Commissioning of a 1-m distillation plant to remove krypton out of xenon

The XENON1T experiment aims for the direct detection of dark matter in the form of Weakly Interacting Massive Particles (WIMPS) and is now under construction. For this purpose a dual-phase TPC, filled with xenon is used, aiming for a fiducial volume of 1 ton to increase the sensitivity to WIMP-nucleon cross section by 1.5 orders of magnitude compared to current experiments. One dominant radioactive contamination, which one needs to reduce to reach the sensitivity, is ⁸⁵Kr, which has a beta-decay with an endpoint energy of 687keV. Therefore, the xenon has to be purified to a concentration of <0.1ppt (parts per trillion) natural krypton in xenon. This talk reports about the commissioning of a cryogenic distillation plant to remove krypton out of xenon, using 1m of package material, as a milestone on the way to a distillation column using 3m package material. Different diagnostics tools, like a ^83mKr tracer method and cold trap-enhanced mass spectrometry, allow to characterize the efficiency of the system.