Energy Balance, Radiation and Stability During Rapid Plasma Termination via Impurity Pellet Injections on DIII-D

Injections of impurity {open_quotes}killer{close_quotes} pellets on DIII-D have demonstrated partial mitigation of undesirable disruption phenomena; namely reducing the convected heat loss to the wall, and the halo current`s magnitude and toroidal asymmetry. However, the appearance of a runaway electron population and large magnetic fluctuations (B/B{sub T} {approx} 1%) is coincident with the measured rapid loss of the plasma`s thermal energy ({approx}1 MJ in 1 ms) due to impurity radiation. A numerical code is developed to simulate the impurity radiation and predict the rapid plasma cooling observed. The simulation predicts two mechanisms for the generation of runaway electrons: the {open_quotes}slideaway{close_quotes} of hot tail electrons due to rapid cooling or the transport of hot electrons into the thermally collapsed plasma due to instabilities. Pressure gradients caused by the rapid non-adiabatic cooling of the impurity are identified as the probable source of these instabilities which also lead to convective heat losses. Results of a modeling effort to optimize pellet content, impurity species and cooling time for the avoidance of instabilities and runaway electrons are shown

Plasma Dynamics

Contains reports on three research projects.U.S. Department of Energy (Contract DE-ACO2-78ET-51013)National Science Foundation (Grant ECS82-13430)U.S. Air Force - Office of Scientific Research (Contract F33615-81-K-1426

Quantitative Coding and Complexity Theory of Compact Metric Spaces

Specifying a computational problem requires fixing encodings for input and output: encoding graphs as adjacency matrices, characters as integers, integers as bit strings, and vice versa. For such discrete data, the actual encoding is usually straightforward and/or complexity-theoretically inessential (up to polynomial time, say); but concerning continuous data, already real numbers naturally suggest various encodings with very different computational properties. With respect to qualitative computability, Kreitz and Weihrauch (1985) had identified ADMISSIBILITY as crucial property for 'reasonable' encodings over the Cantor space of infinite binary sequences, so-called representations [doi:10.1007/11780342_48]: For (precisely) these does the sometimes so-called MAIN THEOREM apply, characterizing continuity of functions in terms of continuous realizers. We rephrase qualitative admissibility as continuity of both the representation and its multivalued inverse, adopting from [doi:10.4115/jla.2013.5.7] a notion of sequential continuity for multifunctions. This suggests its quantitative refinement as criterion for representations suitable for complexity investigations. Higher-type complexity is captured by replacing Cantor's as ground space with Baire or any other (compact) ULTRAmetric space: a quantitative counterpart to equilogical spaces in computability [doi:10.1016/j.tcs.2003.11.012]

Plasma Dynamics

Contains reports on six research projects.National Science Foundation (Grant ECS82-00646)National Science Foundation (Grant ECS82-13485)U.S. Air Force - Office of Scientific Research (Contract F33615-81-K-1426)U.S. Air Force - Office of Scientific Research (Contract F49620-83-C-0008)U.S. Air Force - Office of Scientific Research (Contract AFOSR-84-0026)U.S. Navy - Office of Naval Research (Contract N00014-83-K-2024)Sandia National Laboratory (Contract 31-5606)Sandia National Laboratory (Contract 48-5725)U.S. Department of Energy (Contract DE-ACO2-78ET-51013)National Science Foundation (Grant ECS82-13430

Plasma Dynamics

Contains reports on eight research projects split into two sections.National Science Foundation (Grant ENG79-07047)U.S. Air Force - Office of Scientific Research (Grant AFOSR-77-3143D)U.S. Department of Energy (Contract DE-ACO2-78ET-51013)U.S. Department of Energy (Contract DE-ACO2-78ET-53073.AO02)U.S. Department of Energy (Contract DE-ACO2-78ET-53074)U.S. Department of Energy (Contract DE-ACO2-78ET-53076)U.S. Department of Energy (Contract DE-ACO2-78ET-51002

Plasma Dynamics

Contains reports on six research projects.National Science Foundation (Grant ENG79-07047)U.S. Air Force - Office of Scientific Research (Grant AFOSR77-3143D)U.S. Air Force - Office of Scientific Research (Contract AFOSR82-0063)U.S. Department of Energy (Contract DE-ACO2-78-ET-51013)U.S. Department of Energy (Contract DE-AC02-78ET-53073.A002

Plasma Dynamics

Contains reports on ten research projects divided into two sections.National Science Foundation (Grant ENG79-07047)U.S. Air Force - Office of Scientific Research (Grant AFOSR-77-3143)U.S. Department of Energy (Contract DE-ACO2-78ET51013)U.S. Department of Energy (Contract DE-ASO2-78ET53073.AO02)U.S. Department of Energy (Contract ET-78-S-02-4682)U.S. Department of Energy (Contract DE-AS02-78ET53074)U.S. Department of Energy (Contract DE-ASO2-78ET53050)U.S. Department of Energy (Contract DE-AS02-78ET51002)U.S. Department of Energy (Contract DE-ASO2-78ET53076

Plasma Dynamics

Contains reports on five research projects.U.S. Air Force - Office of Scientifc Research (Contract AFOSR 84-0026)National Science Foundation (Grant ECS 85-14517)Lawrence Livermore National Laboratory (Subcontract 6264005)National Science Foundation (Grant ECS 85-15032)U.S. Department of Energy (Contract DE-ACO2-78-ET-51013)U.S. Department of Energy (Contract DE-ACO2-ET-51013