Tokamak and RFP ignition requirements

A plasma model is applied to calculate numerically transport-confinement (n tau /sub E/) requirements and steady-state operation points for both the reversed field pinch (RFP) and tokamak. The CIT tokamak and RFP ignition conditions are examined. Physics differences between RFP and tokamaks and their consequences for a DT ignition machine are discussed. The ignition RFP, compared to a tokamak, has many physics advantages. These advantages, coupled with important engineering advantages translate into significant cost reductions for both ignition and power reactor. The primary drawback of the RFP is the uncertainty that the present confinement scaling will extrapolate to reactor regimes. The 4-MA ZTH was expected to extend the n tau /sub E/ transport scaling data three orders of magnitude above ZT-40 M results, and if the present scaling held, to achieve a DT-equivalent scientific energy breakeven, Q=1. A base-case RFP ignition point is identified with a plasma current of 8.1 MA and no auxiliary heating.<>