Correlation of submicron dust observed in DIII-D during plasma operation with plasma operating parameters

A database of dust events observed using the Thomson scattering systems on DIII-D has recently been expanded to incorporate over 2500 discharges over a 9-month period from 2004 to 2005 campaign. The system is sensitive to dust particles of radius ≲50 nm. Over this period of time, 5130 dust events were observed in the upper SOL region of the plasma and 4159 events in the lower divertor region. In the observation channels nearest the wall, the dust density is observed to be about 1.2 × 104 m−3 in the upper region and about 6 × 104 m−3 in the lower divertor. In both regions, the density drops sharply approaching zero at the last closed flux surface. Dust observation rate increases with increasing injected beam power in both regions. In the upper region, the observation rate increases sharply for a brief period after switching from operation with a dominant lower null to a dominant upper null. For a few shots after major disruptions, the observation rate increases slightly in the lower divertor but decreases slightly in the upper SOL.