Helium, iron, and electron particle transport and energy transport studies on the Tokamak Fusion Test Reactor

Abstract

Results from helium, iron, and electron transport studies on the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. 26, 11 ( 1984)] in L-mode and supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the supershot. The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the supershot, differences are found in the L mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of 3 larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

“…thermal helium. The measured helium diffusivity and convective velocity from an earlier helium transport study [122] were used to model the helium ash behavior in these discharges. The TRANSP modeling implied that helium ash source profile was similar to the TRANSP neutron emission profile since the energetic alpha particles were well confined.…”

Transient Transport Experiments in the CDX-U Spherical Torus

“…Perturbative transport experiments have been performed on nearly all major fusion devices over the past decade [15][16][17][18][19][20][21][22][23][24], and can offer several advantages over steady-state techniques. These include decoupling of density and temperature gradients from each other, and a decoupling of temperature and density from their gradients, with no essential degradation of the quality of the data [25].…”

Results from D—T experiments on TFTR and implications for achieving an ignited plasma

“…Local transport studies of supershots indicate that most of the improvement in confinement is associated with the reduction of ion heat conduction (Scott et al 1990a,b) and ion particle transport (Synakowski et al 1993). The transport studies also indicate a very different scaling of ion heat, χ i, and momentum, χ φ , , diffusivity with T i .…”