1. Department of Physics and Energy, University of Limerick, Plassey Road, Limerick, Ireland
2. School of Physics, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland
3. Department of Materials Sciences and Metallurgy, University of Cambridge, 27 Charles Babbage Road, CBS 0FS Cambridge, United Kingdom
4. Institute of Power Engineering (IEn), ul. Mory 8, 01-033 Warsaw, Poland