Improved electron and deuterium energy and particle confinement in the presence of low-Z impurities have been observed in many tokamaks under various experimental conditions. Peaked electron density profiles have been obtained in the Frascati Tokamak Upgrade (FTU) ohmic plasmas where a high concentration of lithium has been detected following the installation of a Liquid Lithium Limiter (LLL). This paper presents the results of a gyrokinetic study on the effects of lithium and other low-Z impurities on the linear stability of deuterium and electron temperature driven modes and their associated fluxes for plasma parameters such as those found in the core of LLL-FTU plasmas. Simulations show that a lithium concentration in excess of nLi/ne= 15%, as estimated in the initial phase of a reference FTU discharge, is found to have a strong stabilizing effect on the TEM and high-frequency ETG modes. A significant stabilization of the electron driven modes can still be observed when the lithium concentration is reduced to 3%. In the presence of a significant impurity concentration (nLi/ne= 3-15%) the long wavelength ITG modes drive an inward electron and deuterium flux and outward lithium flux. This process may lead eventually to an increased electron and deuterium density peaking and a reduced Zeff(lithium density below nLi/ne= 1%). © 2011 IAEA, Vienna.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Condensed Matter Physics
Romanelli, M., Szepesi, G., Peeters, A. G., Apicella, M. L., Marinucci, M., Mazzotta, C., ... Frigione, D. (2011). Linear microstability analysis of a low-Z impurity doped tokamak plasma. Nuclear Fusion, 51(10), -. . https://doi.org/10.1088/0029-5515/51/10/103008