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AbstractAbstract
[en] Particle transport in multi-pellet fueled JET plasmas in being examined to help evaluate density profile behavior in ITER. Preliminary results of the JET analysis were reported at the IAEA Technical Committee Meeting on Pellets in October 1988. In sawtooth free JET discharges, the density profile evolution after injection of pellets can be modeled with the neoclassical Ware pinch and a diffusion coefficient that is small in the plasma core and increased sharply in the vicinity of the q = 2 surface. This model is applicable to both ohmic and central ICRF heated discharges. Some of the auxiliary heated plasmas show a more rapid central density decay that appears to be related to MHD activity observed in soft x-ray signals. In these discharges the density profile evolution can be modeled with a temperature dependent diffusion coefficient and the neoclassical Ware pinch. There is a strong correlation between the inferred local particle and heat transport coefficients in all discharges. Plasmas with non-central pellet penetration show no significant density peaking, consistent with the small Ware pinch term. These results appear to conflict with those reported for ASDEX. There it was found that sustained pellet injection during neutral beam and ICRF heating, with pellet penetration of only half the plasma radius, led to markedly peaked electron density profiles as well as high edge recycling, reduced sawtooth activity, central impurity radiation, enhanced density limit, and improved global energy confinement. Thus, the implications of these results for ITER are still highly speculative because of the lack of knowledge about scaling with machine parameters. The JET results suggest that relatively deep fueling may be required to significantly influence the density profile shape, while the ASDEX results imply that partial penetration may be sufficient. 20 figs
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1989; 23 p; IAEA technical committee meeting on H mode physics; Gut Ising, Upper Bavaria (Germany, F.R.); 20-22 Mar 1989; Available from NTIS, PC A03/MF A01 - OSTI; 1 as DE89008730; Portions of this document are illegible in microfiche products.
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