W W Heidbrink et al 2009 Plasma Phys. Control. Fusion 51 125001 doi:10.1088/0741-3335/51/12/125001
W W Heidbrink1, M Murakami2, J M Park2, C C Petty3, M A Van Zeeland3, J H Yu4 and G R McKee5
Show affiliationsThe DIII-D tokamak is equipped with neutral beam sources that inject in four different directions; in addition, the plasma can be moved up or down to compare off-axis with on-axis injection. Fast-ion data for eight different conditions have been obtained: co/counter, near-tangential/near-perpendicular and on-axis/off-axis. Neutron measurements during short beam pulses assess prompt and delayed losses under low-power conditions. As expected, co-injection has fewer losses than counter, tangential fewer than perpendicular and on-axis fewer than off-axis; the differences are greater at low current than at higher current. The helicity of the magnetic field has a weak effect on the overall confinement. Fast-ion Dα (FIDA) and neutron measurements diagnose the confinement at higher power. The basic trends are the same as in low-power plasmas but, even in plasmas without long wavelength Alfvén modes or other MHD, discrepancies with theory are observed, especially in higher temperature plasmas. At modest temperature, two-dimensional images of the FIDA light are in good agreement with the simulations for both on-axis and off-axis injection. Discrepancies with theory are more pronounced at low fast-ion energy and at high plasma temperature, suggesting that fast-ion transport by microturbulence is responsible for the anomalies.
52.55.Fa Tokamaks, spherical tokamaks
28.52.Cx Fueling, heating and ignition
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
Issue 12 (December 2009)
Received 6 May 2009, in final form 3 September 2009
Published 29 October 2009
W W Heidbrink et al 2009 Plasma Phys. Control. Fusion 51 125001
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