Krypton Concentration Monitoring in Cryogenic Distillation for XENON1T employing a Radioactive 83mKr Tracer(pdf)
Intrinsic contamination with the long-lived β-emitter 85Kr constitutes a major source of electronic recoil background in xenon-based dark matter direct detection experiments. For the XENON1T experiment a reduction of the total krypton concentration down to 0.5 ppt is necessary in order to achieve the detector‘s design sensitivity. While this can be achieved with a cryogenic distillation column novel diagnostics are needed in order verify distillation performance in this regime inaccessible to commercially available RGAs. A radioactive tracer method utilizing the isomer 83mKr for online monitoring of the distillation performance will be introduced in this talk. The focus will be on modeling the relationship between the measured 83mKr decays and the krypton concentration in the column. Performance measurements with a single-stage distillation setup in Münster will be presented.