Phase-resolved measurements of ion dynamics with laser-induced fluorescence

Abstract

Laser-induced fluorescence (LIF) has become a standard diagnostic for ion temperature and ion drift measurements in plasmas. LIF is non-invasive and provides a high-spatial and a high-energy resolution. With the recent development of advanced laser systems LIF is more and more used to also detect perturbations of the ion-velocity distribution function (IVDF) and to get detailed information about the ion dynamics. This paper reports on a method to perform phase-resolved measurements of the IVDF in periodically perturbed plasmas. As an example LIF measurements during magnetic reconnection are discussed. The parallel component of the IVDF is measured with and without reconnection. If reconnection is driven, the ion temperature is found to be twice as high as without reconnection. The evolution of the IVDF during a reconnection cycle reveals strong variations of the ion temperature correlated with the reconnection drive.