Xe Ratios Research Articles

Global Ocean Cooling of 2.3°C During the Last Glacial Maximum

AbstractQuantitative constraints on past mean ocean temperature (MOT) critically inform our historical understanding of Earth's energy balance. A recently developed MOT proxy based on paleoatmospheric Xe, Kr, and N2 ratios in ice core air bubbles is a promising tool rooted in the temperature dependences of gas solubilities. However, these inert gases are systematically undersaturated in the modern ocean interior, and it remains unclear how air‐sea disequilibrium may have changed in the past. Here, we carry out 30 tracer‐enabled model simulations under varying circulation, sea ice cover, and wind stress regimes to evaluate air‐sea disequilibrium in the Last Glacial Maximum (LGM) ocean. We find that undersaturation of all three gases was likely reduced, primarily due to strengthened high‐latitude winds, biasing reconstructed MOT by −0.38 ± 0.37°C (1σ). Accounting for air‐sea disequilibrium, paleoatmospheric inert gases indicate that LGM MOT was 2.27 ± 0.46°C (1σ) colder than the pre‐industrial era.

Short-lived noble gas effluent trends from a research reactor

An understanding of anthropogenic sources of radioactive noble gases in the atmosphere is needed to enhance the discrimination ability of the International Monitoring System's sensors. These sources include commercial and research nuclear reactors and medical isotope production facilities. While abiding by local environmental ordinances these facilities all emit noble gas radioisotopes through normal operation. This research presents measurements and analysis of noble gas isotopes (41Ar, 135Xe, 135mXe, 137Xe, 138Xe, 87Kr, 88Kr, and 89Kr) made directly at the stack of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. The Xe and Kr noble gases are concurrently observed with 41Ar, a neutron activation product, when the reactor is operational. The magnitude of the Xe and Kr noble gases released is not constant over the HFIR cycle, but they temporally match the 41Ar trend. An isotope activity ratio analysis of these shorter lived isotopes combined with the observation of the cycle's temporal trend helps understand the noble gas production mechanism at the HFIR. Isotopes with short half-lives are not useful for long-range environmental monitoring. However, these measurements could potentially be combined with atmospheric modeling to predict the background source term of the longer-lived Xe ratios at a monitoring station.

Continuous Measurements of Dissolved Ne, Ar, Kr, and Xe Ratios with a Field-Deployable Gas Equilibration Mass Spectrometer.

Noble gases dissolved in natural waters are useful tracers for quantifying physical processes. Here, we describe a field-deployable gas equilibration mass spectrometer (GEMS) that provides continuous, real-time measurements of Ne, Ar, Kr, and Xe mole ratios in natural waters. Gas is equilibrated with a membrane contactor cartridge and measured with a quadrupole mass spectrometer, after in-line purification with reactive metal alloy getters. We use an electron energy of 35 V for Ne to eliminate isobaric interferences, and a higher electron energy for the other gases to improve sensitivity. The precision is 0.7% or better and 1.0% or better for all mole ratios when the instrument is installed in a temperature-controlled environment and a variable-temperature environment, respectively. In the lab, the accuracy is 0.9% or better for all gas ratios using air as the only calibration standard. In the field (and/or at greater levels of disequilbrium), the accuracy is 0.7% or better for Ne/Kr, Ne/Ar, and Ar/Kr, and 2.5% or better for Ne/Xe, Ar/Xe, and Kr/Xe using air as the only calibration standard. The field accuracy improves to 0.6% or better for Ne/Xe, Ar/Xe, and Kr/Xe when the data is calibrated using discrete water samples run on a laboratory-based mass spectrometer. The e-folding response time is 90-410 s. This instrument enables the collection of a large number of continuous, high-precision and accuracy noble gas measurements at substantially reduced cost and labor compared to traditional methods.

Comprehensive sets ofXe124(n,γ)Xe125andXe124(n,2n)Xe123cross-section data for assessment of inertial-confinement deuterium-tritium fusion plasma

The authors measure crucial neutron cross sections for ${}^{124}$Xe, a fusion dopant in deuterium-tritium capsules, with a predicted high neutron-capture rate. The data provides an accurate experimental basis to interpret measurements of the ${}^{125}$Xe/${}^{123}$Xe ratio, which is a sensitive diagnostic tool for the fuel density of the plasma in the capsules during the implosion.

17.4: Fluid Simulations and Experiments for Ultra‐Thin Shadow‐Mask PDP

AbstractAn ultra‐thin shadow mask plasma display panel is suitable for double‐sided display and 3D display. A self‐consistent fluid model is used to analyze the discharge characteristics of the ultra‐thin SMPDP cell. The discharge processes of ultra‐thin SMPDP and normal SMPDP are almost same proved by fluid model and ICCD images. Moreover, both the simulation and experimental results indicate that the discharge efficiency can be highly improved by using the ultra‐thin glass as dielectric layer for its 50‐70μm thick and 6.7 dielectric constant in ultra‐thin SMPDP compared to normal SMPDP especially in high Xe ratio.

Molecular Dynamics Simulation of Xe Behavior in U-Mo Alloys Fuel

Classical molecular dynamics simulations are used to investigate the fission gas Xe behavior in a U-Mo alloy fuel matrix. The embedded atom method potential proposed by Smirnova et al. is used to describe the U-Mo-Xe system. The results show that the initial configuration of interstitial Xe atoms in U-Mo alloys is very instable and has a strong tendency to get together and to form a Xe bubble by ejecting the adjacent U atoms and Mo atoms from their former normal lattice sites. The pressure in Xe bubbles is initially quite high and then drops with increasing Xe concentration obviously. The matrix swelling of U-Mo alloys associated with the Xe bubble growth follows approximately a linear relationship with the ratio of Xe to U at low Xe concentration while the rate of swelling increases rapidly at high Xe concentration. The simulation results are in good agreement with the experimental data. The recovery of the damaged structure in the U-Mo alloys matrix is also investigated. It is shown that a damaged structure cannot be recovered completely after a system is relaxed for a long time while still having lots of defects.

Heavy noble gases in solar wind delivered by Genesis mission

One of the major goals of the Genesis Mission was to refine our knowledge of the isotopic composition of the heavy noble gases in solar wind and, by inference, the Sun, which represents the initial composition of the solar system. This has now been achieved with permil precision: 36Ar/38Ar=5.5005±0.0040, 86Kr/84Kr=.3012±.0004, 83Kr/84Kr=.2034±.0002, 82Kr/84Kr=.2054 ± .0002, 80Kr/84Kr = .0412±.0002, 78Kr/84Kr=.00642±.00005, 136Xe/132Xe=.3001±.0006, 134Xe/132Xe=.3691±.0007, 131Xe/132Xe=.8256±.0012, 130Xe/132Xe=.1650±.0004, 129Xe/132Xe=1.0405±.0010, 128Xe/132Xe=.0842±.0003, 126Xe/132Xe=.00416±.00009, and 124Xe/132Xe=.00491±.00007 (error-weighted averages of all published data). The Kr and Xe ratios measured in the Genesis solar wind collectors generally agree with the less precise values obtained from lunar soils and breccias, which have accumulated solar wind over hundreds of millions of years, suggesting little if any temporal variability of the isotopic composition of solar wind krypton and xenon. The higher precision for the initial composition of the heavy noble gases in the solar system allows (1) to confirm that, exept 136Xe and 134Xe, the mathematically derived U–Xe is equivalent to Solar Wind Xe and (2) to provide an opportunity for better understanding the relationship between the starting composition and Xe-Q (and Q-Kr), the dominant current “planetary” component, and its host, the mysterious phase-Q.

Early differentiation and volatile accretion recorded in deep-mantle neon and xenon

The isotopes (129)Xe, produced from the radioactive decay of extinct (129)I, and (136)Xe, produced from extinct (244)Pu and extant (238)U, have provided important constraints on early mantle outgassing and volatile loss from Earth. The low ratios of radiogenic to non-radiogenic xenon ((129)Xe/(130)Xe) in ocean island basalts (OIBs) compared with mid-ocean-ridge basalts (MORBs) have been used as evidence for the existence of a relatively undegassed primitive deep-mantle reservoir. However, the low (129)Xe/(130)Xe ratios in OIBs have also been attributed to mixing between subducted atmospheric Xe and MORB Xe, which obviates the need for a less degassed deep-mantle reservoir. Here I present new noble gas (He, Ne, Ar, Xe) measurements from an Icelandic OIB that reveal differences in elemental abundances and (20)Ne/(22)Ne ratios between the Iceland mantle plume and the MORB source. These observations show that the lower (129)Xe/(130)Xe ratios in OIBs are due to a lower I/Xe ratio in the OIB mantle source and cannot be explained solely by mixing atmospheric Xe with MORB-type Xe. Because (129)I became extinct about 100 million years after the formation of the Solar System, OIB and MORB mantle sources must have differentiated by 4.45 billion years ago and subsequent mixing must have been limited. The Iceland plume source also has a higher proportion of Pu- to U-derived fission Xe, requiring the plume source to be less degassed than MORBs, a conclusion that is independent of noble gas concentrations and the partitioning behaviour of the noble gases with respect to their radiogenic parents. Overall, these results show that Earth's mantle accreted volatiles from at least two separate sources and that neither the Moon-forming impact nor 4.45 billion years of mantle convection has erased the signature of Earth's heterogeneous accretion and early differentiation.

7.3: Distinquished Paper: Ultra‐Thin Shadow‐Mask PDP Fabricated by Vacuum In‐line Sealing Technology

AbstractAn ultra‐thin shadow mask plasma display panel is put forward to meet the market demands of a much thinner, lighter and flexible display. Thanks to the ultra‐thin 70μm thick glass, a special vacuum in‐line sealing technology could be used to fabricate the novel device without a pumping tube. The sealed panel is only 300μm thick. The sealing characteristics and the discharge characteristics are investigated. The experimental results indicate that a high ratio of Xe in the gas mixture can be used, thereby improving the performance of the ultra‐thin SMPDP. In future applications AF32 type of foil glass will be used with a dielectric constant of 5.1. In addition a sealing temperature of 600 °C or higher will enable to exploit the full benefits of MgCaO protective layer. The ultra‐thin panel is well suited both for a double‐sided display and for 3D‐display.

81Kr‐Kr age and multiple cosmic‐ray exposure history of the Vaca Muerta mesosiderite

Abstract– Noble gas isotopic compositions were measured for a eucritic pebble and bulk material of a silicate–metal mixture from the Vaca Muerta mesosiderite as well as pyroxene and plagioclase separated from the eucritic pebble by total melting and stepwise heating methods. Trapped noble gases were degassed completely by a high‐temperature thermal event, probably at the formation of the Vaca Muerta parent body (VMPB). The presence of fissiogenic Xe isotopes from extinct 244Pu in the bulk samples might be a result of rapid cooling from an early high‐temperature metamorphism. High concentrations of cosmogenic noble gases enabled us to determine precise isotopic ratios of cosmogenic Kr and Xe. Spallogenic Ne from Na and unique Ar isotopic compositions were observed. The 81Kr‐Kr exposure age of 168 ± 8 Myr for the silicate pebble is distinctly longer than the age of 139 ± 8 Myr for the bulk samples. The precursor of the pebble had been irradiated on the surface of the VMPB for more than 60 Myr (first stage irradiation), with subsequent incorporation into bulk materials approximately 4 Gyr ago. The Vaca Muerta meteorite was excavated from the VMPB 140 Myr ago (second stage irradiation). Relative diffusion rates among the cosmogenic Ar, Kr, and Xe based on data obtained by stepwise heating indicate that Kr and Xe can be partially retained in pyroxene and plagioclase under the condition that resets the K‐Ar system. This result supports the presence of fission Xe and of excess concentration of cosmogenic Kr, which could have survived the thermal event approximately 3.8 Gyr ago.

Noble gas enrichments in porewater of estuarine sediments and their effect on the estimation of net denitrification rates

Abstract The concentration and the isotopic ratios of noble gases He, Ne, Ar, Kr and Xe were measured in porewater trapped in shallow sediments of the estuary of the St-Lawrence River, Quebec, Canada. The gases are atmospheric in origin but most samples have gas concentrations 1.7–28 times higher than those expected in solution in water at equilibrium with the atmosphere. Elemental fractionation of heavier noble gases Kr and Xe compared to Ar strongly suggests that noble gases were adsorbed on sediments or organic matter and then desorbed into porewaters due to depressurization, as collected samples were brought to the surface. Atmospheric Ar in porewater is used as a reference to measure the N2-fluxes at the water–sediment interface. Ignoring the Ar enrichments observed in porewater could lead to a severe underestimation of the denitrification rate in oceans and estuaries.

Geochemical constraints on the half-life ofTe130

To determine the half-life of {sup 130}Te we have analyzed multiple aliquots of geological telluride samples 100 times smaller than those previously reported using a unique resonance ionization mass spectrometer. We employ a low-fluence neutron irradiation that allows determination of parent and daughter from the same xenon isotopic analysis. Step heating of these irradiated samples allows the {sup 130}Xe/{sup 132}Xe ratio of fluids trapped inside the tellurides to be determined. Considering only samples where the trapped {sup 130}Xe/{sup 132}Xe ratio is demonstrably consistent with atmospheric xenon, we can avoid over- or under-estimating the half-life due to redistribution or inheritance of radiogenic {sup 130}Xe. Combining our work with literature data, it is clear that several relatively young samples have retained xenon quantitatively since formation, allowing the half-life to be determined as (8.0{+-}1.1)x10{sup 20} yr. Older samples have clearly been affected by post-formation processing. This suggests that there is little hope of monitoring solar luminosity through the geological record of {sup 126}Xe production by solar neutrinos, but it is possible that geologically useful chronological information can be obtained from this system.

Cosmic ray exposure age and time of formation of a new meteorite, Dhofar 007 achondrite from Oman: A rock fragment from the asteroid Vesta

The isotopic composition of noble gases was investigated in the Dhofar 007 meteorite. Petrographic and mineralogical observations suggested that it is a brecciated cumulate eucrite with high contents of siderophile elements. The concentrations of noble gases in Dhofar 007 are identical to those of other eucrites. Its cosmic ray exposure age was estimated as 11.8 ± 0.8 Ma, which coincides with a maximum on the histogram of comic ray exposure ages of eucrite meteorites. It can be supposed that, similar to other eucrites, Dhofar 007 was ejected from the surface of their parent body (presumably, asteroid Vesta) about 12.0 Ma ago. The crystallization age of the Dhofar 007 eucrite was estimated from the ratio of plutonogenic Xe to Nd as 4476 ± 22 Ma. The potassium-argon age is much younger, 3.7–4.1 Ga, which indicates partial loss of radiogenic argon during the history of the meteorite, most likely related to impact metamorphic events.

A New type of Xenon-Neon Barrier Discharge Fluorescent Lamps: Double Helical External Electrodes Lamp (DHEL)

Recently as interests in environmental issues increase, demands for mercury-free fluorescent lamps are increasing because mercury is harmful to human beings and creatures. As one of the solutions of this issue the authors have developed a new-type of mercury-free fluorescent lamps using double helical external electrodes. In this paper the fundamental characteristics of Xenon-Neon discharge in the Double Helical External Electrodes Lamps (DHEL) such as the luminance, power consumption and lamp current are investigated. When the pressure ratio of Xe: Ne was fixed at 7 : 3, total pressure at 1.33 kPa and external electrode pitch as 10 mm, luminance over 10000 cd / m2 is achieved. In addition as a prototype 1 m length DHEL is prepared and demonstrated to show basically there is no limit in length of DHEL.

Refining the noble gas record of the Réunion mantle plume source: Implications on mantle geochemistry

Abstract We report isotope analyses of helium, neon, argon, and xenon using different extraction techniques such as stepwise dynamic and static crushing, and high-resolution stepwise heating of three mantle xenoliths from Reunion Island. He and Ne isotopic compositions were similar to previously reported Reunion data, yielding a more radiogenic composition when compared to the Hawaiian or Icelandic mantle plume sources. We furthermore observed correlated 129 Xe/ 130 Xe and 136 Xe/ 130 Xe ratios following the mantle trend with maximum values of 6.93 ± 0.14 and 2.36 ± 0.06, respectively. High-resolution argon analyses resulted in maximum 40 Ar/ 36 Ar ratios of 9000–11,000, in agreement with maximum values obtained in previous studies. We observed a well-defined hyperbolic mixing curve between an atmospheric and a mantle component in a diagram of 40 Ar/ 36 Ar vs. 20 Ne/ 22 Ne. Using a mantle 20 Ne/ 22 Ne of 12.5 (Ne–B) a consistent 40 Ar/ 36 Ar value of 11,053 ± 220 in sample ILR 84-4 was obtained, whereas extrapolations to a higher mantle 20 Ne/ 22 Ne ratio of 13.8 (solar wind) would lead to a much higher 40 Ar/ 36 Ar ratio of 75,000, far above observed maximum values. This favours a mantle 20 Ne/ 22 Ne of about 12.5 considered to be equivalent to Ne–B. Extrapolated and estimated 40 Ar/ 36 Ar ratios of the Reunion, Iceland, Loihi, and MORB mantle sources, respectively, tend to be linearly correlated with air corrected 21 Ne/ 22 Ne and show the same systematic sequence of increasing relative contributions in radiogenic isotopes (Iceland–Loihi–Reunion–MORB) as observed for 4 He/ 3 He. In general, He–Ne–Ar isotope systematics of the oceanic mantle can be explained by following processes: (i) different degree of mixing between pure radiogenic and pure primordial isotopes generating the MORB and primitive plume (Loihi-type) endmembers; (ii) relatively recent fractionation of He relative to Ne and Ar, in one or both endmembers; (iii) after the primary fractionation event, different degrees of mixing between melts or fluids of MORB and primitive plume affinity generate the variety of observed OIB data, also on a local scale; (iv) very late-stage secondary fractionation during magma ascent and magma degassing leads to further strong variation in He/Ne and He/Ar ratios.

Multiphoton double ionization via field-independent resonant excitation.

The double ionization of xenon in the multiphoton regime has been studied at two wavelengths (0.77 and 0.79 microm) using an electron-ion coincidence technique and an intensity binned ion ratio method. Sharp resonant structures in the electron energy distribution correlated with the doubly charged ion, as well as a wavelength dependence of the Xe(2+)/Xe(+) ratio provides new insights. A mechanism involving the shelving of population in Rydberg states followed by excitation of a core electron is proposed.

Noble gases in ureilites: cosmogenic, radiogenic, and trapped components

Abundances and isotopic compositions of Ne (in bulk samples only), Ar, Kr, and Xe have been investigated in 6 monomict, 3 polymict, and the diamond-free ureilite ALH78019 and their acid-resistant, C-rich residues. Isotopic ratios of Kr and Xe are very uniform and agree with data for ureilites from the literature. The measured ratio 38Ar/36Ar showed large variations due to an experimental artifact. This is shown to be connected to the pressure dependence of the instrumental mass discrimination, which for ureilites with their low abundance of 40Ar is different from that of the usual air standard. This observation necessitates a reassessment for the recently reported 36Ar excesses due to possible decay of extinct 36Cl in the Efremovka meteorite.Trapped 22Ne in the range of (1.4–2.5) × 10−8 cc STP/g is present in bulk ureilites. A Ne three-isotope plot for polymict ureilites indicates the presence of solar Ne. 21Ne-based cosmic ray exposure ages for the 10 ureilites studied range from 0.1 Ma (for ALH78019) to 46.8 Ma (for EET83309)All ureilites may have started with nearly the same initial elemental ratio (132Xe/36Ar)0, established in the nebula during gas trapping into their carbon carrier phases (diamond, amorphous C) by ion implantation. Whereas diamonds are highly retentive, amorphous C has suffered gas loss due to parent body metamorphism. The correlation of the elemental ratios 132Xe/36Ar and 84Kr/36Ar along the mass fractionation line could be understood as a two-component mixture of the unaffected diamond gases and the fractionated (to varying degrees) gases from amorphous C. In this view, the initial ratio (132Xe/36Ar)0 is a measure of the plasma temperature in the nebula at the formation location of the carbon phases. Its lack of correlation with Δ17O (a signature of the silicate formation location) indicates that carbon phases and silicates formed independently in the nebula, and not from a carbon-rich magmaThe elemental ratios 132Xe/36Ar and 84Kr/36Ar in carbon-rich acid residues show a decreasing trend with depth (inferred from carbon consumption during combustion), which can be interpreted as a consequence of the ion implantation mechanism of gas trapping that leads to greater depth of implantation for lighter mass ionThe similarity between trapped gases in phase Q in primitive chondrites and the C phases in ureilites—for both elemental and isotopic compositions—strongly suggests that phase Q might also have received its noble gases by ion implantation from the nebula. The slight differences in the elemental ratios can be explained by a plasma temperature at the location of phase Q gas loading that was about 2000 K lower than for ureilite C phases. This inference is also consistent with the finding that the trapped ratio 129Xe/132Xe (1.042 ± 0.002) in phase Q is slightly higher, compared to that of ureilite C phases (1.035 ± 0.002), as a consequence of in situ decay of 129I, and becomes observable due to higher value of I/Xe in phase Q as a result of ion implantation at about 2000 K lower plasma temperature.

New electrode shape for high Xe‐content gas in AC PDP

One of the most important issues in AC PDP is the improvement of luminous efficiency. One possible method for achieving this aim is by increasing Xe partial pressure in discharge gas mixture. The increase of Xe ratio, however, causes the driving voltage to rise, even if brightness is increased. In this study, a new electrode shape is proposed. A test panel fabricated by using a new electrode shows that efficacy has improved by 25 % and sustain voltage has decreased by 20 % compared with the conventional structure.

Vacuum ultraviolet emission dynamics of a coplanar electrode microdischarge: dependence on voltage and Xe concentration

We report nanosecond time-resolved measurements of the vacuum ultraviolet (VUV) emission and current waveforms for a planar, surface-discharge plasma display electrode in Xe/Ne mixtures. The 173 nm excimer emission is separately resolved from the overall VUV emission by a removable fused silica filter. The time difference between the maximum of excimer emission and that of resonant atomic emission is measured at high Xe concentration. The decay time of the overall VUV emission decreases strongly as the Xe concentration increases due to three-body collisions leading to Xe2 formation. The decay time constants versus Xe concentration and pressure are measured and compared with published rate constants. The efficiency of VUV emission increases rapidly from 4% to 10% Xe, but only marginally with further increase to 30% Xe. For fixed Xe ratio, the VUV emission efficiency drops with increasing driving voltage.

Martian atmospheric and interior volatiles in the meteorite Nakhla

We report isotopic abundances of xenon, argon, and nitrogen for the observed distinct components in Martian meteorite Nakhla. In a stepwise release the 129Xe/132Xe ratios in the 800°C and 1000°C fractions show the signature of the modern atmosphere and other Xe ratios, when corrected for the cosmogenic component, confirm the isotopically fractionated modern atmospheric component. On the other hand, the Xe isotope ratios in the >1000°C steps reveal an isotopically unfractionated interior component, but with radiogenic 129Xe excesses. The isotopic composition of this interior component is consistent with Chass-S Xe (solar type), but is augmented by 244Pu-derived fission Xe. The fission components in interior trapped Xe (in both Nakhla and Chassigny) suggest that Mars effectively retained 244Pu-derived fission gas. A heavy (relative to interior N) nitrogen signature in the 600–900°C temperature steps also suggests a recent incorporation of Martian atmospheric gases. The N signatures in the high-temperature (>1000°C) steps are strongly affected by cosmic-ray-produced 15Nc and 36Ar and 38Ar abundances are dominated by the cosmogenic component. We discuss the signatures of Martian interior nitrogen and heavy noble gases and the constraints they provide on the evolutionary history of Mars.