Status of the ZT-40M RFP Experimental Program

The present status of research on the ZT-40M Reversed-Field Pinch (RFP) will be described. RFP discharges have been sustained for times (27 ms) >> the classical resistive diffusion time, implying the existence of a flux-sustainment mechanism (“dynamo”). This mechanism opens the possibility for a steady-state RFP reactor utilizing a unique form of non-inductive current drive. T_e > 500 eV has been obtained for 400 kA aischarges with ∼ 4 × 10¹⁹ m⁻³. Total energy confinement time τ_E has reached 0.7 ms with a Lawson parameter of 5 × 10¹⁶ m⁻³ s for discharges with = 8×10¹⁹ m⁻³ and T_e = 330 eV at a plasma current of 330 kA and 0.33 T total confining field at the wall. Reactor-like β_θ ∼ 10–20% is routinely obtained for plasma currents from 60–400 kA (β ∼ β_θ/2). Scaling of τ_E ∼ I^(2.2±0.4) is found, more than adequate for a compact RFP reactor.