ICRF power deposition studies using ECE diagnostics on Alcator C-Mod
- MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
ICRF provides Alcator C-Mod with up to 3.5 MW of power at 80 MHz using two double-strap antennas. By varying the magnetic field and the mix of ion species, a variety of heating regimes have been studied. To investigate electron heating regimes, mixtures of {sup 3}He and H were used in plasmas at 6.5T. Efficient ({lt}80{percent}) direct electron heating has been observed in this scenario and is attributed to mode conversion to the ion Bernstein wave (IBW). Measurements of the mode conversion power deposition using a nine channel grating polychromator (GPC) indicate that the IBW damping can be very strong, with central power densities {gt}25MW/m{sup 3} and FWHM widths of {approx}0.2a. The presence of {gt}8{percent} deuterium {open_quotes}impurity{close_quotes} in these plasmas is shown to significantly broaden the power deposition profiles. The GPC has also been used to study the heating mechanisms in the two standard C-Mod heating scenarios: D(H) and D({sup 3}He) minority heating at 5.3T and 7.9T respectively. Mode conversion can provide a significant fraction of the heating in D({sup 3}He) plasmas, with 60{percent} efficiency and profiles which are peaked well off axis (r/a{approx}0.6) at the highest {sup 3}He concentrations (n{sub 3{sub He}}/n{sub e}{approx}0.2). Data from D(H) experiments illustrate techniques to measure minority ion tails using electron temperature dynamics. In addition, evidence is presented for D(H) mode conversion heating at high hydrogen concentration. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 580243
- Report Number(s):
- CONF-9704102-; ISSN 0094-243X; TRN: 98:004076
- Journal Information:
- AIP Conference Proceedings, Vol. 403, Issue 1; Conference: 12. topical conference on radio frequency power in plasmas, Savannah, GA (United States), 1-3 Apr 1997; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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