Study of nonlinear mode couplings in a magnetized plasma column : Benefits of fast camera imaging

The broadband spectrum of fluctuations observed in fusion plasmas can result from nonlinear high order wave-wave interactions, which can transfer the energy contained in a few modes to a multitude of modes. A nonlinear energy transfer involves at least three modes and requires a frequency and phase match between the modes. A well-known tool to measure this match is the bicoherence, which corresponds to a third order spectrum of fluctuations. This contribution presents investigations conducted on the linear device Mirabelle. Complementary to Langmuir probe measurements, camera measurements have been used to compute wavelet bichorence. Following a short introduction of the experimental setup, first results of mode number bicoherence computation are presented. Finally the new perspectives but also the new challenges associated with the camera as a turbulence diagnostic are discussed.