodalisation scheme. Besides, the treatment of fog droplets has an influence if their settlement is not simulated correctly. This report gives an overview of the gained experience and provides nodalisation requirements to simulate atmospheric stratifications and their proper dissolution.

Improvement of luminous efficiency using high helium content in full‐HD plasma‐display panels

Abstract— The influence of the Xe (15%) and He (70%) fractions on the discharge and driving characteristics was compared in 50‐in. full‐HD plasma‐display panels. The same improvement in the luminous efficacy was obtained when increasing either the Xe or He fraction. However, the discharge current with a high He fraction was smaller than that with a high Xe fraction. While the breakdown voltage was hardly influenced by an increase in the He fraction, it was significantly changed when increasing the Xe fraction. The formative and statistical time lags were only slightly changed with a high He fraction, yet significantly increased with a high Xe fraction. In addition, the relatively low luminance and driving‐margin characteristics with a high He fraction were compensated for by controlling the capacitance of the upper dielectric layer.

Improvement of luminous efficiency using high helium content in full‐HD plasma‐display panels

The influence of the Xe (15%) and He (70%) fractions on the discharge and driving characteristics was compared in 50‐in. full‐HD plasma‐display panels. The same improvement in the luminous efficacy was obtained when increasing either the Xe or He fraction. However, the discharge current with a high He fraction was smaller than that with a high Xe fraction. While the breakdown voltage was hardly influenced by an increase in the He fraction, it was significantly changed when increasing the Xe fraction. The formative and statistical time lags were only slightly changed with a high He fraction, yet significantly increased with a high Xe fraction. In addition, the relatively low luminance and driving‐margin characteristics with a high He fraction were compensated for by controlling the capacitance of the upper dielectric layer.

Helium isotope investigation on magnetic reversal boundaries of loess-paleosol sequence at Luochuan, central Chinese Loess Plateau

Extraterrestrial particles have higher 3He/4He ratios than those of terrestrial sediments (> 100 Ra versus < 0.03 Ra, where Ra is the 3He/4He ratio normalized to the atmospheric value of 1.4×10−6). The interplanetary dust particles (IDPs), which are very rich in 3He, continuously bombard the Earth and can accumulate in deposits. IDPs sedimentation rate changes can significantly influence 3He concentration in the Earth surface sediments. Since IDPs are not easy to detect in terrestrial deposits, measuring helium isotopes is a helpful approach to examine changes in IDPs. Helium concentration and helium isotopic composition magnetic substances and the quartz particles were examined for helium concentration and helium isotopic ratio. Results show that the 3He/4He ratio and the 3He concentrations of the magnetic substances are clearly higher than those of the bulk samples and the quartz particles, and, the 3He/4He ratio of the extracted magnetic substances is also higher than that of the average level of the Earth’s crust. The higher helium content in the magnetic fractions can be explained by an influx of IDPs.

Observational Consequences of the Hypothesized Helium‐rich Stellar Population in ω Centauri

In response to the proposed high-helium content stars as an explanation for the double main sequence observed in ω Centauri, we investigated the consequences of such stars elsewhere on the color-magnitude diagram. We concentrated on the horizontal branch, where the effects of high helium are expected to show themselves more clearly. In the process we developed a procedure for comparing the mass loss suffered by differing stellar populations in a physically motivated manner. High-helium stars in the numbers proposed seem absent from the horizontal branch of ω Cen unless their mass-loss history is very different from that of the majority metal-poor stars. It is possible to generate a double main sequence with existing ω Cen stars via accretion of helium-rich pollution consistent with the latest AGB ejecta theoretical yields and such polluted stars are consistent with the observed HB morphology of ω Cen. Polluted models are consistent with observed merging of the main sequences as opposed to our models of helium-rich stars. Using the (B - R)/(B + V + R) statistic, we find that the high-helium bMS stars require an age difference compared to the rMS stars that is too great, whereas the pollution scenario stars have no such conflict for inferred ω Cen mass losses.

Effect of a high helium content on the flow and fracture properties of a 9Cr martensitic steel

An experimental characterization was conducted of helium effects on the mechanical properties of a 9Cr martensitic steel. Six sub-size Charpy samples were implanted in the notch region at 250 °C with 0.25 at.% helium and subsequently tested in 3-point bending at room temperature. Brittle fracture mode (cleavage and intergranular fracture) was systematically observed in the implanted zones of the samples. Finite element calculations of the tests, using as input the tensile properties measured on a helium loaded sample, were performed in order to determine the fracture stress at the onset of brittle crack propagation. Preliminary TEM investigations of the implantation-induced microstructure revealed a high density of small helium bubbles.

Tensile properties of candidate structural materials for high power spallation sources at high helium contents

Low activation 9%Cr martensitic steels EUROFER97, pure tantalum, and low carbon austenitic stainless steel 316L were homogeneously implanted with helium to concentrations up to 5000 appm at temperatures from 70 °C to 400 °C. The specimens were tensile tested at room temperature and at the respective implantation temperatures. In all materials the helium caused an increased in strength and reduction in ductility, with both changes being generally larger at lower implantation and testing temperatures. After implantation some work hardening was retained in 316L and in tantalum, while it almost completely disappeared in EUROFER97. After tensile testing, fracture surfaces were analysed by scanning electron microscopy (SEM). Implantation caused reduction of necking, but up to concentrations of 2500 appm He fracture surface still showed transgranular ductile appearance. Completely brittle intergranular fracture was observed in tantalum at 9000 appm He and is also expected for EUROFER97 at this concentration, according to previous results on similar 9%Cr steels.

東シベリアの石油資源ポテンシャル

A future pipeline project that will transport crude oils from East Siberian fields to Nakhodka, shipping port along the coast of the Japan Sea, is under discussion and gradually revealing its main framework. One of the major concerns is if significant potential of petroleum is expected in the East Siberian region. In this paper, the total of the original oil resources in the region is estimated ranging from 18.9BBO (billion barrel of crude oil) to 67.2BBO.The Siberian platform is consisted of largely uplifted Archean crystalline basement and the overlaid sediments consisted of the Proterozoic and the Lowest Paleozoic formations. Most of the known oil reserves (85%) in the East Siberian region concentrate on the crest of the highest basement uplift on the two arch structures ; Baykit and Nepa-Botuoba. Petroleum source rocks are not concluded yet. Although the Riphean is expected to contain source rocks, it is entirely absent on the most prolific Nepa-Botuoba Arch area. Moreover, most fields have extremely high helium content (ranging 0.2-0.6 percent) with hydrocarbon gases. Based on several unique characteristics of oil and gas fields on the Nepa-Botuoba Arch, the author proposes in this paper that the theory of abiogenic origin can not be ignored ; hydrocarbons associated with helium gases may have migrated upward through the fractures from the depth of the earth.Upon completion of the pipeline linking the supply area (East Siberia) to the market in the Pacific region, oil exploration activities will be accelerated in the East Siberian region. Subsequently, the additional oils derived from the new discoveries in the East Siberian region will fulfill the new pipeline.

Spectroscopic investigations of classical Cepheids and main-sequence stars in galactic open clusters and associations

The small-amplitude Cepheid V1726 Cyg and two members of open cluster Platais 1 (Platais 1 star No. 1 (1921) and Platais 1 star No. 111 (1600)) were investigated, using high-resolution CCD spectra. The following results were obtained: 1) All objects have the same metallicities, close to that of the Sun (for V1726 Cyg weighted average [ Fe/H$]=+0.05$, for Platais 1 star No. 1 (1921) [ Fe/H$]=+0.13$); 2) values of T eff and $\log g$ for the B-stars are in excellent agreement with those determined from $(B-V)$ colour indices using a $(B-V)\sim(T_{\rm eff}$, $\log g$) calibration; 3) the elemental abundances indicate that V1726 Cyg is in the post first dredge-up stage with an age near $1.5 \times 10^{8}$, and is crossing the Cepheid instability strip for the third time. Mean values of $T_{\rm eff}=6100$ K and $\log g=2.35 \pm 0.05$ permit us to refine its colour excess to $E_{B-V}=0\fm 33$, which for a distance of $d = 1568\pm 13$ pc corresponds to $M_{V}=-2\fm 99$. The Cepheid could therefore be pulsating in the fundamental tone, although pulsation in the first overtone is not excluded; 4) Platais 1 star No. 1 (1921) is a slowly rotating HgMn-star with a high helium content, while Platais 1 star No. 111 (1600) is a rapidly rotating main-sequence star with a helium content comparable to that of the Sun; 5) the age of the open cluster is estimated to be about $2.5 \times 10^{8}$ yr.

Geochemical and 3He/4He evidence for mantle and crustal contributions to geothermal fluids in the western Canadian continental margin

Isotopic and geochemical evidence together with helium isotopes are used to identify contributions of deep crustal to upper mantle volatile components in thermal waters at three sites across the western North American plate margin: (1) the low heat-flow forearc of the Cascadia subduction zone; (2) the high heat-flow volcanic arc; and (3) the interior crystalline terrain of the ancestral continental margin.Western continental margin hotsprings issue 50°C, low salinity Na–Cl water and N2 gas with 0.25% CH4. Stable isotopes and 14C indicate local meteoric recharge during the early Holocene. Redox is buffered by sulphate reduction, suggesting that the methane originates from a deeper source. The waters have high helium contents (He/Heair=30) and a 3He-excess (R/Rair=0.27; 3He/3Heair=8), representing a mixture of radiogenic 4He production in crystalline rock with >10% He from subducted oceanic crust. Geophysical data indicate fluid-filled discontinuities in the subduction zone that may provide a pathway for He, and possibly for CH4 and a saline fluid component from depth.In the Garibaldi belt of Quaternary arc-volcanism, 60°C Na–Cl hotsprings and 200°C geothermal well waters discharge from fractures in the basement rocks. δ18O and δ2H show the thermal waters to be a mixture of local recharge with up to 8% “andesitic” water from the upper mantle. He isotopes indicate a mantle origin (R/Rair=6.0), with a minor crustal signature, consistent with observations in the Cascadia range to the south and at other circum-Pacific volcanic arc settings. High PCO2, an enriched δ13CDIC, elevated 3He/CO2 ratios and elevated Cl− are likely to be derived from subducted Juan de Fuca plate sediments and pore waters.Thermal Na–SO4 waters (up to 58°C) from the Omineca Crystalline Belt are locally recharged and have an unusually rapid circulation time of less than 40years. This contrasts with their high radiogenic He content (176×10−7cc/g) with minimal mantle input (R/Rair=0.06). The underlying Columbia River Fault Zone is the likely pathway for helium migration from depth.

Wide‐Field CCD Photometry of the Globular Cluster M30

We present new VI photometry for the halo globular cluster M30 (NGC 7099=C2137-174) and compute luminosity functions (LFs) in both bands for samples of about 15,000 hydrogen-burning stars from near the tip of the red giant branch (RGB) to over 4 mag below the main-sequence (MS) turnoff (TO). We confirm previously observed features of the LF that are at odds with canonical theoretical predictions: an excess of stars on subgiant branch (SGB) approximately 0.4 mag above the turnoff and an excess number of RGB stars relative to MS stars. Based on subdwarfs with Hipparcos-measured parallaxes, we compute apparent distance moduli of (m-M)V=14.87 ± 0.12 and 14.65 ± 0.12 for reddenings of E(V-I)=0.06 and 0.02, respectively. The implied luminosity for the horizontal branch (HB) at these distances is MHBV=0.11 and 0.37 mag. The two helium indicators we have been able to measure (R and Δ) both indicate that M30's helium content is high relative to those in other clusters of similar metallicity. M30 has a larger value for the parameter ΔVHBTO than any of the other similarly metal-poor clusters for which this quantity can be reliably measured. This suggests that M30 has either a larger age or higher helium content than all of the other metal-poor clusters examined. The color-difference method for measuring relative ages indicates that M30 is coeval with the metal-poor clusters M68 and M92.

Radon in various environmental samples in the Herculane Spa, Cerna Valley, Romania

Early measurements in the Herculane Spa region showed high helium content (6 mL/L) and high radon concentrations (up to 7.4 MBq m −3) for the emanated gases which accompany geothermal waters originating in the hydrogeothermal deposit existing in this area. This paper presents new data on the radon exhalation rate from soil, and indoor radon in some buildings in this resort. The greater values obtained in two places for radon flux are probably caused by transversal faults in this area. In the winter, the indoor radon mean value is two times greater than the summer value. The Ra, U, Th, and K content for six soils sampled in the vicinity of the site of radon flux measurement were also determined. The values obtained are somewhat higher than the values expected as a consequence of surface granitic rocks in this region. Large 137Cs deposits were found (up to 950 Bq kg −1).

Studies on the occurrence of radon in selected sites of Romania

Experimental data presented in this paper have their origin in the first Romanian investigations in connection with the helium content in mineral and geothermal water sources. The high radon presence in the emanated gases from the water sources is a reliable indication of high helium content. The work also presents measurements in connection with the indoor radon content and the radon exhalation from soil in some regions from Transylvania. An attempt has been made to correlate the radon flux data with the indoor radon concentrations.

Technology of the recovery of helium from Bratsk condensed gas deposit

The close location of gas consumers to Bratsk condensed gas deposit and its high helium content have made it possible to organize the economical processing of gas and with small volumes of output (of the order of 440 million m{sup 3}/yr) to obtain each year more than 1 million m{sup 3} of helium, 421 million m{sup 3} of commercial gas, up to 3 thousand tons of liquefied gases, 16.4 thousand tons of gasoline fraction, 35 tons thousand of diesel fuel, and 2.5 thousand tons of boiler fuel. The formation gas contains (in vol. %): helium (0.27), hydrogen (0.12), carbon dioxide (0.24), methane (over 86), propane and butane (1.7), condensate (2.4), and also ethane and nitrogen. The materials from the industrial treatment of gas and condensate and their processing stages are combined in a single complex. The processing of gas and condensate extracted at the industrial separation plant is discussed. In the technology developed for the separation of helium, the energy of the gas itself is principally used, and preliminary absorption (or adsorption) purification of the gas to remove traces of carbon dioxide, a propane cooling unit, or additional compressors for transporting gas to the consumer are not required. Only inmore » the latter stages of helium concentration and its purification is a circulatory compressor used to obtain liquid nitrogen.« less

Oscillations of solar models with internal element diffusion

view Abstract Citations (176) References (94) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Oscillations of Solar Models with Internal Element Diffusion Cox, Arthur N. ; Guzik, Joyce A. ; Kidman, Russell B. Abstract Data on the evolution of a solar model are presented which include the effects of diffusive processes that lead to a partial sorting of the elements with depth. The two models are with and without the effects of diffusion. The diffusion process of gravitational settling, composition gradient diffusion, and thermal diffusion are based on the method of Iben and MacDonald (1985). It is found that a high original helium content is required to match the observed global oscillation data, and that the total neutrino flux detectable by the chlorine detector accordingly is increased to over 10 SNU. Publication: The Astrophysical Journal Pub Date: July 1989 DOI: 10.1086/167675 Bibcode: 1989ApJ...342.1187C Keywords: Particle Diffusion; Solar Interior; Solar Oscillations; Stellar Models; Opacity; Solar Diameter; Solar Radiation; Stellar Evolution; Stellar Mass; Thermal Diffusion; Solar Physics; DIFFUSION; SUN: INTERIOR; SUN: OSCILLATIONS full text sources ADS |

The age and helium content of the eclipsing binary AI Phoenicis

view Abstract Citations (22) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The age and helium content of the eclipsing binary AI Phoenicis. Vandenberg, D. A. ; Hrivnak, B. J. Abstract Comparisons of new theoretical isochrones for heavy-element abundances Z = 0.0169 (solar) and Z = 0.04 with recently published parameters of AI Phoenicis suggest that this system has an age of approximately (3.6 + or - 0.7) x 10 to the 9th yr and a helium content of Y = 0.38 + or - 0.05. The indicated uncertainty is largely due to the lack of precise knowledge about the metallicity of the binary, since the fits to the data by both sets of isochrones are exceedingly good. The high helium content, which is required in order to reproduce the observed mass-luminosity relation, is suggested to be comparable with the values generally derived for binaries if the latter are adjusted to take into account the effects of the new Los Alamos opacities. Publication: The Astrophysical Journal Pub Date: April 1985 DOI: 10.1086/163065 Bibcode: 1985ApJ...291..270V Keywords: Abundance; Chronology; Eclipsing Binary Stars; Metallicity; Stellar Evolution; Helium; Astrophysics full text sources ADS | data products SIMBAD (1)

Isotopic and chemical composition of parbati valley geothermal discharges, North-West Himalaya, India

The isotopic compositions of the waters discharged from Parbati Valley geothermal areas indicate a higher altitude meteoric origin, with discharge temperatures reflecting variations in the depth of penetration of the waters to levels heated by the existence of a ‘normal’ geothermal gradient. On the basis of mixing models involving silica, tritium, discharge temperatures and chloride contents, deep equilibration temperatures of 120–140°C were obtained for Manikaran, possibly reaching 160°C at even greater depth. Geothermometers based on sulfate-water 18O exchange and gas reactions point to similar temperatures. Exceptionally high helium contents of the discharges correspond to apparent crustal residence times of the waters in the order of 10–100 Ma; relative nitrogen-argon contents support a largely meteoric origin of the waters with a possible fossil brine, but no detectable magmatic component.

Nucleosynthesis in bouncing cosmologies

It is shown that certain anomalies connected with the primordial abundances of light nuclei may be resolved if it is assumed that the Universe oscillates between phases of finite densities. Since general relativity does not produce bouncing models of the Universe, such models are obtained through the introduction of a negative energy scalar field of zero rest mass. It is shown that all the relevant parameters of the dynamics of the model and the nucleosynthesis in it are determined by observations and that a self-consistent picture emerges. The model is capable of admitting more than three neutrino flavours without an embarrassingly high primordial helium content. It is also shown that the calculations could be adapted to described production of light nuclei in compact massive bouncing objects.

Simulation of Fusion First-Wall Environment in a Fission Reactor

A novel concept to produce a realistic simulation of a fusion first-wall test environment has been proposed recently. This concept takes advantage of the (n, α) reaction in 59Ni to produce a high internal helium content in the metal while using the 3He (n, ρ)T reaction in the gas surrounding the specimen to produce an external heat and particle flux. Models to calculate heat flux, erosion rate, implantation, and damage rate to the walls of the test module are presented. Preliminary results show that a number of important fusion technology issues could be tested experimentally in a fission reactor such as the Engineering Test Reactor.