Removing krypton from xenon by cryogenic distillation to the ppq level

Understand

The XENON1T experiment aims for the direct detection of dark matter in a cryostat filled with 3.3 tons of liquid xenon.

• In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low.
• One major contributor is the $\beta$-emitter $^{85}$Kr which is an intrinsic contamination of the xenon.
• For the XENON1T experiment a concentration of natural krypton in xenon $\rm{^{nat}}$Kr/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10$^{-15}$ mol/mol) is required.