[1] Helmholtz Zentrum Dresden Rossendorf, Inst Ion Beam Phys & Mat Res, D-01328 Dresden, Germany
[2] Julius Maximilian Univ Wurzburg, Expt Phys 6, D-97074 Wurzburg, Germany
[3] Julius Maximilian Univ Wurzburg, Wurzburg Dresden Cluster Excellence Ct Qmat, D-97074 Wurzburg, Germany
[4] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[5] Tohoku Univ, Grad Sch Engn, Dept Quantum Sci & Energy Engn, 6-6-01-2 Aza Aoba Aramaki,Aoba Ku, Sendai 9808579, Japan
[6] Natl Inst Quantum & Radiol Sci & Technol, Takasaki, Gunma 3701292, Japan
[7] Tohoku Univ, Dept Mat Sci, 6-6-02 Aramaki Aza,Aoba Ku, Sendai 9808579, Japan
[8] Tech Univ Dresden, D-01062 Dresden, Germany