To investigate the internal structure of LSD waves, electron density distribution ne was measured by two-wavelength Mach-Zehnder interferometer and electron temperature Te was by emission spectroscopy. As a result, peak values of ne and Te were about 2 × 1024m-3 and 30,000K, respectively. Based on the measured properties, laser absorption coefficient was calculated. It showed that incident laser energy was perfectly absorbed in a layer much thinner than a plasma layer, situation of which was not predicted by the conventional LSD model. Measured ne at the shock front was not zero while LSD was supported. This suggested that the precursor electrons exist ahead of the shock wave.
