Abstract

Study of atomic and radiative processes in non-stationary non-equilibrium space and laboratory plasmas is the fast-developing domain of physics. Plasmas of high-Z materials are of great interest for generation of radiation in extreme-ultraviolet (EUV) and soft X-ray wavebands for research and applications in extreme-ultraviolet lithography, microscopy of nano-objects (particularly for observation in-vivo) and others. To achieve a suitable ionization degree to emit photons with the energy required, the high-Z plasma should be heated up to tens of electron-volts. Laser pulses and electric discharge current may be used individually or in concert to heat up and to confine the plasma at a suitable temperature. Such discharge- and laser-produced plasmas used in soft X-ray and EUV sources are in non-equilibrium (non-LTE) state as a rule. This leads to a mismatch between the actual conditions of the plasma and its theoretical/computational estimations because of different effects like self-absorption, non-stationary, non-thermal electron distribution etc. leading to changes in ionization states, state populations, emission intensity and spectrum.

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