k spectra of Thomson scattering temperature profiles at the TJ-II stellarator

High resolution Thomson scattering temperature profiles at the TJ-II stella rator are subjected to spectral analysis. The obtained k spectrum is very r obust in shape. While its amplitude has been shown previously to scale inve rsely with the collisionality, here it is found that its shape is independe nt of plasma configuration (magnetic well, iota), global plasma parameters (temperature, density) and radial position (centre, edge). The shape is als o found to be very similar to that of k spectra obtained with Langmuir prob es in the edge of TJ-II and of k spectra obtained using other techniques in other devices. The spectral shape is characterized by a 'knee' at k = 500- 1000 m(-1) and a steep decay at large K. Self-similarity analysis reveals t he existence of a high degree of self-organization dominated by structures of around 2.5 cm in size.