Аннотация:In this chapter we introduce our recent studies on terahertz (THz) andX-ray emission generated in an Ar gas-cluster jet under irradiation with high-intenseultrashort laser pulses. We carried out a numerical simulation of cluster formation processes in a supersonic jet produced under adiabatic extension of gaseous Arinto vacuum, which shows that the concentration ratios among non-clusterized Armonomers, small-size Ar clusters and large-size Ar clusters significantly vary alongthe jet. The chapter presents experimental results on THz and X-ray emission generatedby irradiation of the jet with intense femtosecond laser pulses at variousdownstream distances measured from the nozzle outlet along the axis of symmetryof the nozzle. It is shown that THz and X-ray emission from the jet is a useful toolfor the study of clustering dynamics in the course of free expansion of gas througha nozzle into vacuum.