Formation of a Multi-Charged Plasma in the Directed Gas Flow

Extreme-Ultraviolet Light Source for Lithography Based on an Expanding Jet of Dense Xenon Plasma Supported by Microwaves

“…This is possible due to the long duration of microwave pulses for available gyrotrons (50 µs or longer) in comparison with the ion fly time through the chamber (few µs). The most critical part of the discharge is related to its start-up, at which slow gas flow initially consisting of neutral species becomes ionized and accelerated up to ion-acoustic velocity [21][22][23]. Partial preionization of the flow would essentially decrease the average time that an ion spends in low-charge stages and thus accelerates the transition to the stationary regime within the gyrotron pulse duration.…”

“…Nevertheless, this uncertainty may be overcome, and a stable, stationary, continuous, and smooth solution may be obtained if the fluid equations are solved with some very nontrivial boundary condition as proposed in Refs. [21,22]. Recently, this technique was applied and tested in a related study of an EUV light source based on a microwave discharge in a mirror magnetic trap [24].…”

“…In this paper, inspired by the success of recent experiments, we report a model predicting the conversion efficiency into the EUV band in the expanding gas jet and study the prospects of xenon-based EUV sources in present technological circumstances. An essential new feature of xenon discharge is the much higher plasma density(at least two orders of magnitude) than in tin plasma analyzed earlier [21][22][23][24]. Correspondingly, we consider new EUV emission physics taking into account the effects of radiation reabsorption in an optically thick plasma.…”

Formation of UV-radiating strongly non-equilibrium plasma with multiply charged ions in the expanding high-pressure gas jet

“…(6) in the vicinity of the critical gradient (7) results in the following equations for variations of Mach number and the coordinate along the flow [5]: ) there are subsonic and supersonic regimes, separated by separatrix along which the smooth transition from sub-to supersonic movement is only possible. Detailed analysis of such regimes, including non-linear stages far from the critical point, is done in [5]. In particular, it is possible to determine the initial conditions for the flow such that non-linear evolution of Eqs.…”

“…Thus, the linearized equations may be used to classify all possible solutions of the non-linear problem. In limiting cases of strongly subsonic or supersonic flow solutions may be found analytically [4,5]. The subsonic regime is characterized by fast ionization at constant pressure, const, 0 0   n T n T e e and spatial locality limited by variation of the flux cross-section…”