Transport effects of low (m,n) MHD modes on TFTR supershots
- Wisconsin Univ., Madison, WI (United States)
- Princeton Univ., NJ (United States). Plasma Physics Lab.; and others
Supershots in TFTR often suffer a performance deterioration characterized by a gradual decrease of the D-D fusion neutron yield and plasma stored energy after several hundred milliseconds of auxiliary heating. The correlation between this performance deterioration and the development of low m (the poloidal mode number), n (the toroidal mode number) MHD modes is studied through shot-to-shot comparisons and statistical data analyses. A good correlation is observed between performance deterioration and the appearance of strong 3/2 and 4/3 macroscopic modes (magnetic islands) in small major radius plasmas (R = 2.45 m). The magnetic island structures are observed using Mirnov and ECE diagnostics. The measured T{sub e} T{sub i} and n{sub e}, profiles show that development of the islands corresponds to a nearly constant decrement of these quantities over the core region r < r{sub s}. where r{sub s} is the mode rational surface, on a transport time scale (t > {tau}{sub E}). The observed energy deterioration scaling, {delta}W/W {approximately}w/a, where w is the magnetic island width, agrees with both a local transport model and predictive numerical simulations. For larger major radius plasmas (R = 2.52, 2.60 m), a continuous increase of edge recycling rate during the neutral beam injection phase seems to have a larger effect on the performance deterioration than does the MHD.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 10189890
- Report Number(s):
- PPPL-2941; ON: DE94001717; TRN: 93:025570
- Resource Relation:
- Other Information: PBD: Oct 1993
- Country of Publication:
- United States
- Language:
- English
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