Search for two-neutrino 2K capture in ¹²⁴Xe: the method and preliminary results

The technique used in the experiment in the search for the process of 2K2ν-capture in ¹²⁴Xe using large high-pressure proportional counters is briefly described. The measurements with a xenon sample enriched to 21% (or ~57 g) of the ¹²⁴Xe isotope carried out for 3340 hours yielded a zero signal. The resultant upper limit on the ¹²⁴Xe half-life with respect to the 2ν-mode of the nuclear capture of two K-shell electrons amounts to T_1/2>4.6 10²¹ yr at the 90% confidence level.