Hydrogen Helium Research Articles

Fully Quantum Cross Second Virial Coefficients for the Three-Dimensional He–H $$_{2}$$ 2 Pair

A recent high-accuracy three-dimensional potential is used to compute the cross second virial coefficient $$B_{12}(T)$$ between helium and molecular hydrogen. These calculations fully account for both quantum effects (with the path-integral Monte Carlo method) and the flexibility of the hydrogen molecule. The effect of flexibility is relatively small (only slightly larger than the expanded uncertainty of our results), but the full quantum mechanical approach is essential to obtain correct results at cryogenic temperatures. Values are calculated from 8 K to 2000 K; the uncertainty of the potential is propagated into uncertainties of $$B_{12}$$ . Similar calculations are performed for He with the isotopologues D $$_{2}$$ , T $$_{2}$$ , HD, HT, and DT. Comparison is made with the experimental data for the He/H $$_{2}$$ binary, and with the limited data available for He/D $$_{2}$$ and He/HD. The calculated $$B_{12}(T)$$ ’s are generally consistent with the experimental results, but have lower uncertainties.

The centimeter-wavelength opacity of ammonia under deep jovian conditions

Extensive measurements of the centimeter-wavelength opacity of ammonia have been conducted under simulated deep jovian conditions using an ultra-high-pressure measurement system built at Georgia Tech. Over 1000 measurements of the opacity of ammonia have been conducted in the 5–20cm wavelength range under simulated jovian conditions (pressures ranging from 0.05 to 99bars, temperatures from 330 to 500K) in a hydrogen–helium atmosphere. These and previous measurements conducted by Hanley et al. (Hanley et al. [2009]. Icarus, 202, 316–355) and Devaraj et al. (Devaraj et al. [2011]. Icarus, 212, 224–235) have been used to empirically derive a consistent ammonia opacity model for the 2mm–20cm wavelength range under the pressure and temperature conditions characteristic of the middle and deep jovian atmosphere. This model can be used reliably in the millimeter-wavelength range up to 3bars of pressure and temperatures up to 300K and in the centimeter-wavelength range up to 100bars of pressure and temperatures up to 500K. In addition, over 800 measurements of the 5–20cm wavelength opacity of ammonia pressure-broadened by water vapor, hydrogen and helium have been conducted under simulated deep jovian conditions for the first time to study the influence of water vapor on the ammonia absorption spectrum. Based on these measurements, a new model has been developed. These laboratory data and the model show that water vapor has a measurable effect on the opacity of ammonia under jovian conditions. The laboratory study and the models will help to improve our understanding of centimeter-wavelength absorption by ammonia in the jovian planets in general, and specifically, will improve retrievals of ammonia and water vapor from the Juno microwave radiometer (MWR) at Jupiter.

Effect of the displacement damage from argon ion irradiation on the synergistic effect of helium–hydrogen in tungsten

The effect of argon ion pre-irradiation on helium and hydrogen ion irradiation was investigated in tungsten. At the same time, comparative experiments were carried out on the irradiation of helium and hydrogen ions in tungsten. Without the argon ion irradiation, the energy of 35keV hydrogen ions mainly accelerated the coalescence of defects created by the 60keV helium ions, the irradiation damage degree increased with hydrogen ion fluence increasing. With the argon ion irradiation, lots of voids were created by argon ion irradiation, which increased the helium and hydrogen retention and the synergistic effect of helium–hydrogen in tungsten. In the same hydrogen fluence, the surface damage degree with argon ion pre-irradiation was higher than that without argon ion pre-irradiation.

A First Simulation Study of Hydrogen Isotope Accumulation and Diffusion in Tungsten First Wall of HiPER Inertial Fusion Facility

The study of the retention and desorption of hydrogen isotopes and helium atoms in first-wall materials is key for the design of future fusion reactors, not only for the effect of the materials on the degradation of the wall properties but also for the implications in tritium management strategies.A diffusion model of the implanted H, D, T, and He species in a 1-mm-thick first wall of tungsten for the two initial phases of the proposed European laser fusion project HiPER (namely, phases 4a and 4b) has been implemented using the tritium migration analysis program TMAP7. The effects of the abrupt temperature increases, working temperatures, and the operational pulsing modes on the diffusion are studied. Although a detailed treatment of the different trapping mechanisms has been omitted, meaningful quantitative results on the accumulation, desorption, and time intervals to reach a stationary state are presented and discussed.

Limiting explosible concentration of hydrogen–oxygen–helium mixtures related to the practical operational case

This paper presents data on the limiting (minimum) concentrations of hydrogen in oxygen, in the presence of added helium, at elevated temperature and pressure related to the practical operational case. A 5 L explosion vessel, an ignition sub-system and a transient pressure measurement sub-system were used. Through a series of experiments carried out using this system, the limiting concentrations of hydrogen in oxygen and helium at different initial pressures and temperatures for the practical operational case were studied, and the influence of ignition energy and initial temperature on the limiting concentration of hydrogen in oxygen and helium was analyzed and discussed. The variation of ignition energy within the studied range is found to have a significant effect on the limiting concentration of hydrogen in oxygen and helium at lower initial temperature. However, when the ignition energy is higher than 32 mJ, the limiting hydrogen concentration remains almost changeless as the initial temperature increases from 21 °C to 90 °C. The limiting explosible concentration of hydrogen–oxygen–helium mixture decreases as the ignition energy increases when the initial temperature is lower. When the initial temperature is higher, the ignition energy has little effect on the limiting hydrogen concentration of hydrogen–oxygen–helium mixtures. When the initial temperature reaches 90 °C, the limiting hydrogen concentration remains almost changeless with an increase in ignition energy. The limiting explosible concentration of hydrogen in the mixtures, at the initial temperature of 21 °C and the ignition energy of 0.5 mJ, is 8.5% and that of oxygen is 11.25%.

AMR (Active Magnetic Regenerative) refrigeration for low temperature

This paper reviews AMR (Active Magnetic Regenerative) refrigeration technology for low temperature applications that is a novel cooling method to expand the temperature span of magnetic refrigerator. The key component of the AMR system is a porous magnetic regenerator which allows a heat transfer medium (typically helium gas) to flow through it and therefore obviate intermittently operating an external heat switch. The AMR system alternatingly heats and cools the heat transfer medium by convection when the magneto-caloric effect is created under varying magnetic field. AMR may extend the temperature span for wider range than ADR (Adiabatic Demagnetization Refrigerator) at higher temperatures above 10K because magneto-caloric effects are typically concentrated in a small temperature range in usual magnetic refrigerants. The regenerative concept theoretically enables each magnetic refrigerant to experience a pseudo-Carnot magnetic refrigeration cycle in a wide temperature span if it is properly designed, although adequate thermodynamic matching of strongly temperature-dependent MCE (magneto-caloric effect) of the regenerator material and the heat capacity of fluid flow is often tricky due to inherent characteristics of magnetic materials. This paper covers historical developments, fundamental concepts, key components, applications, and recent research trends of AMR refrigerators for liquid helium or liquid hydrogen temperatures.

Development of a high-speed motor at extremely low temperatures with an axial self-bearing motor and a superconducting magnetic bearing

Superconducting technology has been significantly improved since the superconductor Y-Ba-Cu-O was discovered. This technology has been applied to many medical image-processing applications such as magnetoencephalogram (MEG) and magnetic resonance imaging (MRI). Because the superconducting phenomenon occurs at extremely low temperatures, liquid helium or liquid hydrogen is essential to obtain a low-temperature environment. In addition, it is well known that the decompression of the liquid helium creates superfluid helium. This phenomenon improves the performance of the superconducting devices. For that reason, a vacuum pump, which can be used at a cryostat, is required. In this paper, we propose a motor that has a small size and simple structure for use in the cryostat. The proposed motor consists of an axial self-bearing motor, superconducting magnetic bearings, and permanent-magnet repulsive-type passive magnetic bearings. The design of the motor and control method is introduced. The experimental results show that the proposed motor has a high possibility for high-speed rotation at extremely low temperatures.

Optical and near-infrared observations of SN 2011dh – The first 100 days

We present optical and near-infrared (NIR) photometry and spectroscopy of the Type IIb supernova (SN) 2011dh for the first 100 days. We complement our extensive dataset with SWIFT ultra-violet (UV) and Spitzer mid-infrared (MIR) data to build a UV to MIR bolometric lightcurve using both photometric and spectroscopic data. Hydrodynamical modelling of the SN based on this bolometric lightcurve have been presented in Bersten (2012). We find that the absorption minimum for the hydrogen lines is never seen below ~11000 km/s but approaches this value as the lines get weaker. This suggests that the interface between the helium core and hydrogen rich envelope is located near this velocity in agreement with the Bersten et al. (2012) He4R270 ejecta model. Spectral modelling of the hydrogen lines using this ejecta model supports the conclusion and we find a hydrogen mass of 0.01-0.04 solar masses to be consistent with the observed spectral evolution. We estimate that the photosphere reaches the helium core at 5-7 days whereas the helium lines appear between ~10 and ~15 days, close to the photosphere and then move outward in velocity until ~40 days. This suggests that increasing non-thermal excitation due to decreasing optical depth for the gamma-rays is driving the early evolution of these lines. We also provide and discuss pre- and post-explosion observations of the SN site which shows a reduction by 75 percent in flux at the position of the yellow supergiant coincident with SN 2011dh. The B, V and r band decline rates of 0.0073, 0.0090 and 0.0053 mag/day respectively are consistent with the remaining flux being emitted by the SN. Hence we find that the star was indeed the progenitor of SN 2011dh as previously suggested by Maund et al. (2011) and which is also consistent with the results from the hydrodynamical modelling.

Effect of Annealing on Magnetic Properties of Ultrafine Jet-Milled Nd-Fe-B Powders

This paper reports the effects of annealing on the magnetic properties of ultrafine Nd-Fe-B powders with an average particle size of 0.67 μm. The powder was fabricated from hydrogenation­disproportionation­desorption­recombination (HDDR)-treated Nd-Fe-B alloys by hydrogen decrepitation and helium jet milling. The coercivity of the ultrafine powders was slightly increased by annealing below 500°C, and was drastically increased by annealing above 600°C. These two stepwise increases in coercivity were attributed to hydrogen desorption and formation of a liquid Nd-rich phase. In addition, after annealing below 500°C, the coercivity (®0Hc) of the ultrafine powder was higher than that of the conventional powder, which was prepared from a strip-cast Nd-Fe-B alloy power with a particle size of 1.12 μm, because of a decrease in particle size. In contrast, after annealing above 600°C, the ®0Hc of the ultrafine powder was smaller than that of the conventional powder. The rare earth element content (Nd + Pr) was lower in the ultrafine powders than in the conventional powder. These results indicate that the rare earth element content was insufficient in the ultrafine powders. [doi:10.2320/matertrans.MAW201402]

α2(Zα)4mcontributions to the Lamb shift and the fine structure in light muonic atoms

Corrections to energy levels in light muonic atoms are investigated in order ${\ensuremath{\alpha}}^{2}(Z\ensuremath{\alpha}{)}^{4}m$. We pay attention to corrections which are specific for muonic atoms and include the electron vacuum polarization loop. In particular, we calculate relativistic and relativistic-recoil two-loop electron vacuum polarization contributions. The results are obtained for the levels with $n=1$, 2 and in particular for the Lamb shift ($2{p}_{1/2}\ensuremath{-}2{s}_{1/2}$) and fine-structure intervals ($2{p}_{3/2}\ensuremath{-}2{p}_{1/2}$) in muonic hydrogen, deuterium, and muonic helium ions.

Asteroseismology of the ZZ Ceti star KUV 11370+4222

KUV 11370+4222 is a ZZ Ceti star discovered in 1996, which has not been observed since then. We performed observations for KUV 11370+4222 in 2010 January. From the Fourier transform spectrum of the light curves, ten independent modes are detected. We searched for the best-fitting model by using the observed periods to match the model periods and get it with the total mass of 0.625 ${\rm M_{\odot}}$, the effective temperature of 10950 K, and the helium mass fraction and hydrogen mass fraction of $10^{-2.2}$ and $10^{-4.0}$, respectively. We have found a triplet of frequency split by rotation, which are $l=1$ modes. Using the frequency shifts we estimate a rotation period of $5.56\pm0.08$ h. Besides it, another $l=1$ mode is identified. The other observed periods are identified as $l=2$ modes. At last we investigated the property of the mode trapping.

Characterization of the SIDDHARTA-2 second level trigger detector prototype based on scintillators coupled to a prism reflector light guide

The SIDDHARTA experiment at the DAΦNE collider of LNF-INFN performed in 2009 high precision measurements of kaonic hydrogen and kaonic helium atomic transitions. To determine the K̄N isospin dependent scattering lenghts an important measurement, namely the kaonic deuterium one, is, however, still missing. Due to the very low expected yield of the kaonic deuterium Kα transition, a major improvement in the signal over background ratio is needed. To achieve a further background reduction, a second level trigger, based on the detection of charged pions produced by the K− absorption on various materials, including the target gas nuclei, is planned to be implemented in the future SIDDHARTA-2 experiment. For shielding-related geometrical limitations, a single side of the scintillators can be accessed; in order to reach a good time resolution and uniform efficiency, a both-end readout was then realized with complex multi-reflection light guides. In this work, the results of the tests made on a detector prototype, performed on the πM−1 beamline of the Paul Scherrer Institute (Switzerland), are presented. The tests had the goal to determine the efficiency and the time resolution for pions, which should comply with the minimum required values of 90% and 1 ns (FWHM) respectively. The obtained results, 96% efficiency and 750 ps FWHM for 170 MeV/c momentum pions, qualify the prototype as an excellent second level trigger for the SIDDHARTA-2 experiment. Similar results for 170 MeV/c momentum muons and electrons are also presented.

Isobaric expansion based regenerative trilateral thermal cycle with helium hydrogen and nitrogen as working fluids

The work aims feasible structures of regenerative trilateral thermal cycles (RTTC). The RTTC differs from the conventional quadrilateral Carnot based thermal cycles (Carnot, Otto, Diesel, Rankine, Brayton, Stirling, Ericsson, and variants of these cycles) in that the conversion of heat to mechanical work is performed during an isobaric expansion process, in which thermal energy absorption and conversion to mechanical work is simultaneously performed, contrary to what happens in conventional quadrilateral based Carnot engines.An analysis of the RTTC is carried out and results compared with that of a Carnot cycle operating under the same ratio of temperatures. Into the range of operating temperatures high thermal efficiency is achieved for hydrogen, helium and nitrogen as optional working fluids. These results combined with a cost effective and structural simple and compact engine open the way towards a new generation of power conversion engines.

Removal of the gadolinium interference from the measurement of selenium in human serum by use of collision cell quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS)

Measurement of selenium in serum is an important clinical biomarker of nutritional status. The presence of gadolinium (Gd) in samples following administration of the contrast agents used for magnetic resonance imaging (MRI) results in a significant positive bias when using quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). Three instrumental set-ups were assessed: standard mode with no collision gas and collision cell mode with either a hydrogen:helium mixture or hydrogen. The effect of Gd on the selenium (Se) signal was assessed using external quality assurance (EQA) specimens and internal quality control (IQC) materials, both unspiked and spiked with Gd. Serum previously shown to contain high concentrations of Gd-containing contrast agents were also analysed. Recoveries of Se in the spiked compared to the unspiked samples were: between 500% and 1300% using standard mode; 100% and 29,000% using collision cell mode with hydrogen:helium mixture; and between 99% and 103% using hydrogen. The use of H2 in the collision cell provided accurate results, indicating that the charge exchange reaction (CER) of Gd(2+) with H2 removes this interference. Analysis of patient serum known to contain the Gd contrast agent using the method gave results within the selenium reference range (adults 0.89-1.65 µmol/L). The presence of Gd, as low as 0.2 mg/L, in serum samples causes a positive interference on the measurement of Se by ICP-MS. Using a CER mode with pure H2 in the collision cell it was possible to fully remove the interference due to Gd(2+) from the signal for Se.

Methods of local interstellar medium investigation

The question of the Sun's motion relative to the local interstellar medium (LISM) is examined. Results from Russian, US, and French satellites and space probes observing scattered solar radiation in hydrogen Lyman-alpha and helium lines are presented. Data are briefly discussed on the direct registration inside the Solar System of neutral helium atoms, picked-up helium ions, and fast neutral hydrogen atoms entering from the LISM. The fast neutral hydrogen atoms arise in the region of solar wind–LISM interaction.

NON-RELATIVISTIC RADIATION MEDIATED SHOCK BREAKOUTS. III. SPECTRAL PROPERTIES OF SUPERNOVA SHOCK BREAKOUT

The spectrum of radiation emitted following shock breakout from a star's surface with a power-law density profile ρ∝xn is investigated. Assuming planar geometry, local Compton equilibrium, and bremsstrahlung emission as the dominant photon production mechanism, numerical solutions are obtained for the photon number density and temperature profiles as a function of time for hydrogen–helium envelopes. The temperature solutions are determined by the breakout shock velocity v0 and the pre-shock breakout density ρ0 and depend weakly on the value of n. Fitting formulae for the peak surface temperature at breakout as a function of v0 and ρ0 are provided, with , and the time dependence of the surface temperature is tabulated. The time integrated emitted spectrum is a robust prediction of the model, determined by and v0 alone and insensitive to details of light travel time or slight deviations from spherical symmetry. Adopting commonly assumed progenitor parameters, breakout luminosities of ≈1045 erg s−1 and ≈1044 erg s−1 in the 0.3–10 keV band are expected for blue supergiant (BSG) and red supergiant (RSG)/He-WR progenitors, respectively ( is well below the band for RSGs, unless their radius is ∼1013 cm). >30 detections of SN 1987A-like (BSG) breakouts are expected over the lifetime of ROSAT and XMM-Newton. An absence of such detections would imply either that the typical parameters assumed for BSG progenitors are grossly incorrect or that their envelopes are not hydrostatic. The observed spectrum and duration of XRF 080109/SN 2008D are in tension with a non-relativistic breakout from a stellar surface interpretation.

Deposition of YSZ Coatings in a Chamber at Pressures below 100 Pa Using Low-Power Plasma Spraying with an Internal Injection Powder Feeding

By decreasing the chamber pressure, the effective mean free path length in a plasma jet increases, resulting in a distinct decrease in the heat transfer from the plasma jet to the powder feedstock. Thus, instantaneous, complete melting or partial evaporation of the powders in the plasma jet becomes difficult. To create yttria partially stabilized zirconia coatings in a relatively low-power plasma jet and a low-pressure environment of 100 Pa, a new plasma torch with a specialized nozzle with an internal injection powder system was designed. Optical emission spectroscopy indicated that the feedstock powder could be partially vaporized in a 700-A plasma arc in either 40Ar–10H2 or 20Ar–20He–10H2 standard liters per minute (SLPM) plasma gas. Denser coatings were deposited at arc current of 700 A by changing the plasma gas mixture from argon–hydrogen to argon–helium–hydrogen. A compact coating was obtained as the amount of vaporized powder increased, but the microstructure of the coating lost its columnar morphology due to the limited amount of vapor phase. In addition, the porosity and microhardness of the coatings were measured.

Effects of hydrogen mixture into helium gas on deuterium removal from lithium titanate

Lithium titanate (Li2TiO3) pebbles were irradiated with deuterium ions with energy of 1.7keV and then exposed to helium or helium–hydrogen mixed gas at various temperatures, in order to evaluate the effects of gas exposure on deuterium removal from the pebbles. The amounts of residual deuterium in the pebbles were measured by thermal desorption spectroscopy. The mixing of hydrogen gas into helium gas enhanced the removal amount of deuterium. In other words, the amount of residual deuterium after the helium–hydrogen mixed gas exposure at lower temperature was lower than that after the helium gas exposure. In addition, we also evaluated the pebbles exposed to the helium gas with different hydrogen mixture ratio from 0% to 1%, at 573K. Although the amount of residual deuterium in the pebbles after the exposure decreased with increasing the hydrogen mixture ratio, the implanted deuterium partly remained after the exposure. These results suggest that the tritium inventory may occur at low temperature region in the blanket during the operation.

Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

An accurate determination of the immiscibility of helium in hydrogen has a direct impact on the understanding of the interior structure and of the evolution of Jovian planets. We extend our previous work on hydrogen-helium mixtures [Morales, Schwegler, Ceperley, Pierleoni, Hamel, and Caspersen, Proc. Natl. Acad. Sci. (USA) 106, 1324 (2009)] to lower pressures and lower temperatures, across the molecular dissociation regime in hydrogen to the low-pressure molecular liquid. Using density-functional-theory-based molecular dynamics together with thermodynamic integration techniques, we calculate the Gibbs free energy of the dense liquid as a function of pressure, temperature, and composition. We address the importance of the nonideal entropy of mixing in the solubility of helium in hydrogen and find that it is critically important in the molecular regime. The resulting demixing temperatures smoothly connect measurements done in diamond anvil cells to the high-temperature and -pressure conditions found in giant planet interiors.

First-Principles Study of the Elastic Properties of Hexagonal Phase ScA<sub>x</sub> (A=H, He)

First-principles calculations are performed to investigate the Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio of hexagonal phase ScAx(A=H, He), where x=0, 0.0313, 0.125 and 0.25, represent the ratio of interstitial atoms A (A=H, He) to Sc atoms. The influences of hydrogen concentrations and helium concentrations on elastic modulus and Poisson’s ratio of ScAx(A=H, He) have been studied. The results indicate that hydrogen and helium have different effects on the elastic modulus of hexagonal phase scandium. The change mechanism of the Poisson’s ratio with the variation of the x ranging from 0 to 0.25 has also been studied in hexagonal phase ScAx(A=H, He). In addition, the changes in the charge densities of ScAxdue to the presence of hydrogen and helium have been calculated.