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

Abstract

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.

Efficient Separation of Ar and Kr from Environmental Samples for Trace Radioactive Noble Gas Detection

“…There have been several reports on the systems of Kr separation from "air-like" gases [5, 10, 25, 31−33]. A method based on frozen charcoal trap and gas chromatography [5,32] has been applied for several liters of gas samples extracted from groundwater. A special krypton purification system for more than 100 L of bulk gas was reported by using several gas chromatographic steps, which has been applied in 81 Kr dating with AMS [10].…”

Analysis of Krypton-85 and Krypton-81 in a Few Liters of Air

“…13,22−27 The sample size varies from several hundred liters down to 5 L with a Kr recovering efficiency of about 80%. 28,29 However, there is a need to recover krypton efficiently from smaller samples. The present ATTA instruments handle typically 5−10 μL of krypton gas which can be recovered from air samples of 5− 10 L. By improving the detection efficiency and eliminating the cross-sample contamination effect in the ATTA measurements, 20,21,30 the sample size can be potentially reduced to 1 L of air or even less.…”

“…It should also be airtight avoiding contamination from ambient air. There have been reports on the separation systems for recovering krypton from gas samples using cryogenic distillation, titanium gettering, gas chromatographic separation, or a combination of these methods. ,− The sample size varies from several hundred liters down to 5 L with a Kr recovering efficiency of about 80%. , However, there is a need to recover krypton efficiently from smaller samples. The present ATTA instruments handle typically 5–10 μL of krypton gas which can be recovered from air samples of 5–10 L. By improving the detection efficiency and eliminating the cross-sample contamination effect in the ATTA measurements, ,, the sample size can be potentially reduced to 1 L of air or even less.…”