Comparison of dynamical features between the fast H-L and the H-I-L transition for EAST RF-heated plasmas

Abstract

In this paper, a comparison of dynamical features between the fast H-L and the H-I-L transition, which can be identified by the intermediate phase, or ‘I-phase’, has been made for radio-frequency (RF) heated deuterium plasmas in EAST. The fast H-L transition is characterized by a rapid release of stored energy during the transition transient, while the H-I-L transition exhibits a ‘soft’ H-mode termination. One important distinction between the transitions has been observed by dedicated probe measurements slightly inside the separatrix, with respect to the radial gradient of the floating potential, which corresponds to the E×B flow and/or the electron temperature gradient. The potential gradient inside the separatrix oscillates and persists during the stationary I-phase, and shows a larger amplitude than that before the fast H-L transition. The reduction of the gradient leads to the final transition to the L-mode for both the fast H-L and the H-I-L transition. These findings indicate that the mean E×B flow shear and/or edge electron temperature gradient play a critical role underlying the H-L transition physics. In addition, the back transition in EAST is found to be sensitive to magnetic configuration, where the vertical configuration, i.e., inner strike-point located at vertical target, favours access to the H-I-L transition, while the horizontal shape facilitates achievement of the fast H-L transition. The divertor recycling level normalized to electron density is higher before the fast H-L transition, as compared to that before the I-phase, which strongly suggest that the density of the recycled neutrals is an important ingredient in determining the back transition behaviour.

Soft H-L back transitions by applying resonant magnetic perturbations in the low q 95 EAST plasmas

“…Under marginal power injection, an increased plasma density before the H-L transition is also observed in the TJ-II stellarator [9]. Soft H-L transitions are observed when the auxiliary heating power is at the H-mode power threshold in EAST [20], while increased plasma density before the H-L transitions is also found sometimes [21]. Thus, the realization of soft H-L transitions by switching off the auxiliary heating is not a robust method, since the plasma density may be out of control before the confinement regime transition.…”

A Novel Approach for Rapid Material Library Generation Using Laser‐Remelting

“…The supporting CALPHAD (=CALculation of PHAse Diagrams) calculations were performed using the Thermo‐Calc Software (Version 2022a) and the thermodynamic database TCHEA4. [ 48,49 ]…”

Highly efficient photosynthesis of hydrogen peroxide by a stable Zr(iv)-based MOF with a diamino-functionalized ligand

“…In the past few decades, a wide range of research studies into the photocatalytic production of H 2 O 2 have been carried out, and catalysts involving bismuth vanadate, 5,6 metal oxide and/or their complexes, [7][8][9][10][11][12] graphitic carbon nitride, 13,14 cadmium sulphide, 15,16 metal-organic frameworks (MOFs) [17][18][19][20][21][22][23][24][25][26][27][28][29][30] and covalent organic frameworks [31][32][33][34][35] have been reported. Among them, MOFs have attracted special attention not only due to their porosity, large surface area and crystalline nature, but also due to the ready functionalization of their metal nodes and organic ligands.…”