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Languages : en
Pages : 8
Book Description
Fast waves provide an excellent tool for heating electrons and driving current in the central region of tokamak plasmas. In this paper, we report the use of centrally peaked electron heating and current drive to study transport in plasmas with negative central shear (NCS). Tokamak plasmas with NCS offer the potential of reduced energy transport and improved MHD stability properties, but will require non-inductive current drive to maintain the required current profiles. Fast waves, combined with neutral beam injection, provide the capability to change the central current density evolution and independently vary {ital T{sub e}}, and {ital T{sub i}} for transport studies in these plasmas. Electron heating also reduces the collisional heat exchange between electrons and ions and reduces the power deposition from neutral beams into electrons, thus improving the certainty in the estimate of the electron heating. The first part of this paper analyzes electron and ion heat transport in the L-mode phase of NCS plasmas as the current profile resistively evolves. The second part of the paper discusses the changes that occur in electron as well as ion energy transport in this phase of improved core confinement associated with NCS.