Abstract Details
Abstracts
Author: Valerie Izzo
Requested Type: Poster
Submitted: 2017-03-17 16:47:55
Co-authors: P.B. Parks
Contact Info:
University of California San Diego
9500 Gilman Dr
San Diego , California 92093
United States
Abstract Text:
MHD simulations indicate several promising features for a novel disruption mitigation strategy that aims to deliver a radiating payload directly to the core while minimally perturbing the edge plasma. In practice, this would be accomplished by the so-called “shell pellet” method, which encloses the payload in a low-Z shell that slowly ablates then breaks open in the center of the plasma. Disruption mitigation for ITER must simultaneously meet several criteria for thermal and mechanical loads and runaway electron avoidance, some of which are in tension with one another. For instance, prevention of a runaway electron avalanche may be possible if complete flux surface destruction during the thermal quench de-confines the primary runaway electron population before the secondary avalanche can ensue. But, the same flux surface destruction that allows runaway electrons to follow open field lines to the wall may just as easily conduct electron heat to the wall.
In the simulations, the high-Z payload is assumed to be delivered directly to the core. The strong core cooling produces an “inside-out” thermal quench that propagates toward the edge, and results in an annular current profile and an increase in total current due to dropping inductance during the thermal quench. Importantly, the flux surfaces also break up from the outside in, with the outermost surfaces remaining intact until the end of the thermal quench, resulting in a very high radiated energy fraction. Nonetheless, once the last closed flux surface is broken, a very rapid loss of test-particle runaway electrons is observed. The current quench proceeds in two phases, initially rapidly then more slowly, as the current profile redistributes. The benefits of this disruption mitigation approach over injection of impurities in the edge plasma will be discussed.
Work supported by DOE Office of Fusion Energy Sciences under contract Nos. DE-FG02-95ER54309, DE-FC02-01ER25455, and DE-FC02-04ER546
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