[1] Univ Naples Federico II, Dept Phys E Pancini, I-80126 Naples, Italy
[2] Consiglio Nazl Ric ISASI, I-80078 Pozzuoli, Italy
[3] Univ Naples Federico II, Scuola Super Meridionale SSM, I-80138 Naples, Italy
[4] Fluid O tech SRL, I-20094 Corsico, Italy
[5] CNR SPIN, Inst Supercond Oxides & Other Innovat Mat & Device, I-80126 Naples, Italy