First attempt to quantify W7-X island divertor plasma by local experiment-model comparison

Abstract

As a complement to our recent work [1], which focused on understanding the basic detachment physics and general experimental and numerical trends observed in the W7-X island divertor, this paper compares EMC3-Eirene simulation results with different local diagnostics, including IR cameras, Langmuir probes, H α -cameras, and Thomson scattering. The main purposes are to (1) justify the simulation setup in the previous work, (2) identify the application limitations of the current EMC3-Eirene model, (3) verify the consistency of different diagnostics, and (4) isolate the main geometric and physical effects that need to be prioritized in further developing the EMC3-Eirene code and improving diagnostic capabilities. It turns out that the current version of the EMC3-Eirene code (without drifts) is not yet able to quantitatively reproduce all selected local measurements simultaneously under the current experimental conditions (in particular, the existence of error fields). Nevertheless, it can be shown that within a reasonable range of variation in magnetic configuration, cross-field transport, and SOL plasma state in the modeling, a region of overlap between the numerical results and the local measurements can be established. More accurate model-experiment comparisons will require clarification of error fields, implementation of drifts in EMC3, and improvement of diagnostic capabilities.

Plasma radiation behavior approaching high-radiation scenarios in W7-X

“…As a result, the radiation zone shifts radially inward (see figure 4(h), which follows an increase in f rad, core and leads to a small reduction in stored energy (10%-15%). This phenomenon demonstrates the self-regulating capability of the W7-X divertor plasma, which is qualitatively consistent with the recent simulation results using the EMC3-Eirene code [52]. However, the asymmetric radiation feature obtained with bolometer tomography (figure 4) differs from the simulation results.…”

“…More accurate simulations of the W7-X plasma radiation require actually 3D modeling. However, the current version of the EMC3-Eirene code (without drifts) for 3D modeling is not yet able to quantitatively reproduce all selected local measurements simultaneously under the current experimental conditions (in particular, the existence of error fields) [52]. Some results using EMC3-Eirene code are reported in [37,51] and com-parisons with the bolometer results (in OP1.2a before boronisation) show qualitative agreements but also differences, especially in the asymmetric feature of the impurity radiation distribution.…”

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

“…However, impurity injection experiments during turbulence-suppressed phases show that impurity accumulation could be a challenge for long-pulse, highperformance discharges in the upcoming experimental campaigns. Besides the references already given, readers are also referred to other recent W7-X publications [60][61][62][63][64] for more examples of recent results and more detailed descriptions.…”

Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

“…It has already been used in the past to model the edge of W7-X [14][15][16][17][18][19][20][21]. While EMC3-EIRENE does captures some of the observations in experiments, especially global trends [14,16], there is still disagreement in local parameters [30].…”