The first experimental campaign using the High Power Laser System at ELI-NP took place in E4 experimental area, from 18 March until 27 March 2020, when it was interrupted for COVID19 related safety measures. The experiment, the result of the collaboration with IZEST institute in France, intended to be a test for the operation of the laser system and also a first step towards the upgrade of HPLS. It addressed the spectral broadening of ultrashort pulses in thin plates of
non-linear material (BK7 and OKP), needed as a prerequisite for the post-compression of the 23 fs pulses of HPLS and for peak power enhancement beyond the nominal value of 10PW per arm.
The laser demonstrated outstanding quality during the campaign. Performance of the laser is described, and some preliminary results are presented.