Low Perturbative Observation of Moderately Coupled Plasma Using Probe Laser Induced Fluorescence

Abstract

A low-perturbative probe laser induced fluorescence (LIF) system has been developed to observe extremely low temperature one-component plasma. The ion temperature was controlled using a laser cooling method at the temperature domain much lower than room temperature. Since the undistorted spectra can be obtained using this probe-LIF measurement system, a quantitative evaluation of the spectrum shape of the laser-cooled plasma was achieved. The ion temperature is obtained from the Doppler width, and the Coulomb coupling parameter Γ is calculated as 0.02 to 8. The results show the ability of the experimental setup for controlling and observing the plasma over the connecting region between weakly coupled state and strongly coupled state. On the other side, an unexpectedly wide Lamb dip generated by the cooling laser was found. It is very interesting to clarify the broadening mechanism of the dip, since it contains the information of the elementary processes in the moderately coupled plasma