Spectroscopic Observations of Structures in an Expanding Laser-Produced Plasma

The emission of laser-produced plasmas in the XUV region has been observed with a novel technique that uses a toroidal mirror as focusing element, achieving a high spatial resolution on the plasma. The profiles of the resonance lines Be IV Lyman α and Be III 1s 2-1s 2p appear symmetrically split in two components far from the target (> mm). This effect, observed also for other resonance lines, can easily be interpreted as a motional Doppler shift. This indicates a minimum of ion density in the centre of the plasma expanding in a near conelike shape around the normal to the target.