1. Kiel University, Institute of Experimental and Applied Physics, 24098 Kiel, Germany
2. Ruprecht-Haensel Laboratory, Kiel University, 24118 Kiel, Germany
3. ESRF, Experiments Division, 38000 Grenoble, France
4. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
5. ICGM, Univ. Montpellier, CNRS, ENSCM, 34095 Montpellier Cedex 5, France