Previous analysis of impurity transport in the RFX device, where a thick passive conducting shell was used for the stabilisation of the MHD modes, had shown a highly anomalous diffusion coefficient of the order of 10-20m 2/s in the central plasma (r/a<0.8), decreasing to about 1-2 m2/s at the edge, with a pinch velocity changing from outward to inward at r/a ∼ 0.8. This paper presents the carbon and oxygen transport investigations performed on the new version of the machine, RFX-mod, where a set of 4x48 saddle external coils allows a better control of the radial magnetic field at the edge resulting in a significant reduction of the amplitude of the MHD modes (about an order of magnitude) and of the heat transport. The impurity diffusion coefficient and the pinch velocity have been determined in such a way to best reproduce with a 1-dim Collisional-Radiative (CR) model all the available spectroscopic data. The conclusion is that the same transport coefficients found for the old RFX allow the best experimental data simulation in spite of the lower magnetic fluctuation level. The impurity transport coefficients determined in this way have also been compared with those calculated taking into account classical particle collisions and diffusion in a stochastic magnetic field in a large part of the plasma core region (up to r/a=0.9): though much lower in the core, the diffusion coefficient calculated according to the theory has a similar shape if compared with the empirical one. The simulation of spectroscopic data requires that the convective velocity changes direction more internally than predicted by the theory.
|Publication status||Published - 2006|
|Event||33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006 - , Italy|
Duration: 1 Jan 2006 → …
|Conference||33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006|
|Period||1/1/06 → …|
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
Carraro, L., Gazza, E., Lorenzini, R., Mattioli, M., Puiatti, M. E., Scarin, P., ... Zaniol, B. (2006). Effects on impurity transport of the active control of the magnetic boundary in RFX-mod. Paper presented at 33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006, Italy.