Power balance in reversed field pinch plasmas with poloidal current drive and its impact on economics of fusion reactor

Power balance in a CD (Current Drive)-assisted RFP (Reversed Field Pinch) is analyzed which utilizes poloidal current drive externally in order to reduce transport losses due to MHD-dynamo, i.e., tearing mode instability. Changes of power flow and heat conductivity are treated self-consistently by using a model which assumes that amplitudes of magnetic fluctuations decrease proportionally with the ratio of externally-driven current to dynamo-driven current. It is found that the plasma temperature reaches is beta-limit and energy confinement time increases by a factor of 3-10 of that determined by tearing instability, when 30-40% of total dynamo current is replaced by neutral-beam current and/or lower-hybrid wave current. Necessary conditions of economic competitiveness of pulsed CD-assisted RFP reactor to DC-operated tokamak reactor are also examined. (author)