Measurements of the high frequency loss near the plasma resonance in Josephson tunnel junctions

We here present measurements of the microwave loss near the plasma frequency (at 9 GHz) in two 30 × 30 μm
²
Nb-Nbox-Pb Josephson tunnel junctions with critical current density, J
c
, in the range 10 to 70 A/cm
²
. The temperature and amplitude dependence of the high frequency loss is investigated and compared with the differential resistance of the dc characteristic.