[en] This work deals with two aspects of the use of pulsed high voltages. The first one relies on the realisation of high energy generators (W>MJ) for magnetic striction plasma experiments (Z-pinch) in order to realize intense X sources (some few keV). The system retained is an inductive storage generator which includes a fast Marx generator (T/4<1 s) and a plasma opening switch (POS). The realization of a Marx generator with a minimized current rise time has led to study a low inductance switch (some few nH): the surface spark gap. The model built works in the ambient air at the nominal voltage of 40 kV and with a current of about 900 kA, and its inductance is lower than 5 nH. Its service life exceeds 1000 firings. The choice of materials, the triggering system, and most of the other influencing parameters of the surface spark gap have been studied. Some applications (system with two surface spark gaps, flat line Marx) of this spark gap are also indicated. The second aspect concerns the generation of microwaves using the electron beam - electromagnetic wave interaction (free electrons laser, Cherenkov plasma tube,..) using a generator developed in the laboratory: the Labutron, which particularity is its high impedance cables (about 1000) that can deliver a micro-second pulse with a stable voltage plateau during 700-800 ns. The work presented concerns the development of a cold cathode diode for the production of the electron beam. The diode built can work at about 400 kV and under an impedance of about 950. Several options are proposed to improve the performances obtained. (J.S.)