Scaling Laws of Heat Flux Width in the HL-2A Closed Divertor Tokamak

Abstract

The scaling law of the divertor heat flux width is one of the key topics of magnetic confinement fusion, which is almost inversely proportional to the poloidal magnetic field on some opened divertor tokamaks. This paper focuses on the scaling laws of the closed divertor heat flux width in the HL-2A tokamak under different discharge conditions, such as the Ohmic, L- and H-modes. The results indicate that there are basic similarities of the scaling laws of the heat flux width between the opened and closed divertors. However, a larger spreading width in the private flux region was found, which is relevant to a small expansion factor of the magnetic flux in the closed divertor.

Facilitated core-edge integration through divertor nitrogen seeding in the HL-2A tokamak

“…Detachment experiments in Ohmic [38], L-mode [39] and H-mode [40,41] discharges have been performed on the HL-2A tokamak, which has a very closed divertor structure and a larger S-factor in the PFR compared to open divertors [42]. This study reveals pronounced H-mode detachment with confinement sustainment on HL-2A through the divertor nitrogen seeding, and the underlying physics is discussed, which highlights several points as follows: (1) the closed divertor facilitates the detachment due to its efficient particle containment effect that favors the achievement of high divertor neutral pressure; (2) it could diminish the ELM amplitude by altering the pedestal structure through the divertor nitrogen seeding; (3) it induced a positive feedback mechanism of ion temperature improvement during the detachment and revealed the important role of E × B shear in this process.…”

How turbulent transport broadens the heat flux width: local SOL production or edge turbulence spreading?

“…Concern for this issue drives measurements and predictions of the heat flux width λ q [1]. The magnitude and scaling trends of λ q are of great interest [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Specifically, scaling laws of λ q in limited Ohmic-plasma from multiple machines have been studied in the International Tokamak Physics Activity from 2013 to 2016 [7][8][9].…”