The question whether an annual modulation is observable during nuclear decay rate
measurements has long been the subject of research. One of the possible explanations
for the annual variations would be the effect of solar neutrinos, the flux of which
changes in correlation with the Earth-Sun distance. A decay rate measurement with
a Cs-137 source and a HPGe detector is currently being conducted 30 meters below the
ground at Janossy Underground Research Laboratory (Csilleberc, Hungary). The laboratory
is part of the Vesztergombi High Energy Laboratory (VLAB), one of the TOP 50 research
infrastructures in Hungary. From October 2022 to March 2023, data of six months' worth
has been collected, and hence this is a new opportunity to check whether the annual
variation in decay rate can be observed. The laboratory, the experiment, the data
processing method, and the first results are presented in this study.
