Spatial distribution of lost ripple-trapped suprathermal electrons.

Laboratorio Nacional de Fusion. Asociacion EURATOM/CIEMAT, 28040 Madrid, Spain Introduction The ECRH driven convective flux of ripple-trapped suprathermal electrons in low density stellarator plasmas has been mentioned as being related to various features and phenomena: the suprathermal feature and the burst-like phenomena in the ECE emissions [1], the electron-root feature [2] and the phenomenon of electric pulsation [3]. In a previous investigation on TJ-II plasmas [4], fast transitions in confinement regimes were found to be associated to changes in the electron distribution function and to changes in the direct convective losses at the heating region. There, low order rational surfaces located at the gradient region seemed to be affecting the trapping/de-trapping rates. It was also reported [5] that the plasma potential at the core region increased with the characteristic energy of the electron suprathermal electron tail. Here we present the spatial distribution of electron losses to the vacuum vessel and to the graphite limiter detected through their bremsstrahlung emission in the range of the soft x rays. Electron losses are monitored with the SXR tomography diagnostic, using thick Be filters to reduce the contribution of plasma emission, and a planar Ge detector to obtain the spectra [6], see Fig. 1 and 2.