Description: The ignition parameter Tn/tau//sub E/ of the International Tokamak Experimental Reactor (ITER) with an aspect ratio A = 2.6, a major radius R = 5.8 m, a plasma current I/sub p/ = 22 MA, and an external toroidal field of B/sub t0/ = 5 T at R; a High Field Experimental Reactor (HFER) with A = 6.0, R = 6.0 m, I/sub p/ = 8.2 MA, and B/sub t0/ = 12.4 T; and a Spherical Torus Experimental Reactor (STER) with A = 1.2, R = 1.5 m, I/sub p/ = 22 MA, and B/sub t0/ = 0.88 T are compared using a set of presently popular empirical or semi-empirical confinement scaling expressions. Since the physics basis for these scaling expressions are not determined, the results of comparison are best suited to helping identify issues critical to furthering our understanding of tokamak confinement. In the case where the plasma pressure is limited by the Troyon beta scaling using B/sub t0/, the scaling expressions with relatively strong A-dependence, favor the HFER, while those with relatively strong I/sub p/-dependence favor the STER or suggest comparable Tn/tau//sub E/. In the case where the plasma pressure is determined by a second stability /epsilon//beta//sub p/ limit (/epsilon/ = 1/A), the projections of the T-10 Goldston, Odajima-Shimamura, and Rebut-Lallia scaling expressions are also compared. There it is found that the above STER and HFER would suffice if /epsilon//beta//sub p/ = 0.5. These varied projections highlight the uncertain I/sub p/, A and R dependencies in empirical tokamak confinement scaling, which are likely to be resolved only by tests at very low and high A. The results also indicate that whether the plasma pressure is determined by a high /epsilon//beta//sub p/ limit is critical to the viability of the HFER and the STER compared to ITER, even if the ...
Date: January 1, 1989
Creator: Peng, Y.K.M.
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