Xenon Isotopes Research Articles

An exciting prospect: detecting inelastic transitions of xenon caused by dark matter

Dark matter can scatter and excite the xenon isotopes 129Xe and 131Xe to a low-lying excitation in a direct detection experiment. This signature is distinct from the canonical elastic scattering signal because the inelastic signal also contains the energy deposited from the subsequent prompt de-excitation of the nucleus. A measurement of the elastic and inelastic signal will allow a single experiment to distinguish between a spin-independent and spin-dependent interaction. In this paper, I will discuss the prospects of detecting this inelastic signal with up-coming tonne-scale two-phase xenon direct detection experiments.

Chondritic xenon in the Earth's mantle.

Noble gas isotopes are powerful tracers of the origins of planetary volatiles, and the accretion and evolution of the Earth. The compositions of magmatic gases provide insights into the evolution of the Earth's mantle and atmosphere. Despite recent analytical progress in the study of planetary materials and mantle-derived gases, the possible dual origin of the planetary gases in the mantle and the atmosphere remains unconstrained. Evidence relating to the relationship between the volatiles within our planet and the potential cosmochemical end-members is scarce. Here we show, using high-precision analysis of magmatic gas from the Eifel volcanic area (in Germany), that the light xenon isotopes identify a chondritic primordial component that differs from the precursor of atmospheric xenon. This is consistent with an asteroidal origin for the volatiles in the Earth's mantle, and indicates that the volatiles in the atmosphere and mantle originated from distinct cosmochemical sources. Furthermore, our data are consistent with the origin of Eifel magmatism being a deep mantle plume. The corresponding mantle source has been isolated from the convective mantle since about 4.45 billion years ago, in agreement with models that predict the early isolation of mantle domains. Xenon isotope systematics support a clear distinction between mid-ocean-ridge and continental or oceanic plume sources, with chemical heterogeneities dating back to the Earth's accretion. The deep reservoir now sampled by the Eifel gas had a lower volatile/refractory (iodine/plutonium) composition than the shallower mantle sampled by mid-ocean-ridge volcanism, highlighting the increasing contribution of volatile-rich material during the first tens of millions of years of terrestrial accretion.

Transverse spin relaxation and diffusion-constant measurements of spin-polarized 129Xe nuclei in the presence of a magnetic field gradient

The presence of a magnetic field gradient in a sample cell containing spin-polarized 129Xe atoms will cause an increased relaxation rate. We measured the transverse spin relaxation time of 129Xe verse the applied magnetic field gradient and the cell temperature. We then compared the different transverse spin relaxation behavior of dual isotopes of xenon (129Xe and 131Xe) due to magnetic field gradient in the same cell. The experiment results show the residual magnetic field gradient can be measured and compensated by applying a negative magnetic gradient in the sample cell. The transverse spin relaxation time of 129Xe could be increased 2–7 times longer when applying an appropriate magnetic field gradient. The experiment results can also be used to determine the diffusion constant of 129Xe in H2 and N2 to be 0.4 ± 0.26 cm2/sec and 0.12 ± 0.02 cm2/sec. The results are close with theoretical calculation.

Simultaneous detection of xenon and krypton in equine plasma by gas chromatography-tandem mass spectrometry for doping control.

Xenon can activate the hypoxia-inducible factors (HIFs). As such, it has been allegedly used in human sports for increasing erythropoiesis. Krypton, another noble gas with reported narcosis effect, can also be expected to be a potential and less expensive erythropoiesis stimulating agent. This has raised concern about the misuse of noble gases as doping agents in equine sports. The aim of the present study is to establish a method for the simultaneous detection of xenon and krypton in equine plasma for the purpose of doping control. Xenon- or krypton-fortified equine plasma samples were prepared according to reported protocols. The target noble gases were simultaneously detected by gas chromatography-triple quadrupole mass spectrometry using headspace injection. Three xenon isotopes at m/z 129, 131, and 132, and four krypton isotopes at m/z 82, 83, 84, and 86 were targeted in selected reaction monitoring mode (with the precursor ions and product ions at identical mass settings), allowing unambiguous identification of the target analytes. Limits of detection for xenon and krypton were about 19 pmol/mL and 98 pmol/mL, respectively. Precision for both analytes was less than 15%. The method has good specificity as background analyte signals were not observed in negative equine plasma samples (n = 73). Loss of analytes under different storage temperatures has also been evaluated. Copyright © 2016 John Wiley & Sons, Ltd.

International challenge to predict the impact of radioxenon releases from medical isotope production on a comprehensive nuclear test ban treaty sampling station

The International Monitoring System (IMS) is part of the verification regime for the Comprehensive Nuclear-Test-Ban-Treaty Organization (CTBTO). At entry-into-force, half of the 80 radionuclide stations will be able to measure concentrations of several radioactive xenon isotopes produced in nuclear explosions, and then the full network may be populated with xenon monitoring afterward. An understanding of natural and man-made radionuclide backgrounds can be used in accordance with the provisions of the treaty (such as event screening criteria in Annex 2 to the Protocol of the Treaty) for the effective implementation of the verification regime.Fission-based production of 99Mo for medical purposes also generates nuisance radioxenon isotopes that are usually vented to the atmosphere. One of the ways to account for the effect emissions from medical isotope production has on radionuclide samples from the IMS is to use stack monitoring data, if they are available, and atmospheric transport modeling. Recently, individuals from seven nations participated in a challenge exercise that used atmospheric transport modeling to predict the time-history of 133Xe concentration measurements at the IMS radionuclide station in Germany using stack monitoring data from a medical isotope production facility in Belgium. Participants received only stack monitoring data and used the atmospheric transport model and meteorological data of their choice.Some of the models predicted the highest measured concentrations quite well. A model comparison rank and ensemble analysis suggests that combining multiple models may provide more accurate predicted concentrations than any single model. None of the submissions based only on the stack monitoring data predicted the small measured concentrations very well. Modeling of sources by other nuclear facilities with smaller releases than medical isotope production facilities may be important in understanding how to discriminate those releases from releases from a nuclear explosion.

Determination of Atmospheric Krypton and Xenon by Gas Chromatography-Mass Spectrometry in Direct Injection Mode

Abstract Volume concentration determination of atmospheric krypton and xenon is very important for krypton-85 and radioactive xenon isotopes monitoring. An injection set-up integrated adjustable quantity sample injection and quantitative dilution function was designed. The effects of electron impact (EI) source parameters on the sensitivity of MS detector were studied. Optimal values were as follows: ionization energy of 70 eV, emission current of 40 mA, cathode voltage of 27 mV, ion focus voltage of 85 mV and lens compensation voltage of 20 V. A GC-MS method for the determination of krypton and xenon in atmosphere without sample pretreatment was developed. Minimal detected concentrations for krypton and xenon were 3.3 × 10−8 (V/V) and 2.6 × 10−9 (V/V) respectively. Moreover, krypton and xenon concentrations in the ground level air were measured with the results of 1.1 × 10−6 (V/V) and 9.3 × 10−8 (V/V). The related combined standard uncertainties for krypton and xenon results were 2.38% and 3.15%, respectively.

Sub-Doppler two-photon-excitation Rydberg spectroscopy of atomic xenon: mass-selective studies of isotopic and hyperfine structure

Mass-selective sub-Doppler two-photon excitation (TPE) spectroscopy is employed to resolve isotopic contributions for transitions to high-energy Rydberg levels of xenon in an atomic beam, using narrowband pulses of coherent ultraviolet light at 205–213 nm generated by nonlinear-optical conversion processes. Previous research (Kono et al 2013 J. Phys. B: At. Mol. Opt. Phys. 46 35401), has determined isotope energy shifts and hyperfine structure for 33 high-energy Rydberg levels of gas-phase xenon and accessed Rydberg levels at TPE energies in the range of 94 100–97 300 cm−1 with unprecedented spectroscopic resolution. The new isotopic-mass-resolved results were obtained by adding a pulsed free-jet atomic-beam source and a mass-selective time-of-flight detector to the apparatus in order to discern individual xenon isotopes and extract previously unresolved spectroscopic information. Resulting isotope energy shifts and hyperfine-coupling parameters are examined with regard to trends in principal quantum number n and in atomic angular-momentum quantum numbers, together with empirical and theoretical precedents for such trends.

Thermal neutrons registration by xenon gamma-ray detector

Experimental results of thermal neutrons detection by high pressure xenon gamma- ray spectrometers are presented. The study was performed with two devices with sensitive volumes of 0.2 and 2 litters filled with compressed mixture of xenon and hydrogen without neutron-capture additives. Spectra from Pu-Be neutron source were acquired using both detectors. Count rates of the most intensive prompt neutron-capture gamma-ray lines of xenon isotopes were calculated in order to estimate thermal neutrons efficiency registration for each spectrometer.

Analysis of fission gas release-to-birth ratio data from the AGR irradiations

A series of advanced gas reactor (AGR) irradiation tests is being conducted in the advanced test reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tristructural isotropic (TRISO) fuel used in the High temperature gas-cooled reactor (HTGR). Each AGR test consists of multiple independent capsules containing fuel compacts placed in a graphite cylinder shrouded by a steel shell. These capsules are instrumented with thermocouples (TC) embedded in the graphite enabling temperature control. For AGR-1, the first US irradiation of modern TRISO fuel completed in 2009, there were no particle failures detected. For AGR-2, a few exposed kernels existed in the fuel compacts based upon quality control data. For the AGR-3/4 experiment, particle failures in all capsules were expected because of the use of designed-to-fail (DTF) fuel particles whose kernels are identical to the driver fuel kernels and whose coatings are designed to fail under irradiation. The release-rate-to-birth-rate ratio (R/B) for each of krypton and xenon isotopes is calculated from release rates measured by the germanium detectors used in the AGR fission product monitoring (FPM) system installed downstream from each irradiated capsule. Birth rates are calculated based on the fission power in the experiment and fission product generation models. Thus, this R/B is a measure of the ability of fuel particle coating layers and compact matrix to retain fission gas atoms preventing their release into the sweep gas flow. The major factors that govern gaseous diffusion and release processes are found to be fuel material diffusion coefficient, temperature, and isotopic decay constant. To compare the release behavior among the AGR capsules and historic experiments, the R/B per failed particle is used. HTGR designers use this parameter in their fission product behavior models. For the U.S. TRISO fuel, a regression analysis is performed to establish functional relationships between R/B per failed particle of selected noble gas isotopes and temperature. The effect of isotopic half-life is also obtained from the data. To reduce measurement uncertainty of the release rate, the krypton and xenon isotopes selected for regression analysis have a short enough half-life to achieve equilibrium in the capsule, but are also long enough to provide a measurable signal in the FPM detector. The impact of uncertainty of the estimated number of failed particles in each capsule is also examined. This study found that R/B values for AGR test fuel are comparable to R/B obtained in historic tests. The correlation with isotopic half-life is very stable with time indicating no strong influence of burnup on release. The correlation can be used by reactor designers to estimate fission gas release from postulated failed fuel in HTGR cores.

Cosmochemical and spectroscopic properties of Northwest Africa 7325—A consortium study

AbstractThis work is part of a project to build an infrared database in order to link IR data of planetary materials (and therefore possible Mercury material) with remote sensing observations of Mercury, which will probably be obtained by the MERTIS instrument on the forthcoming BepiColombo mission.The unique achondrite Northwest Africa (NWA) 7325, which has previously been suggested to represent the first sample from Mercury, was investigated by optical and electron microscopy, and infrared and Raman spectroscopy. In addition, the oxygen, strontium, xenon, and argon isotopes were measured and the abundance of selected trace elements determined. The meteorite is a cumulate rock with subchondritic abundances of HFSE and REE and elevated Sr contents, which underwent a second heating and partial remelting process. Oxygen isotope measurements show that NWA 7325 plots in the ureilite field, close to the ALM‐A trachyandesitic fragment found in the unique Almahata Sitta meteorite breccia. On the other hand, mineralogical investigations of the pyroxenes in NWA 7325 provide evidence for similarities to the lodranites and acapulcoites. Furthermore, the rock is weakly shocked and argon isotope data record ancient (~4.5 Ga) plateau ages that have not been reset. The sample records a cosmogenic exposure age of ~19 Ma. Systematics of Rb‐Sr indicate an extreme early volatile depletion of the precursor material, similar to many other achondrite groups. However, despite its compositional similarities to other meteorite groups, our results suggest that this meteorite is unique and unrelated to any other known achondrite group. An origin for NWA 7325 as a sample from the planet Mercury is not supported by the results of our investigation. In particular, the evidence from infrared spectroscopy indicates that a direct relationship between NWA 7325 and the planet Mercury can be ruled out: no acceptable spectral match between laboratory analyses and remote sensing observations from Mercury has been obtained. However, we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions.

Calibration of low-level beta-gamma coincidence detector systems for xenon isotope detection

The beta-gamma coincidence detector systems used for the measurement of the CTBT-relevant xenon isotopes (Xe-131m, Xe-133m, Xe-133 and Xe-135) in the International Monitoring System network and in the On-Site Inspection are reviewed. These detectors typically consist of a well-type or bore-through NaI crystal into which a measurement cell, serving also as a sample container, is inserted. This work describes the current calibration procedure for energy, resolution and efficiency, implementation challenges, availability and uncertainties of the specific nuclear decay data and the path forward to full calibration validation using GEANT4.

Error tolerance studies for the superconducting linac of RAON

RAON, an ion accelerator, is planned in Daejeon, Korea, by the Rare Isotope Science Project. RAON has three linear accelerators, and they will accelerate various stable ions such as uranium, xenon, oxygen and rare isotopes from the isotopes separation on-line system. The linear accelerators of the RAON adopted superconducting cavities and a warm quadrupole doublet structure. Because the target beam power is 400 kWfor the uranium beam, the small beam loss in the linear accelerators can be concluded to the radiation damage to the devices in this region. As a result, estimating the allowable alignment and radio-frequency errors for the RAON linear accelerator is one of the important topics for this project. In this paper, the beam dynamics simulation results, including such errors, will be described.

Radioxenon spiked air

Four of the radioactive xenon isotopes (131mXe, 133mXe, 133Xe and 135Xe) with half-lives ranging from 9 h to 12 days are produced from nuclear fission and can be detected from days to weeks following their production and release. Being inert gases, they are readily transported through the atmosphere. Sources for release of radioactive xenon isotopes include operating nuclear reactors via leaks in fuel rods, medical isotope production facilities, and nuclear weapons' detonations. They are not normally released from fuel reprocessing due to the short half-lives. The Comprehensive Nuclear-Test-Ban Treaty has led to creation of the International Monitoring System. The International Monitoring System, when fully implemented, will consist of one component with 40 stations monitoring radioactive xenon around the globe. Monitoring these radioactive xenon isotopes is important to the Comprehensive Nuclear-Test-Ban Treaty in determining whether a seismically detected event is or is not a nuclear detonation. A variety of radioactive xenon quality control check standards, quantitatively spiked into various gas matrices, could be used to demonstrate that these stations are operating on the same basis in order to bolster defensibility of data across the International Monitoring System. This paper focuses on Idaho National Laboratory's capability to produce three of the xenon isotopes in pure form and the use of the four xenon isotopes in various combinations to produce radioactive xenon spiked air samples that could be subsequently distributed to participating facilities.

Source term estimates of radioxenon released from the BaTek medical isotope production facility using external measured air concentrations

BATAN Teknologi (BaTek) operates an isotope production facility in Serpong, Indonesia that supplies 99mTc for use in medical procedures. Atmospheric releases of 133Xe in the production process at BaTek are known to influence the measurements taken at the closest stations of the radionuclide network of the International Monitoring System (IMS). The purpose of the IMS is to detect evidence of nuclear explosions, including atmospheric releases of radionuclides. The major xenon isotopes released from BaTek are also produced in a nuclear explosion, but the isotopic ratios are different. Knowledge of the magnitude of releases from the isotope production facility helps inform analysts trying to decide if a specific measurement result could have originated from a nuclear explosion. A stack monitor deployed at BaTek in 2013 measured releases to the atmosphere for several isotopes. The facility operates on a weekly cycle, and the stack data for June 15–21, 2013 show a release of 1.84 × 1013 Bq of 133Xe. Concentrations of 133Xe in the air are available at the same time from a xenon sampler located 14 km from BaTek. An optimization process using atmospheric transport modeling and the sampler air concentrations produced a release estimate of 1.88 × 1013 Bq. The same optimization process yielded a release estimate of 1.70 × 1013 Bq for a different week in 2012. The stack release value and the two optimized estimates are all within 10% of each other. Unpublished production data and the release estimate from June 2013 yield a rough annual release estimate of 8 × 1014 Bq of 133Xe in 2014. These multiple lines of evidence cross-validate the stack release estimates and the release estimates based on atmospheric samplers.

Xenon isotopes in the MORB source, not distinctive of early global degassing

AbstractAlthough fissiogenic Xe in mid‐ocean ridge basalt (MORB) has long been used inferred to infer an early (>4 Ga) catastrophic mantle degassing, decomposition of the analyzed gas in terms of its constituents requires several assumptions. The canonical interpretation has not been tested using the full spectrum of possible initial components and radiogenic inputs. We use a Markov chain Monte Carlo approach that examines a broad range of Xe isotopic components present during Earth formation and evolution. Our best fit simulations are consistent with the preservation of much higher Pu/U in MORB source Xe than previously recognized but are equally supportive of both limited and early catastrophic loss. We show that an initially Xe depleted upper mantle that becomes progressively ingassed through both radiogenic ingrowth and subduction of evolving atmospheric Xe is equally consistent with all evidence, underscoring the need for improvements to our knowledge of fission Xe spectra, MORB Xe measurements, and Pu geochemistry.

The evolution of MORB and plume mantle volatile budgets: Constraints from fission Xe isotopes in Southwest Indian Ridge basalts

We present high-precision measurements of the fission isotopes of xenon (Xe) in basalts from the Southwest Indian Ridge (SWIR) between 16°E and 25°E. Corrections for syn- to post-eruptive atmospheric contamination yield the Xe isotopic compositions of SWIR mantle sources. We solve for the proportions of mantle Xe derived from the primordial mantle Xe budget, recycling of atmospheric Xe, decay of short-lived 129I, fission of extinct 244Pu, and fission of extant 238U. Xe isotope systematics evident in SWIR basalts and other mantle-derived samples provide new insights into the integrated history of mantle source degassing and regassing. We find that recycled atmospheric Xe dominates the Xe inventories of the SWIR Western and Eastern Orthogonal Supersegment mantle sources (∼80–90% of 132Xe is recycled in origin), consistent with results from studies of plume-influenced basalts from Iceland and the Rochambeau Rift. While significant regassing of the mantle is evident, we also find differences in the extent of degassing of the MORB and plume sources. MORB sources are consistently characterized by a lower fraction of fission Xe derived from Pu-fission, indicating a greater extent of degassing relative to the plume source. The prevalence of recycled atmospheric Xe in mantle sources indicates incorporation of depleted recycled material even into mantle sources with primitive He and Ne isotopic compositions. Consequently, depleted lithophile isotopic compositions in mantle sources with primitive He and Ne cannot be interpreted as evidence for a nonchondritic bulk silicate Earth.

Inelastic neutron scattering studies of132,134Xe: Elucidating structure in a transitional region and possible interferences for 0vββsearches

Highly enriched (> 99.9%) 132 Xe and 134 Xe gases were converted to solid 132 XeF2 and 134 XeF2 and were used as scattering samples for inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory (UKAL). Lifetimes of levels up to 3.5 MeV in excitation energy in these xenon isotopes were measured using the Doppler-shift attenuation method, allowing the determination of reduced transition probabilities. Gamma rays corresponding to new transitions and levels have been observed. In particular, tentative new excited 0 + states and associated decays have been examined in an effort to elucidate the structure of these nuclei in a transitional region, and comparisons have been drawn with models which seek to describe such nuclei, e.g., the E(5) critical-point symmetry of the IBM. Newly identified potential interferences for neutrinoless double-beta decay searches involving 136 Xe are also discussed.

Investigation of dipole strength up to the neutron separation energy atγELBE

The bremsstrahlung facility at the ELBE accelerator offers the possibility to investigate dipole strength distributions up to the neutron-separation energies with photon up to 16 MeV in energy. The facil- ity and various results for nuclides measured during recent years are presented. One example is the study of the N = 80 nuclide 136 Ba. The other presented example is the study of the chain of xenon isotopes from N = 70 to N = 80 which aimed to investigate the influence of nuclear deformation an neutron excess on the dipole strength in the pygmy region. An overview of the analysis is given. GEANT4 simulations were performed to determine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasi-continuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground- state transitions are compared with theoretical predictions and results within the chain of isotopes. With the help of the measured dipole distribution it is possible to describe gamma-ray spectra following neutron capture more precisely.

Urine analysis concerning xenon for doping control purposes.

On September 1(st) 2014, a modified Prohibited List as established by the World Anti-Doping Agency (WADA) became effective featuring xenon as a banned substance categorized as hypoxia-inducible factor (HIF) activator. Consequently, the analysis of xenon from commonly provided doping control specimens such as blood and urine is desirable, and first data on the determination of xenon from urine in the context of human sports drug testing, are presented. In accordance to earlier studies utilizing plasma as doping control matrix, urine was enriched to saturation with xenon, sequentially diluted, and the target analyte was detected as supported by the internal standard d6 -cyclohexanone by means of gas chromatography/triple quadrupole mass spectrometry (GC/MS/MS) using headspace injection. Three major xenon isotopes at m/z 128.9, 130.9 and 131.9 were targeted in (pseudo) selected reaction monitoring mode enabling the unambiguous identification of the prohibited substance. Assay characteristics including limit of detection (LOD), intraday/interday precision, and specificity as well as analyte recovery under different storage conditions were determined. Proof-of-concept data were generated by applying the established method to urine samples collected from five patients before, during and after (up to 48 h) xenon-based general anesthesia. Xenon was traceable in enriched human urine samples down to the detection limit of approximately 0.5 nmol/mL. The intraday and interday imprecision values of the method were found below 25%, and specificity was demonstrated by analyzing 20 different blank urine samples that corroborated the fitness-for-purpose of the analytical approach to unequivocally detect xenon at non-physiological concentrations in human urine. The patients' urine specimens returned 'xenon-positive' test results up to 40 h post-anesthesia, indicating the limits of the expected doping control detection window. Since xenon has been considered a prohibited substance according to WADA regulations in September 2014, its analysis from common specimens of routine sports drug testing is desirable. In previous studies, its traceability in whole blood and plasma was shown, and herein a complementary approach utilizing doping control urine samples for the GC/MS/MS analysis of xenon was reported.

The iodine-plutonium-xenon age of the Moon-Earth system revisited.

Iodine-plutonium-xenon isotope systematics have been used to re-evaluate time constraints on the early evolution of the Earth-atmosphere system and, by inference, on the Moon-forming event. Two extinct radionuclides ((129)I, T1/2=15.6 Ma and (244)Pu, T1/2=80 Ma) have produced radiogenic (129)Xe and fissiogenic (131-136)Xe, respectively, within the Earth, the related isotope fingerprints of which are seen in the compositions of mantle and atmospheric Xe. Recent studies of Archaean rocks suggest that xenon atoms have been lost from the Earth's atmosphere and isotopically fractionated during long periods of geological time, until at least the end of the Archaean eon. Here, we build a model that takes into account these results. Correction for Xe loss permits the computation of new closure ages for the Earth's atmosphere that are in agreement with those computed for mantle Xe. The corrected Xe formation interval for the Earth-atmosphere system is [Formula: see text] Ma after the beginning of Solar System formation. This time interval may represent a lower limit for the age of the Moon-forming impact.