Comparative analysis of spectra of the background of the proportional counter filled with Kr, enriched in Kr-78, and with Kr of natural content

TL;DR

This study compares background spectra of a proportional counter filled with enriched and natural krypton, setting new limits on the half-life of $^{78}$Kr for 2K-capture based on experimental data.

Contribution

It provides a comparative analysis of background spectra for different krypton fillings and establishes a new lower limit on the half-life of $^{78}$Kr for 2K-capture.

Findings

Background spectra differ between enriched and natural krypton.

New half-life limit for $^{78}$Kr 2K-capture: T$_{1/2} geq 2.0 imes 10^{21}$ years.

Extended measurement time improves sensitivity.

Abstract

The results of the experiment searching for 2K-capture with large low-background proportional counter are presented. The comparison of spectra of the background of the proportional counter filled with Kr enriched in $^{78}$Kr (8400 hr) and with natural Kr (3039 hr) is given. A new limit on the half-life of $^{78}$Kr with regard to 2K-capture, T$_{1/2}\geq2.0\cdot10^{21}$ yrs (95% C.L.) has been obtained.