Applied Radiation and Isotopes
Volume 67, Issue 5, May 2009, Pages 918-921
Mikael Hult a, J.S. Elisabeth Wieslander a, c, Gerd Marissens a, Joël Gasparro a, Uwe Wätjen a and Marcin Misiaszek b
a) European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel, Belgium
b) M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymona 4, 30-059 Krakow, Poland
c) Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä, Finland
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Abstract
The radioactivity of 180mTa has never been detected. The present attempt to detect it was carried out using a newly developed HPGe sandwich spectrometer installed 500 m water equivalent underground in the HADES laboratory. The sample consisted of 6 discs of tantalum of natural isotopic composition with a total mass of 1500 g and a total mass for 180Ta of 180 mg. The sample was measured for 68 days and the resulting lower bound for the half-life of 180mTa was 2.0×1016 y, which is a factor of 2.8 higher than the previous highest value