Author: Nakanishi, T.
Paper Title Page
TUPP01 Quantitative Determination of 146Sm/147Sm Ratios by Accelerator Mass Spectrometry with an ECR Ion Source and Linear Acceleration for 146Sm Half-Life Measurement 43
 
  • N. Kinoshita
    UTTAC, Tsukuba, Ibaraki, Japan
  • P. Collon, Y. Kashiv, D. Robertson, C.J. Schmitt, X.D. Tang
    University of Notre Dame, Indiana, USA
  • C. Deibel
    MSU, East Lansing, Michigan, USA
  • C. Deibel, B. DiGiovine, J.P. Greene, D. Henderson, C.L. Jiang, S.T. Marley, R.C. Pardo, E. Rehm, R.H. Scott, R.C. Vondrasek
    ANL, Argonne, USA
  • T. Nakanishi, A. Yokoyama
    Kanazawa University, Kanazawa, Japan
  • M. Paul
    The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
 
  Funding: Supported by U.S. DOE, Office of Nuclear Physics, contract No. DE-AC02-06CH11357, NSF JINA Grant Nr. PHY0822648 and Science Research Prog. of Japan Society for the Promotion of Science (20740161)
The alpha-decaying 146Sm nuclide is used for chronology of the Solar System and silicate mantle differentiation in planets. We performed a new determination of 146Sm half-life by measuring 146Sm/147Sm alpha activity and atom ratios in 147Sm activated via (g,n), (n,2n) and (p,2n) reactions and obtained a value (68 Myr), smaller than that adopted so far (103 Myr), with important geochemical implications*. The experiment required determination of 146Sm/147Sm ratios by high-energy (6 MeV/u) accelerator mass spectrometry to discriminate 146Sm from isobaric 146Nd contaminant. Activated Sm targets were dissolved, chemically purified and reconverted to metallic Sm. Sputter cathodes, made by pressing the Sm metal into high-purity Al holders, were used to feed the Argonne ECR ion source. 146Sm22+, 147Sm22+ ions were alternately injected and accelerated with the ATLAS linac by proper scaling of ion source and accelerator components. A tightly-fitted quartz cylindrical liner was inserted in the ECR plasma chamber to reduce contamination from the walls. 146Sm ions were eventually counted in a gas-filled magnet and 147Sm ions either measured as charge current or counted after proper attenuation.
* N. Kinoshita et al., Science 334, 1614 (2012)