Non-equilibrium experiments in LTS Josephson double tunnel devices

Superconducting Tunnel Junctions (STJ) are promising devices as a next generation of nuclear and optical detectors Non-equilibrium experiments can pro,ide useful information on the behaviour of a perturbed superconductor. Among possible non-equilibrium sources, we used quasi-particle injection in three-terminal double tunnel junction de,ices and a laser pumping source. We investigated the effect of perturbed renditions on sub-harmonic gap structures, which are present in I-V characteristics of high quality Nb-based STJs. Experimental results concerning the change of the energy gap measured at V=2 Delta/2e show features which can not be completely explained in terms of simple heating effects.