Intrinsic radioactivity of a crystal and decays of Eu

✍ Scribed by P. Belli; R. Cerulli; F.A. Danevich; B.V. Grinyov; A. Incicchitti; V.V. Kobychev; M. Laubenstein; S.S. Nagorny; A.V. Tolmachev; V.I. Tretyak; R.P. Yavetskiy

• Book ID: 103856279
• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 173 KB
• Volume: 572
• Category: Article
• ISSN: 0168-9002
• DOI: 10.1016/j.nima.2006.12.025

✦ Synopsis

A small Li 6 EuðBO 3 Þ 3 crystal (2.72 g) was measured deep underground at the Gran Sasso National Laboratories with a HP Ge detector of 408 cm 3 during 1500 h. While the crystal is not polluted by usual radioactive contaminants (only limits on the activity of U/Th chains, 40 K, 60 Co, 137 Cs were set on the level of 0.01-1 Bq/kg), the presence of radioactive 152 Eu and 154 Eu is evident; these are created in capture of neutrons by naturally abundant 151 Eu and 153 Eu. The measured activities correspond to 0.95 and 0.21 Bq/kg for 152 Eu and 154 Eu, respectively, with a ratio far from the standard expectation. As by-products, limits on half lives for the a decays 151 Eu ! 147 Pm ðE exc ¼ 91:1 keVÞ and 153 Eu ! 149 Pm are determined as T 1=2 42:4 Â 10 16 yr and T 1=2 41:1 Â 10 16 yr, respectively.