Slow pulsed capillary discharges are under investigation for use as plasma channel waveguides in laser-wakefield acceleration. In this study, we present a non-local thermal equilibrium (non-LTE) plasma model with a model for the wall temperature coupled to it. This model is used to describe an example of a slow pulsed capillary discharge, and the results are compared with experimental results. The agreement is satisfactory, indicating suitability of our model. Significant deviations from LTE are found during the formation of the plasma channel. The model is also used to study the influence of the discharge current on the guiding properties. It was found that this influence is small over most of the current range that was investigated.

Xenon and tin both are working elements applied in discharge plasmas that are being developed for application in extreme ultraviolet (EUV) lithography. Their spectra in the 10-21-nm-wavelength range have been analyzed. A fully analytical collisional-radiative model, including departure from equilibrium due to a net ionization rate, was used to simulate the EUV spectra. Detailed Hartree-Fock calculations, using the COWAN package, were applied for determination of the energy levels and optical transition probabilities of the 8+ to 12+ ions of both elements. For the calculation of the radiation, the opacity of the plasma was taken into account. Time-resolved measurements of the spectra from ionizing phases of two different discharge plasmas were corrected for the wavelength-dependent sensitivity of the spectrometer, and compared to the results of the simulations. Fairly good agreement between the experiments and the model calculations has been found.

Plasmas, produced by a neodymium yttrium aluminum garnet ͑Nd:YAG͒ laser pulse focused on a small water droplet and used for the generation of extreme ultraviolet light, can be described by a relatively simple model due to the fact that thermodynamic equilibrium can be assumed for the most important phase. Only three time-dependent variables-radius, expansion speed, and internal energy-are needed to describe the physics of the plasma. Nevertheless, it predicts quantities such as the size and the spectrum rather well. It is expected that the theory and the model presented here can also be applied to other laser-produced plasmas.

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