RFP states characterized by the presence of an hot helical structure in the plasma core have shown a significative improvement in the plasma performances. In this work we focused on DAX (Double AXis) states, in which the hot island is surrounded by a separatrix and does not cross the plasma centroid. These states, with respect to SHAx --or Single Helical Axis, [1]- , show smaller thermal structures, but the $\nabla $T$_{e}$ strength suggests a drastic local reduction of energy transport. The analysis relies on data obtained by the Main Thomson Scattering [2] and by the multichord double filter SXR spectrometer [3]. The general scaling properties of local $\nabla $T$_{e}$ are presented and the results are compared with SHAx datasets; overall confinement changing is analyzed relying both on T$_{e}$ and n$_{e}$ data. Finally, being data remapping on helical coordinates a widely used tool in SHAx analysis, limits and possibilities of this technique for DAX states are discussed. \\[4pt] [1] Lorenzini R. et al$.$, Nature Physics \textbf{5}, 570 - 574 (2009)\\[0pt] [2] Alfier A., Pasqualotto R., Rev. Sci. Instrum. \textbf{78}, 1 (2007)\\[0pt] [3] Bonomo F. , Rev. Sci. Instrum. \textbf{77, }10F313 (2006)
Electron Temperature features of RFP DAX states
Marco Gobbin;Lionello Marrelli;Emilio Martines;
2011
Abstract
RFP states characterized by the presence of an hot helical structure in the plasma core have shown a significative improvement in the plasma performances. In this work we focused on DAX (Double AXis) states, in which the hot island is surrounded by a separatrix and does not cross the plasma centroid. These states, with respect to SHAx --or Single Helical Axis, [1]- , show smaller thermal structures, but the $\nabla $T$_{e}$ strength suggests a drastic local reduction of energy transport. The analysis relies on data obtained by the Main Thomson Scattering [2] and by the multichord double filter SXR spectrometer [3]. The general scaling properties of local $\nabla $T$_{e}$ are presented and the results are compared with SHAx datasets; overall confinement changing is analyzed relying both on T$_{e}$ and n$_{e}$ data. Finally, being data remapping on helical coordinates a widely used tool in SHAx analysis, limits and possibilities of this technique for DAX states are discussed. \\[4pt] [1] Lorenzini R. et al$.$, Nature Physics \textbf{5}, 570 - 574 (2009)\\[0pt] [2] Alfier A., Pasqualotto R., Rev. Sci. Instrum. \textbf{78}, 1 (2007)\\[0pt] [3] Bonomo F. , Rev. Sci. Instrum. \textbf{77, }10F313 (2006)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
