[en] One of the most efficient sources that release pulsed X-radiation in the keV range appears to be the interaction of cluster jets of rare gas (Ar, Kr an Xe) with a sub-picosecond laser impulse. The measurement of the length of the X-ray impulse is challenging, one of the possible measurement method is an inter-correlation method based on the laser assisted Auger decay. In that method a metal target is irradiated with the pulsed X photon flux and the length of the X impulse is deduced from the Auger photoelectron spectra produced simultaneously from the X impulses and from the laser radiation. This method requires a high Auger photoelectron signal emitted from the target while the probability of the Auger effect is usually low. This article deals with an optimization of such a signal and it is shown that the best experimental conditions are: 30 bar of Xenon irradiated by 250 fs laser radiation impulses set on 800 nm, in that case we get a lighting power of 2.10¹⁶ W/cm² and a pure copper target submitted to the X-ray flux releases Auger photoelectrons whose energy spectrum presents a peak at 62 eV. (A.C.)