Effect of compression of a laser plasma on the generation of harmonics and hard x radiation

A compression of a plasma produced at a conical target by a low-intensity beam ($q\lesssim$10 GW/cm$^2$) from a CO$_2$ laser has been studied. The effect of this compression on the onset of the parametric instability responsible for the generation of harmonics and of hard x radiation has also been studied. A qualitative interpretation of the results is offered.