Speaker
Description
The XENONnT experiment, located underground at the Laboratori Nazionali del Gran Sasso, uses a total of 8.6t of high-purity liquid xenon to directly search for WIMP (weakly interacting massive particle) dark matter using a dual phase time projection chamber. Most of the low-energy electronic recoil background is caused by intrinsic contamination of the xenon by Rn-222 with a half-life of 3.8d, which is continuously emanating from the detector materials.
For the reduction of this background, a high-flow online radon removal system was designed and constructed (M. Murra et al, Eur. Phys. J. C 82 (2022) 1104), which uses cryogenic distillation based on the difference in vapor pressure between radon and xenon. The system can be operated in parallel in two modes: At a flow rate of 200 slpm, liquid xenon is extracted from the detector and passed through the system. The cleaning time constant, which only corresponds to one mean lifetime of Rn-222 (5.5d), results in a reduction in radon concentration by a factor of two. An additional extraction of 25 slpm of gaseous xenon provides another reduction factor of about two. With the combined operation of both modes, an extremely low Rn-222 activity concentration of < 1 µBq/kg is achieved, the lowest of any xenon dark matter experiment.
This contribution shows the basic concept of the XENONnT radon removal system and the performance of the system in the XENONnT experiment.
The project is funded by BMBF under contract 05A20PM1.
| Submitted on behalf of a Collaboration? | Yes |
|---|
