Prior to the installation in the final destination in the Gran Sasso laboratory, the VIP apparatus
was set up and tested at the LNF-INFN laboratory. First measurements were performed with current circulating in the copper target (about 10 days with 40A current) and a background measurement without current with the same measurement time. The obtained energy-calibrated x-ray spectra are shown in figure
2. The spectra show the copper x-ray lines sitting on the continuous background but no other x-ray lines proving the high purity of the structure materials used in the VIP setup.