A. Goldgirsh

H. Tawara

V. Fisher

Y. Maron

Yu. V. Ralchenko

National Institute for Fusion Science (NIFS-Repository)

§17. The Composition History of Non-equilibrium Plasma: Rate Equations vs. Time-Dependent Equilibria Fisher, V., Maron, Y., Ralchenko, Yu. V., Goldgirsh, A. (Dept. of Particle Physics, Weizmann Institute of Science, Rehovot 76100, Israel) Tawara, H. One of the most reliable methods for the determination of nonequilibrium-plasma parameters is based on com-parison of time-dependent spectral line intensities with predictions of detailed kinetic models. Here we report on re-sults obtained with our newly devel-oped time-dependent collisional-radiative code designed for studying the behavior of nonequilibrium both Maxwellian and non-Maxwellian plas-mas. Calculations are performed for a neon plasma with account of all charge states (total of 101 terms, mainly for high-charge-state ions). The kinetic processes under consideration are ionization, excitation and deexcitation by electron impact, spontaneous radiative transition, photo-recombination, and three-body recom-bination. In order to enable calculations with arbitrary electron distribution functions we use energy-dependent cross-sections to obtain the rates of collisional processes. Most of relevant data ·on electron-ion collisions were taken from the NIFS Atomic Database or calculated with the "ATOM" code by L.A.Vainshtein. In many cases where plasmas with time-varying electron density and tem-perature are modelled it is assumed that at each instant the plasma is in equilib-rium that can be collisional-radiative (CRE), coronal (CE) or local thermo-dynamical (L TE). Here, we present re-sults for fully time-dependent calcula-tions, as given for example, in Figure 1, 254 where the population ratio (ls2p 3P)/(ls2p 1P) for He-like Ne IX is pre-sented. This ratio is calculated for ion density Ni=1019 cm-3 and triangular profile of temperature: linear increase from 5 e V at t = 0 to 1 ke V at 10 ns, and then linear decrease to 5 e V at 20 ns. a:-106 r-~.:::---._----r----;:~c:::::::==.---,-------r~ ~a. 105 N (/) ~ 104 0 ~ 103 a:-"'a. 102 N Ill ~101 0 -Code ------ CE LTE ·----CRE  ; ... - ~ - --- ----- ~-· ~ 10°~~--~~~--~~--~~ O.Os 5.0ns 10.0ns 15.0ns 20.0ns Time Fig. 1. The ratio presented in Figure 2 is calculated for a linear rise in Ni from 5· 1019 at t = 0 to 2·1020 cm-3 at 0.5 ns followed by a linear decrease to 5·1019 cm-3 at t = 1 ns. A similar triangular profile of the temperature with 100 eV at t = 0 and Te = 500 eV at maximum (0.5 ns) has been taken. This model can be relevant to formation of hot and dense plasmas. -Code -------- LTE · ·CRE Time Fig. 2. One can see that the ratio of populations obtained with rate equations and with various equilibrium models may differ by a few orders of magnitude. Plasma parameters derived from these ratios will also differ significantly. 

The Composition History of Nonequilibrium Plasma: Rate Equations vs. Time-Dependent Equilibria

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