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T. E. Evans, P. L. Taylor, A. G. Kellman,
P. Parks, D. A. Humphreys, M. J. Schaffer,
A. W. Hyatt, R. L. Lee, J. A. Leuer
General Atomics, P.O. Box 85608, San Diego, California, U.S.A.
D. G. Whyte, S. C. Luckhardt, D. Gray,
J. Zhang
University of California, San Diego, La Jolla, California, U.S.A.
CompX, Del Mar, California, U.S.A.
T. Jernigan, L. R. Baylor
Oak Ridge National Lasboratory, Oak Ridge, Tennessee, U.S.A.
Abstract. Prompt runaway electron bursts, generated by rapidly cooling DIII-D
plasmas with argon ``killer'' pellets, are used to test a recent knock-on
avalanche theory describing the growth of multi-MeV runaway electron currents
during disruptions in tokamaks. Runaway current amplitudes, observed during
some but not all DIII-D current quenches, are consistent with growth rates
predicted by the theory assuming a pre-current quench runaway electron density
of approximately
1015m- 3. Argon ``killer'' pellet modeling yields
runaway densities of between
1015 - 1015m- 3 in these
discharges. Although knock-on avalanching appears to agree rather well with
the measurements, relatively small avalanche amplification factors combined
with uncertainties in the spatial distribution of pellet mass and cooling
rates make it difficult to unambiguously confirm the proposed theory with
existing data. Additional measurements are proposed which should enable us to
definitively test the theory.
IAEA 2001
