Local transport measurements during auxiliary heating in TFTR

Local heat and momentum transport is analyzed in beam-heated steady-state TFTR plasmas using measured profiles for temperature and rotation speed over a wide range of plasma conditions. As heating power is increased in high-recycling 'L-mode' plasmas, the thermal diffusivities χ_i(r) and χ_e(r) are found to increase strongly with temperature throughout the plasma confinement zone. Both chi_i and chi_e decrease with increasing plasma current in steady state L-mode plasmas. Dedicated major-radius and aspect ratio scaling experiments show that the global confinement time τ_E has a strong dependence on major radius and a weak dependence on minor radius in L-mode plasmas, τ_E ∝ R^{approximately 1.6} a^{approximately 0}. Kadomtsev dimensionless scaling of the ohmic τ_E obtained in Alcator C and PLT to TFTR at constant n̄_e/B_T^1.6, q_cyl, and a/R underpredicts τ_E by about a factor of two, possibly due to variations in L_n(e)/a. Ion heat and momentum transport in low-recycling TFTR 'supershot' plasmas shows an inverse dependence on temperature. Several independent measurements of radial-particle transport indicate diffusivities of order ≲0.1 m²/s for energetic ions (approximately 30 keV → MeV), an order of magnitude less than the observed thermal transport rates.