NEUTRAL BEAM HEATING EXPERIMENTS ON PDX AND PLT

Abstract

Results are presented from studies of intensely beam heated plasmas in the PDX and PLT tokamaks. PDX has established that the ion heating quality factor ni = ne δTi/Pabs cm-3 keV/MW, where Pabs refers to absorbed beam power, is approximately the same for the near perpendicular injection of PDX as for the tangential injection geometry of PLT. The comparison however must be made at similar plasma currents, as ni is found to depend on Ip. Electron heating on PDX and a “clean” PLT is quite similar at ~ 0.5 eV/kW for medium densities of ~ 3–4 · 1013 cm-3 and moderate beam power. We have achieved a poloidal βθ ≈ 1.7 on PDX giving βθ ≈ 0.5 R/a at q(a) = 7.5. Initial results in low-q discharges appear promising, giving βT = 1.3–1.4% with 1.9 MW of absorbed beam power.