Advance in diagnostics for high-temperature plasmas based on the analytical result for the ion dynamical broadening of hydrogen spectral lines.
It is well known that the ion dynamics is very important for Stark broadening of spectral lines in high-T plasmas. However, it is usually assumed that with the increase of the plasma density N and/or of the principal quantum number n of the upper level of the radiator, the ionic contribution to the impact width (ICIW) tends to zero. In distinction to that paradigm, by finding an analytical result for the ion dynamical broadening of hydrogen spectral lines, we show here that with the increase of N and/or n, the ICIW does not decrease. Moreover, for practically important ranges of T, N, and n, this "residual" ICIW, being virtually independent of n, can be comparable to the standard electron impact width. This result leads to: (i) a substantial revision of the past of diagnostic conclusions for a variety of high-T plasma experiments; (ii) a much better possibility to deduce from experimental, Stark-broadened line profiles not only the plasma density but also the plasma temperature; (iii) a significant enhancement of the accuracy of N and T obtained from experimental line profiles; and (iv) a substantial revision of simulation models for the ion dynamical contribution that were based on a wrong assumption that the latter vanishes under increasing N and/or n. The consequences are especially important for tokamak plasmas, where the diagnostics based on experimental profiles of high Balmer and Paschen lines is frequently used.
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Physics Department, Auburn University, Auburn, Alabama 36849, USA.