1. National Centre for Nuclear Research, A. Sołtana 7, Otwock-Świerk 05-400, Poland
2. Institute of Electronic Materials Technology, Wólczyńska 133, Warszawa 01-919, Poland
3. Warsaw University, Institute of Experimental Physics, Hoża 69, Warszawa 00-681, Poland
4. HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg, Germany