New method of 85Kr reduction in a noble gas based low-background detector

TL;DR

The paper introduces a novel krypton reduction method for low-background detectors, combining krypton dilution with existing separation techniques to further lower 85Kr contamination in noble gas experiments.

Contribution

It proposes a new approach of adding 85Kr-free krypton to enhance reduction of 85Kr in xenon detectors, improving background suppression in dark matter and neutrino experiments.

Findings

Measured activity of 25-year-old krypton matches expected levels.

Tested with ancient krypton from 1944, demonstrating high sensitivity.

The method effectively reduces 85Kr concentration beyond current techniques.

Abstract

Krypton-85 is an anthropogenic beta-decaying isotope which produces low energy backgrounds in dark matter and neutrino experiments, especially those based upon liquid xenon. Several technologies have been developed to reduce the Kr concentration in such experiments. We propose to augment those separation technologies by first adding to the xenon an 85Kr-free sample of krypton in an amount much larger than the natural krypton that is already present. After the purification system reduces the total Kr concentration to the same level, the final 85Kr concentration will have been reduced even further by the dilution factor. A test cell for measurement of the activity of various Kr samples has been assembled, and the activity of 25-year-old Krypton has been measured. The measured activity agrees well with the expected activity accounting for the 85Kr abundance of the earth atmosphere in 1990 and the half-life of the isotope. Additional tests with a Kr sample produced in the year 1944 (before the atomic era) have been done in order to demonstrate the sensitivity of the test cell.