ArticlePDF Available

Krypton Separation from Ambient Air for Application in Collinear Fast Beam Laser Spectroscopy

Authors:
  • Laser Institute for Research and Applications LIRA, Beni - Suef University Egypt

Abstract and Figures

A portable apparatus for the separation of krypton from environmental air samples was tested. The apparatus is based on the cryogenic trapping of gases at liquid nitrogen temperature followed by controlled releases at higher temperatures. The setup consists of a liquid nitrogen trap for the removal of H(2)O and CO(2), followed by charcoal-filled coils that sequentially collect and release krypton and other gases providing four stages of gas chromatography to achieve separation and purification of krypton from mainly N(2), O(2), and Ar. Residual reactive gases remaining after the final stage of chromatography are removed with a hot Ti sponge getter. A thermal conductivity detector is used to monitor the characteristic elution times of the various components of condensed gases in the traps during step-wise warming of the traps from liquid nitrogen temperatures to 0 °C, and then to 100 °C. This allows optimizing the switching times of the valves between the stages of gas chromatography so that mainly krypton is selected and loaded to the next stage while exhausting the other gases using a He carrier. A krypton separation efficiency of ~80 % was determined using a quadrupole mass spectrometer.
Content may be subject to copyright.
A preview of the PDF is not available
Conference Paper
This paper expounds the important application of titanium sponge adsorption in inert gas purification, the reaction mechanism of titanium with nitrogen and oxygen was introduced. Explored the relationship between the absorption capacity of sponge titanium on the active gas in air samples and the gas flow rate. The model of sponge titanium for flowing air absorption was established by data analysis. The designed experiment verified the relationship between the titanium processing capacity and the gas collecting device. Finally, the influence of the mass of the sponge titanium on the degassing capacity was studied through experiments.
Article
Current and foreseen population growths will lead to an increased demand in freshwater, large quantities of which is stored as groundwater. The ventilation age is crucial to the assessment of groundwater resources, complementing the hydrological model approach based on hydrogeological parameters. Ultra-trace radioactive isotopes of Kr ( Kr and Kr) possess the ideal physical and chemical properties for groundwater dating. The recent advent of atom trap trace analyses (ATTA) has enabled determination of ultra-trace noble gas radioisotope abundances using 5-10 L of pure Kr. Anticipated developments will enable ATTA to analyze radiokrypton isotope abundances at high sample throughput, which necessitates simple and efficient sample preparation techniques that are adaptable to various sample chemistries. Recent developments of field gas extraction devices and simple and rapid Kr separation method at the University of Chicago are presented herein. Two field gas extraction devices optimized for different sampling conditions were recently designed and constructed, aiming at operational simplicity and portability. A newly developed Kr purification system enriches Kr by flowing a sample gas through a moderately cooled (138 K) activated charcoal column, followed by a gentle fractionating desorption. This simple process uses a single adsorbent and separates 99% of the bulk atmospheric gases from Kr without significant loss. The subsequent two stages of gas chromatographic separation and a hot Ti sponge getter further purify the Kr-enriched gas. Abundant CH4 necessitates multiple passages through one of the gas chromatographic separation columns. The presented Kr separation system has a demonstrated capability of extracting Kr with 90% yield and 99% purity within 75 minutes from 1.2 to 26.8 L STP of atmospheric air with various concentrations of CH4. The apparatuses have successfully been deployed for sampling in the field and purification of groundwater samples.
Article
Radioactive noble-gas isotopes,85Kr (half-life t1/2=10.8 y), 39Ar (t1/2=269 y), and 81Kr (t1/2=229,000 y), are ideal tracers and can be detected by atom trap trace analysis (ATTA), a laser-based technique, from environmental samples like air and groundwater. Prior to ATTA measurements, it is necessary to efficiently extract krypton and argon gases from samples. Using a combination of cryogenic distillation, titaniumchemical reaction and gas chromatography, we demonstrate that we can recover both krypton and argon gases from 1–10 L “air-like” samples with yields in excess of 90% and 98%, respectively, which meet well the requirements for ATTA measurements. A group of testing samples are analyzed to verify the performance of the system, including two groundwater samples obtained from north China plain.
Article
Long-lived radioactive krypton isotopes, 81Kr (t_1/2=229,000yr) and 85Kr (t_1/2=10.76yr), are ideal tracers. 81Kr is cosmogenic, and can be used for dating groundwater beyond the 14C age. 85Kr is a fission product, and can be applied in atmospheric studies, nuclear safety inspections, and dating young groundwater. It has long been a challenge to analyze radio-krypton in small samples, in which the total number of such isotopes can be as low as 1X10^5. This work presents a system developed to analyze 81Kr and 85Kr from a few liters of air samples. A separation system based on cryogenic distillation and gas-chromatographic separation is used to extract krypton gas with an efficiency of over 90% from air samples of 1 - 50 L. 85Kr/Kr and 81Kr/Kr ratios in krypton gases are determined from single atom counting using a laser-based atom trap. In order to test the performance of the system, we have analyzed various samples collected from ambient air and extracted from groundwater, with a minimum size of 1 liter. The system can be applied to analyze 81Kr and 85Kr in environmental samples including air, groundwater and ices.
Article
Full-text available
A fast non-radiometric technique for ultratrace analysis of the radioisotopes 29Sr and 90Sr in environmental samples has been developed by combining mass separation with collinear laser resonance ionization spectrometry. The efficiency and isotopic selectivity of this method allows the determination of 3 × 106 atoms of 90Sr and 1 × 108 atoms of 89Sr in the presence of 1017 atoms of stable strontium, corresponding to an overall efficiency of better than 10-5 and a suppression of stable strontium of more than 1010. Simple and fast chemical separation procedures in combination with this technique enable the accurate determination of 89,90Sr activity in various types of environmental samples within one day, which is important in case of an emergency. The results for different environmental and technical samples, including air filters, soil, grass and milk as well as cooling water from a nuclear power station, are presented, indicating the potential and versatility of this technique.
Article
Full-text available
A novel scheme of coUinear fast beam laser spectroscopy for the detection of the long lived rare isotope *^Kr by observing the optical hyperfme structure spectrum is presented. The technique utilizes cascade two-step excitation to pump metastable krypton atoms to a high-lying Rydberg level. The present work on krypton was motivated by the fact that *^ Kr is a major tracer gas for exploring the reservoir structure of large oil fields. *^Kr detection in ambient air is also of importance for monitoring nuclear activities on a world wide scale. The technique has been successfully applied to stable krypton isotopes and to^^Kr. The selectivity is at the one part in lO'" level and the sensitivity at a few hundred ions/s.
Article
The isotope shifts and hyperfine-structure-splitting constants of the 6s21S0-5d6p 3D1 (λ=538.2 nm) and 5d23P2-5d6p 1D2 (λ=548.4 nm) transitions of La II have been measured by collinear laser-ion-beam spectroscopy for the accelerator-produced isotopes 135La and 137La, and for the naturally occurring isotopes 138La and 139La. The magnetic moments of the ground states of the isotopes 135La and 137La have been determined to be μ(135)= +3.70(9)μN and μ(137)=+2.700(15)μN, respectively, and the quadrupole moments to be Q(135) =-0.4(4) e b and Q(137)=+0.21(3) e b. The ratio of the magnetic dipole coupling constants A(138)/A(139) of the level 5d6p 3D 1 has shown a -0.35(23)% hyperfine anomaly with respect to the NMR ratio of the nuclear g factors. The change in the mean-square nuclear charge radius determined from the isotope shift between 139La and 135La is δ〈r2〉135,139=0.08(3) fm2. This value is smaller than the predictions made by the finite-range droplet model or by the Hartree-Fock plus BCS calculation.
Article
A new, highly sensitive method of laser spectroscopy of atoms and molecules based on multiple photon ionization is described. The history, characteristics and some key applications of this method are presented.
Article
Applications of accelerator mass spectrometry (AMS) evolved into multi-disciplinary research covering virtually every domain of our environment at large. The possibilities of applications are clearly coupled to technical developments of AMS, which will be covered by the accompanying article of H.-A. Synal. The present review therefore concentrates on describing AMS applications to the largest extent possible. Since the knowledge of the author on the many fields where AMS measurements are performed is, of course, limited, the selection of examples discussed in this review is somewhat biased. In order to compensate for this, a rather long list of references is presented, which should be consulted for a deeper understanding of the respective fields. The seven domains of our environment at large (atmosphere, biosphere, hydrosphere, cryosphere, lithosphere, cosmosphere, and technosphere) are being used as a guideline for the present review.
Article
A brief review of the current status of Accelerator Mass Spectrometry is presented, with emphasis on some of the most recent technical developments.