Ion Temperature and Coulomb Coupling Parameter of Ultracold Neutral Plasma in Ion Equilibration Stage

doi:10.19596/j.cnki.1001-246x.8554

Abstract

Abstract:

Using a newly developed velocity map imaging apparatus coupled with a magneto-optical trap, we measured ion temperature and Coulomb coupling parameter of ultracold neutral plasma (UNP). We carried out numerical simulation in early evolution of UNP. The experimental and simulation results showed that the disorder-induced heating mechanism led to a rapid rise in ion temperature during the ion equilibration, and the Coulomb coupling parameter dropped to 2.5. Furthermore, we found that the plasma expansion velocity would quickly approach the thermal velocity of ions in the ion equilibration, which results in a higher Coulomb coupling parameter than experimental values.

Key words: ultracold neutral plasma, disorder-induced heating, Coulomb coupling parameter

Feng FANG, Wenchang ZHOU, Changjie LUO, Yufan LI, Jie YANG. Ion Temperature and Coulomb Coupling Parameter of Ultracold Neutral Plasma in Ion Equilibration Stage[J]. Chinese Journal of Computational Physics, 2023, 40(3): 275-281.

Figures/Tables 5

Fig.1 A schematic of experimental setup

Fig.2 (a) A detected imaging result at delay time td= 0 ns; (b) A slice cut of three-dimensional velocity distribution of ions obtained through Abel inversion; (c) Velocity distribution obtained from three-dimensional distribution shown in panel of (b)

Fig.3 Measured velocity distributions (solid dots) and corresponding fitting results (solid lines) at different delay time

Fig.4 (a) Evolution of ion temperature (The black solid line, the blue dashed line and the red solid dots represent the results of CPT simulation, calculation by Eq. (2) and experimental measurement, respectively.) (b) Evolution of Coulomb coupling parameter Γ (The black solid line and the red solid dots are the results of CPT simulation and experimental measurement, respectively.)

Fig.5 Evolution of rms velocity of ions from CPT simulation and expansion velocity calculated with self-similar expansion model

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