arXiv:2511.15024v1 Announce Type: new
Abstract: This paper investigates the impact of edge turbulence spreading on broadening the heat flux width in Ohmic-plasma approaching the density limit of the J-TEXT tokamak. At the plasma edge, the EXB shear flow collapses while turbulence transport and spreading enhances significantly when approaching the density limit. The heat flux width increases with normalized density. An energy production ratio model is used to quantify the contribution of edge turbulence spreading to the origin of the SOL turbulence. Experimental data show that the energy production ratio is much larger than 1, indicating that turbulence spreading at separatrix is the origin of the SOL turbulence. The heat flux widths increase with edge turbulence spreading as well as the energy production ratio. The impact of blob-induced transport on the heat flux width is investigated in detail. Especially, the average blob-induced spreading is about 81% of the total edge spreading in the high-density scenario. Blobs with larger radial scales enhance edge spreading into the SOL, thus dominating the SOL turbulence and consequently broadening the heat flux width. These results suggest that edge turbulence spreading plays a crucial role in broadening the heat flux width as plasma approaches the density limit.