Mitigation of divertor heat flux by high-frequency ELM pacing
with non-fuel pellet injection in DIII-D Authors: A. Bortolon, R. Maingi, D.K. Mansfield, A.
Nagy, A.L. Roquemore, R. Lunsford, and R. Nazikian
Abstract:
Experiments have been conducted on DIII-D investigating high
repetition rate injection of non-fuel pellets as a tool for pacing
Edge Localized Modes (ELMs) and mitigating their transient divertor
heat loads. Effective ELM pacing was obtained with injection of Li
granules in different H-mode scenarios, at frequencies 3-5 times
larger than the natural ELM frequency, with subsequent reduction of
strike-point heat flux [Bortolon et al, Nucl. Fus., 56,
056008, 2016]. However, in scenarios with high pedestal density (~6
×)
,
the magnitude of granule triggered ELMs shows a broad
distribution, in terms of stored energy loss and peak heat flux,
challenging the effectiveness of ELM mitigation. Furthermore,
transient heat-flux deposition correlated with granule
injections was observed far from the strike-points. Field line
tracing suggest this phenomenon to be consistent with particle
loss into the mid-plane far scrape-off layer, at toroidal
location of the granule injection.
Submitted to: Nuclear Materials and Energy
_________________________________________________________________________________________________
Download PPPL-53631.7 MB (22 pp)
_________________________________________________________________________________________________
)