Status report on long-time decay measurements of 137Cs radioisotope

TL;DR

This paper reports on an 18-month long measurement of 137Cs decay rates in a low-background underground laboratory to investigate potential variations or modulations in nuclear decay constants.

Contribution

It presents the experimental setup, data processing methods, and initial results of a long-term decay rate measurement of 137Cs conducted underground.

Findings

Data collected over 18 months provides new insights into decay rate stability.

The measurement setup allows for high-precision detection in low-background conditions.

Initial results are discussed, with ongoing analysis to detect possible decay rate modulations.

Abstract

The constancy of nuclear decay rates can be investigated via long-duration precision measurements. It is still an open question whether any (annual) modulation can be observed. Long-lasting nuclear decay rate measurements have been the subject of considerable research effort. A decay rate measurement with a 137Cs source is currently being conducted 30 meters below the ground at the J\'anossy Underground Research Laboratory (JURLab, Csilleb\'erc, Hungary) utilizing a High-purity Germanium (HPGe) detector. The laboratory is the low-radiation-background part of the Vesztergombi High Energy Laboratory (VLAB) on the KFKI campus, Csilleb\'erc, Hungary. From October 2022 to April 2024, data of 18 months' worth have been collected, providing a new opportunity to look for variations in decay rates. The experimental setup, data processing method, and the first results of this measurement are presented here.