1. Department of Physics, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy
2. INFN, Laboratori Nazionali di Frascati, Via Enrico Fermi 54, 00044 Frascati, Italy
3. Department of Physics & INFN, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy
4. ENEA, C.R. Brasimone, Camugnano, 40032 Bologna, Italy
5. Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich GmbH, Cauerstraße 1, 91058 Erlangen, Germany
6. INFN, Section of Milan, via Celoria 16, 20133 Milan, Italy