Visualization of plasma turbulence with laser-induced fluorescence (invited)

Turbulence is a key factor limiting the performance of fusion devices. Plas ma edge turbulence determines the boundary values of the plasma density and temperature, which in turn determine the internal gradients and controls g lobal plasma transport. In recent years, significant progress has been made in modeling turbulence behavior in plasmas and its effect on transport. Pr ogress has also been made in diagnostics for turbulence measurement; howeve r, there is still a large gap in our understanding of it. An approach to im prove this situation is to experimentally visualize the turbulence, that is , a high resolution 2-D image of the plasma density. Visualization of turbu lence can improve the connection to theory and help validate theoretical mo dels. One method that has been successfully developed to visualize turbulen ce in gases and fluids is planar laser-induced fluorescence. We have recent ly applied this technique to visualize turbulence and structures in a plasm a. This was accomplished using an Alexandrite laser that is tunable between 700 and 800 nm, and from 350 to 400 nm with second harmonic generation. Th e fluorescence light from an argon ion transition has been imaged onto an i ntensified charged coupled device camera that is gated in synchronization w ith the laser. Images from the plasma show a rotating structure at 30 kHz i n addition to small scale turbulence. (C) 2001 American Institute of Physic s.