Lézeraktív, hullámvezető és elektrongyorsító plazmaközeg vizsgálata saját fejlesztésű kapilláris Z-pinch specifikus MHD modell alkalmazásával

Abstract

Starting from the three fundamental transport processes in a plasma (particle, momentum and heat transport) I have developed an ”one-fluid” two-temperature 0D and 1D MHD model, which was based on assumptions made for typical capillary Z-pinch in accordance with literature and our experimental experiences. Regarding the 0D or simplified MHD model, further simplification was conducted by using a Lagrangian specification of the flow field and omitting insignificant components. As a result, I have obtained equations of the model (Eqs. 6.1a – 6.1d). This model allows easy and rapid analysis of time evolution of the plasma parameters, so that it can be useful for solving problems related to development of soft X-ray lasers and Z-pinch photolithography XUV sources. In order to know the spatial distribution of the plasma parameters I have increased degree of freedom of the model by involving radial dependence. Here, I have switched to the Eulerian specification of the flow field since it provides real distributions. The obtained equations can be also gathered into one system of equations (Eqs. 6.2a – 6.2f) completing with constraint of number density of the ions and the current density (Eq. 6.2g). By comparing computed and measured results I have carried out the dynamic validation of both models. In a related series of measurements my colleague and I have measured pinching time of Z-pinch discharge of different initial setups. As it turned out, in 90% of the cases the relative deviation was under 20%. Regarding the 1D MHD model, I have carried out the spatial validation too by comparing the time averaged transmittance distribution of the plasma column computed for 46.9 nm spectrum line of the neon like Ar+8-ions with observed transversal distribution of the X-ray laser radiation. The related experimental results (phosphor screen captures) I have used from an experiment previously done by our research group [50]. It has been proved that distributions are consistent with the experimental observations, but the computed pulse duration is about 3...4 times greater than the measured one and there is about 0.16...0.2 mbar systematic shift between theoretical and real initial pressures.