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UP: Fachverband Umweltphysik

UP 9: Poster session

UP 9.2: Poster

Mittwoch, 7. März 2018, 16:15–18:15, Orangerie

Argon purification system for ³⁹Ar measurements with Argon Trap Trace Analysis (ArTTA) — •Viola Rädle¹, Philip Hopkins¹, Arne Kersting¹, Maximilian Schmidt^1,2, Lisa Ringena², Zhongyi Feng², Emeline Mathouchanh¹, Sven Ebser², Markus K. Oberthaler², Werner Aeschbach¹, and Stefan Beyersdorfer¹ — ¹Institut für Umweltphysik, Heidelberg, Deutschland — ²Kirchhoff-Institut für Physik, Heidelberg, Deutschland

Noble gas radioisotopes are ideal environmental tracers because of their chemical inertness. In particular, ³⁹Ar is of great importance as it is the only tracer covering the age range of 50 to 1000 years. However, measuring the ³⁹Ar/⁴⁰Ar ratio is challenging due to an extremely low isotopic abundance in the order of 10⁻¹⁶ and a long half-life of 269 years. In order to apply the emerging technique ArTTA, approx. 1 mL of pure argon are required, corresponding to about 5 L of water or 2-5 kg of ice. Large amounts of water (e.g. groundwater) can already be degassed in the field using a portable device based on a membrane contactor. Smaller samples are transported to the laboratory and are processed by a newly developed argon purification setup. Here, the gas dissolved in water or enclosed in ice is extracted. In a second step, it is purified by removing the reactive gases on titanium sponge getters at 900 ^∘C and 20 ^∘C, leaving only noble gases, hence resulting in an argon purity of > 99 %. Finally, the argon is frozen on an activated charcoal trap and can be measured using ArTTA. The new setup can purify one ice sample or up to three water samples per day with a yield > 95 %.