MEASUREMENT OF THE ND-150 HALF-LIFE T-1 2(2-BETA-2-NU) WITH A TIME PROJECTION CHAMBER IN A MAGNETIC-FIELD/

The positive effect is obtained in an experiment devoted to searches f or the two-neutrino double beta decay of Nd-150 With a time projection chamber. The half-life T-1/2(2 beta 2 nu) = (1.88(-0.39)(+0.66stat) /- 0.19(syst)) X 10(19) yr is determined from an analysis of events ac cumulated for two samples - one enriched in Nd-150 to 92% and the othe r of natural isotopic content. The effect-to-background ratio is 4/1. The estimate of the background from intrinsic radioactive impurities i n the samples is obtained experimentally with the aid of special calib ration sources with a known concentration of U-238 and Th-232. The use of these calibration sources for generating two-electron events makes it possible to experimentally verify the calculated efficiency of the setup with respect to 2 beta 2 nu decay and to estimate the systemati c error of the result.