Separation Of Xenon Research Articles

A new automated method for measuring noble gases and their isotopic ratios in water samples

A method is presented for precisely measuring all five noble gases and their isotopic ratios in water samples using multiple programmed multistage cryogenic traps in conjunction with quadrupole mass spectrometry and magnetic sector mass spectrometry. Multiple automated cryogenic traps, including a two‐stage cryotrap used for removal of water vapor, an activated charcoal cryotrap used for helium separation, and a stainless steel cryotrap used for neon, argon, krypton, and xenon separation, allow reproducible gas purification and separation. The precision of this method for gas standards is ±0.10% for He, ±0.14% for Ne, ±0.10% for Ar, ±0.14% for Kr, and ±0.17% for Xe. The precision of the isotopic ratios of the noble gases in gas standards are ±1.9‰ for 20Ne/22Ne, ±2.0‰ for 84Kr/86Kr, ±2.5‰ for 84Kr/82Kr, ±0.9‰ for 132Xe/129Xe, and ±1.3‰ for 132Xe/136Xe. The precision of this method for water samples, determined by measurement of duplicate pairs, is ±1% for He, ±0.9% for Ne, ±0.3% for Ar, ±0.3% for Kr, and ±0.2% for Xe. An attached magnetic sector mass spectrometer measures 3He/4He with precisions of ±0.1% for air standards and ±0.14% for water samples.

Re-engineering Xen internals for higher-assurance security

The Xenon project is investigating the construction of a higher-assurance open source separation kernel based on the Xen open source hypervisor. Just as the Xen open source hypervisor was initially developed from the open source Linux operating system, by simplifying Linux and modifying its design, the Xenon separation kernel is being developed from Xen. The primary goal of the Xenon project is to investigate issues in creating an open source software product with higher security assurance than conventional open source software. The Xenon project is also focused on (1) problems relating to separation kernels that support unmodified uninterpreted commercial off the shelf (COTS) guests and (2) distinctions between these kinds of separation kernels and hypervisors. This paper explains the Xenon project's approach to re-engineering Xen's internal structure into a higher-assurance form. If conventional open source software cannot be brought into this form with moderate amounts of re-engineering then higher-assurance open source software is probably not practical. Our results indicate that moderate amounts of re-engineering will be sufficient for all but a small part of the code. The remaining code is small enough to be addressed in a reasonable time, even though more effort is required.

A chromatographic system for removal of radioactive 85Kr from xenon

Extremely low count rates of useful events in detectors of neutrino or weakly interacting exotic particles require using detector working media with low levels of radioactive contaminants. Liquid xenon, highly purified and filtered using advanced semiconductor industry technologies serves as an attractive target for several modern experiments searching for cold dark matter, double beta decay, and detection of low energy neutrino. Separation of xenon from trace amounts of 85Kr cannot be achieved with commercially available gas purifiers. We have developed an automated system for purification of xenon from trace amounts of krypton. The system has been used to purify 25 kg of xenon to the level of < 3 ppt of krypton. The purified xenon will be used for the two-phase emission detector, XENON10, to search for WIMP dark matter in the Gran Sasso Underground Laboratory.

Production of nitrogen-free, hyperpolarized 129 Xe gas

Xe with a nuclear polarization far above the thermal equilibrium value (hyperpolarized) is used in NMR studies to increase sensitivity. Gaseous, adsorbed, or dissolved xenon is utilized in physical, chemical, and medical applications. With the aim in mind to study single-crystal surfaces by NMR of adsorbed hyperpolarized 129Xe, three problems have to be solved. The reliable production of 129Xe with highest nuclear polarization possible, the separation of the xenon gas from the necessary quench gas nitrogen without polarization loss, and the dosing/delivery of small amounts of polarized xenon gas to a sample surface. Here we describe an optical pumping setup that regularly produces xenon gas with a 129Xe nuclear polarization of 0.7(±0.07). We show that a freeze–pump–thaw separation of xenon and nitrogen is feasible without a significant loss in xenon polarization. The nitrogen partial pressure can be suppressed by a factor of 400 in a single separation cycle. Dosing is achieved by using the low vapor pressure of a frozen hyperpolarized xenon sample.

Plutonium-244 fission xenon and primordial xenon in lunar samples and meteorites

Xenon found in lunar samples is a binary mixture of244Pu fission xenon and a trapped xenon, whose isotopic composition often shows a striking resemblance to that ofTakaoka's1 primitive xenon. The decay product of129I is conspicuously absent in lunar samples and this may be attributed to the facts that (a) the half-life of129I is much shorter than that of244Pu, and (b) the separation of xenon from plutonium may take place easily, since the former is a gaseous element, while the latter is a refractory element. The separation of xenon from iodine may not take place easily, however, since the former is a gaseous element, while the latter is a volatile element. The isotopic compositions of the trapped xenon released from ordinary chondrites and achondrites resemble that ofTakaoka's primitive xenon, which has been mass-fractionated in such a manner that the heavier isotopes are systematically enriched relative to the lighter isotopes.

Photochemical separation of xenon and krypton

A technique is described for the separation of xenon from krypton using photolytically produced fluorine atoms as the reactive species. Stable XeF/sub 2/ is produced when a mixture of xenon, krypton, and fluorine gases is irradiated with near-ultraviolet light. KrF/sub 2/ is not stable at the near room temperature conditions of the experiment. Separation factors (enrichments) greater than 1000 for Xe/Kr are reported for yields of less than 98%. Even higher yields (resulting from longer photolyses) are possible, but then separation factors become slightly smaller.