DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
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Title	254: Neon SPI injection into early CQ to stunt RE formation
Name:	Nicholas Eidietis eidietis@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Disruption Mitigation	Presentation time:	Not requested
Co-Author(s):	P. Parks	ITPA Joint Experiment :	No
Description:	Inject Hi-Z (Neon) SPI immediately after the TQ of an RE-generating small argon pellet shot in order to stunt the growth of a very young RE beam. The idea here is that immediately after the TQ there is no hot thermal plasma to ionize the SPI, so the impurities will ONLY deposit within the small forming RE core, perhaps allowing the Rosenbluth density to be reached within the small volume of that RE core.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Initiate RE-producing disruption with small Ar pellets or Ar MGI into limited, low density target. After 1-2 shots to determine injection->TQ timing, inject Neon SPI at such a time that the neon will hit the plasma withing ~ 1ms after thermal quench. Observe if RE current is substantially reduced from case with no secondary injection.
Background:	It appears unlikely that any single impurity mitigation strategy will properly handle the TQ and suppress runaway electrons. As an alternative, we propose a 2-step strategy for partial RE suppression. The fundamental problem with RE suppression using just one step is that the impurities become ionized by the hot thermal plasma before they come near the core where they are needed to collisionally suppress RE production. It is possible that immediately AFTER the TQ, when there is no hot thermal plasma, a second high-Z SPI (or large pellet) injection will pass untouched through the cold thermal plasma and ONLY deposit in the newly forming RE core, creating sufficient density only in the core where it is needed to suppress further growth of the RE bea,.
Resource Requirements:	Argon pellet injector or Argon MGI, Neon SPI
Diagnostic Requirements:	neutron counters, SXR, fast camera
Analysis Requirements:	--
Other Requirements:	--