Calculation of tin emission spectra in discharge plasma: The influence of reabsorption in spectral lines

On the maximum conversion efficiency into the 13.5-nm extreme ultraviolet emission under a steady-state laser ablation of tin microspheres

“…As the temperature drops in time (remaining in all the three cases practically uniform over the considered volume), the ratio of the in-band to the total radiative cooling power produces the SP(t) curve; by mapping the SP(t) curve to the T(t) curve from the same simulation, we obtain the SP(T) dependence. Importantly, thus obtained SP(T) function does not depend on the decay rate of T because all the simulations have been done by using the spectral opacity tables, prepared under the quasi-stationary assumption 15 for the level kinetics, i.e., by assuming that the populations of all the ionization stages and excited levels instantaneously relax to the steady-state solution of the corresponding rate equations for given q and T. It is important to emphasize that the curves in Fig. 1 have been obtained under exactly the same approximations in the CR plasma model as all the other calculations of CE for the laser ablated Sn droplets discussed in this work.…”

“…Calculation of the adequate spectral absorption coefficient k for the transfer equation 1is a separate complex problem. Here, we use the approach 15 based on quasi-stationary opacity tables that are prepared beforehand by finding a steady-state solution (for any given q; T pair) to a large system of CR rate equations for populations of the relevant atomic levels. The key uncertainty in this procedure is the a priori unknown intensity I of the local radiation field, which strongly affects the EUV emissivity of the Sn plasma.…”

“…The key uncertainty in this procedure is the a priori unknown intensity I of the local radiation field, which strongly affects the EUV emissivity of the Sn plasma. 15 In this work, we used partially opaque k tables, calculated with the THERMOS package 13 under the assumption of a black-body radiation field within the 10% bandwidth around k ¼ 13:5 nm, and zero radiation field outside this range. Such an approximation appears reasonable for the purposes of the present study, where the sought-for optimum plasma configurations have the optical thickness of the order of unity in the narrow bandwidth around 13.5 nm where k peaks (see Fig.…”

The ion broadening calculating method for a nonequilibrium plasma

“…Положение и сила линий могут быть скорректированы с использо-ванием более точных программ или эксперимента, а также свернуты на некото-рой сетке по энергии фотонов, позволяющей передать основные особенности описываемого спектра (методика RUSAM [2,7]). Набор конфигураций в базе данных формируется в соответствии с условиями поставленной задачи.…”

“…При моделировании неравновесной малоплотной плазмы только часть линий перекрывается и плазма близка к прозрачной, поэтому при расчетах профилей линий в лоренцевской ширине учитывались только естественное и электронное уширение, что не приводило к большим ошибкам при вычислениях [2].…”