1. Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02668 Warsaw, Poland
2. Institute of Electron Technology, al. Lotnikow 46, PL-02668 Warsaw, Poland
3. MAX-Lab, Lund University, P.O. Box. 118, S-22100 Lund, Sweden
4. HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany