Divertor heat flux profiles in negative triangularity DIII-D discharges
Abstract
L-mode discharges with negative upper triangularity (δu) shape in DIII-D exhibited wider scrape-off layer (SOL) power fall off lengths (λq) compared to H-mode discharges with similar shaping. Lower single null diverted discharges with negative upper triangularity and near zero lower triangularity were developed in DIII-D at plasma current Ip=900kA with neutral beam (PNBI=4-13MW) and electron cyclotron heating (PECH=1.5 MW). SOL power fall-off lengths were derived from upstream Thomson scattering profiles and divertor infrared thermography. The inter-ELM λq measured in a negative upper triangularity (δu ∼ -0.2) H-mode discharge was comparable with those measured in H-mode discharges with positive δu. The SOL power fall off length in L-mode discharges with δu ∼ -0.4 was up to 50 % larger than in the similarly-shaped H-mode plasma. λq in negative triangularity L-mode discharges was reduced when compared to L-mode plasmas in positive triangularity at lower injected power and to multi-machine L-mode scaling. 2D transport modeling with the SOLPS-ITER code is underway to estimate the change in edge transport coefficients between negative triangularity L and H-mode discharges and their effect on divertor plasma.
Work supported by US DOE under DE-AC52-07NA27344, DE-FC02-04ER54698.- Publication:
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APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- 2020
- Bibcode:
- 2020APS..DPPG19002S