Energy loss of α-particle in the non-equilibrium plasma of deuterium mixed with lithium

Abstract

The stopping power of compressed and highly ionized deuterium (D) plasma mixed with lithium (Li), in which the electron and ion temperatures are non-equilibrium (i.e., Te≠Ti), to the injected α-particles is studied. Wide ranges of temperature (0.5 keV∼10 keV) and density (1 g/cm3∼500 g/cm3) of D-Li mixing plasmas are considered. The numerical results show that, in the temperature equilibrium state, the change ratio of stopping power (denoted by η) increases positively with the increase of the fraction of Li (denoted by xLi). However, in some non-equilibrium dense plasma states, η may increase negatively with the increase of xLi. The corresponding nonlinear response of η to xLi may become more (less) remarkable if Ti>Te ( Ti <Te), which suggests that the collective excitation in the stopping power of D-Li mixing plasmas in which Ti>Te ( Ti <Te) will be enhanced (suppressed) due to the non-equilibrium temperature effect. As a result, the change ratio of deposition depth of α-particles (denoted by χ) for the non-equilibrium case of Te>Ti rather than Ti>Te seems to be closer to that of equilibrium cases. Furthermore, our results show that more than 60% of energy of injected α-particles is deposited into the electron species, and the energy deposited into the electron component (Ee/E0) is a monotonic decay function of xLi. In addition, relative to the equilibrium results, we find that Ee/E0 will slightly increase (decrease) when Ti>Te (Te>Ti). The findings and analysis in this work indicate that the non-equilibrium implosion with Te>Ti may be more controllable than that with Ti>Te, which may be useful for the advanced development of fusion propulsion systems, in which DLi is a potential fuel option.