Beam-ion confinement for different injection geometries

Journal Article · Thu Jan 01 00:00:00 EST 2009 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/0741-3335/51/12/125001· OSTI ID:1019002

Heidbrink, W. W. ^[1]; Murakami, Masanori ^[2]; Park, Jin Myung ^[2]; Petty, C C. ^[3]; Van Zeeland, Michael ^[4]; Yu, J. H. ^[5]; Mckee, G. R. ^[6]

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1. University of California, Irvine
2. ORNL
3. General Atomics, San Diego
4. General Atomics
5. University of California, San Diego
6. University of Wisconsin, Madison

The 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 D-alpha (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 Alfven 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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1019002
• Journal Information: Plasma Physics and Controlled Fusion, Vol. 51, Issue 12; ISSN 0741--3335
• Country of Publication: United States
• Language: English