1. A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland
2. Physics Laboratory, University of Kent, Canterbury CT2 7NR, U.K.
3. ESRF, BP 220, 38042 Grenoble, France
4. Faculty of Earth Sciences, Interdepartmental Laboratory of Structural Research, University of Silesia, Będzińska 60, 41-200 Sosnowiec, Poland