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Abstract: We describe the design and operation of a system for xenon liquefaction in which the condenser is separated from the liquid storage vessel. The condenser is cooled by a pulse tube cryocooler, while the vessel is cooled only by the liquid xenon itself. This arrangement facilitates liquid particle detector research by allowing easy access to the upper and lower flanges of the vessel. We find that an external xenon gas pump is useful for increasing the rate at which cooling power is delivered to the vessel, and we present measurements of the power and efficiency of the apparatus. [Copyright &y& Elsevier]

Abstract: We describe purity measurements of the natural and enriched xenon stockpiles used by the EXO-200 double beta decay experiment based on a mass spectrometry technique. The sensitivity of the spectrometer is enhanced by several orders of magnitude by the presence of a liquid nitrogen cold trap, and many impurity species of interest can be detected at the level of one part-per-billion or better. We have used the technique to screen the EXO-200 xenon before, during, and after its use in our detector, and these measurements have proven useful. This is the first application of the cold trap mass spectrometry technique to an operating physics experiment. [Copyright &y& Elsevier]

Abstract: We extend our technique for observing very small concentrations of impurities in xenon gas to the problem of krypton detection. We use a conventional mass spectrometer to identify the krypton content of the xenon, but we improve the sensitivity of the device by more than five orders of magnitude with a liquid nitrogen cold trap. We find that the absolute krypton concentration in the xenon can be inferred from the mass spectrometry measurements, and we identify krypton signals at concentrations as low as 0.5×10−12 mol/mol (Kr/Xe). This technique simplifies the monitoring of krypton backgrounds for WIMP dark matter searches in liquid xenon. [Copyright &y& Elsevier]

Abstract: We report on the development and performance of a high-sensitivity purity-analysis technique for gaseous xenon. The gas is sampled at macroscopic pressure from the system of interest using a UHV leak valve. The xenon present in the sample is removed with a liquid-nitrogen cold trap, and the remaining impurities are observed with a standard vacuum mass-spectroscopy device. Using calibrated samples of xenon gas spiked with known levels of impurities, we find that the minimum detectable levels of N2, O2, and methane are 1×10−9, 160×10−12, and 60 ×10−12 g/g, respectively. This represents an improvement of about a factor of 10000 compared to measurements performed without a cold trap. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen, nitrogen and methane purification efficiencies for a common zirconium getter are measured in 1050Torr of xenon gas. Starting with impurity concentrations near 10−6 g/g, the outlet impurity level is found to be less than 120 ×10−12 g/g for O2 and less than 950×10−12 g/g for N2. For methane we find residual contamination of the purified gas at concentrations varying over three orders of magnitude, depending on the purifier temperature and the gas flow rate. A slight reduction in the purifier''s methane efficiency is observed after 13mg of this impurity has been absorbed, which we attribute to partial exhaustion of the purifier''s capacity for this species. We also find that the purifier''s ability to absorb N2 and methane can be extinguished long before any decrease in O2 performance is observed, and slower flow rates should be employed for xenon purification due to the cooling effect that the heavy gas has on the getter. [Copyright &y& Elsevier]