Time-resolved EUV spectroscopy in the early stage of laser ablation of carbon

In the early stages of laser ablation the combination of high density and optical opacity makes it difficult to use visible spectroscopy for plasma diagnosis. However, these problems can be overcome by working at shorter wavelengths in the EUV We have used time-resolved EUV emission spectroscopy to study the early stages (1-30 ns) of plasma development in the laser ablation of carbon at an irradiance of 5 GW cm(-2). The ablation was done using a 6 ns Nd:YAG laser at 1.06 mum. The spectra were recorded using a grazing incidence spectrometer with a 5 ns-gated micro-channel plate (MCP) detector. An ion probe operating in the time-of-flight mode was used to measure the ion velocity distribution of the plasma outflow. In the 10-35 run region the predominant line emission was due to Li-like carbon. The temporal variation of the electron density and temperature was deduced by fitting the observed spectrum to a synthetic spectrum calculated using the FLY numerical model of the plasma ionisation and excitation. The temperature deduced from spectroscopy was in good agreement with the estimation from the measured ion velocity distribution in the plasma outflow. (C) 2002 Elsevier Science B.V All rights reserved.