Space-resolved spectral diagnosis of line-shaped laser-produced plasmas

摘要

Summary form only given, as follows. The experiments were carried out at the LF12 Laser Facility of SIOFM. A 1.05 /spl mu/m laser beam with 200-600J energy and about 900 ps duration was focused onto magnesium slab targets by means of a novel cylindrical lens array combined with an asperical lens. A spectral diagnostic technique was used to study the properties of fine-shaped laser-produced plasmas. With the help of a new pinhole flat-crystal spectrograph, the spatial distributions of electron temperature and density along the normal of target surface in line-shaped plasmas were obtained. The Stark-broadened Ly-/spl alpha/ line wings of hydrogenic ions were used to deduce the electron density beyond the critical surface. A fitting program has been developed. The results were compared with a theoretical model of distributed absorption of laser light by plasma. The data of the electron density and width of conduction region are in good agreement with the theoretical predictions of a planar laser-driven ablation model of nonlocalized absorption. The results also show that the plasma fluid dynamic behavior of line- and spot-shaped laser-produced plasmas are quite different due to their different expansion dimensions.