A fast, high‐densityz‐pinch discharge is suitable for the study of CO2laser‐plasma interactions. The plasma was investigated temporally and spatially using a variety of optical diagnostic techniques including streak and shadowgram photography, spectroscopy, and Thomson scattering off ion acoustic fluctuations. Peak electron densities of 4×1019cm−3and ion temperatures of 50 eV are observed. Shadowgrams show that at peak compression the plasma consists of an inner dense corene≳1019cm−31 mm in diameter surrounded by a low‐density regionne∼1018cm−3that extends to a diameter of 4 mm.