Modeling of plasma beta effects on the island divertor transport in the standard configuration of W7-X

Abstract

The influence of plasma beta effects on the edge plasma transport in the Wendelstein 7-X standard configuration is studied systematically by using EMC3-EIRENE combined with a 3D equilibrium code named HINT. The magnetic topology changes induced by plasma beta effects are significantly reflected in plasma transport behaviors and heat flux patterns on divertor targets. After validating the modeling strategy by comparisons with experimental data, the extended simulations for high performance plasmas show that the threshold separatrix density for accessing the power detachment is reduced in higher beta plasmas. Compared with the vacuum field case, the impurity radiation distributions with finite beta effects are modified in the magnetic island region. The divertor heat flux is distributed more evenly along the toroidal direction on the strike line at the vertical target. The strike line on the horizontal target moves towards the pumping gap with an increase in the plasma beta. In addition, the different pressure profiles with the same central beta also result in a modified heat flux pattern on the divertor targets.

Analysis of the neutral fluxes in the divertor region of Wendelstein 7-X under attached and detached conditions using EMC3-EIRENE

“…By using the vacuum approximation for the magnetic equilibrium, the effect of plasma currents and high β effects are not included although they influence the plasma as shown in [19]. In [20] it has been shown that these high β effects are moderate for limited heating powers which are used in the presented work. Besides, the effects of drift flows which cause an asymmetry in the plasma between the upper and lower parts of the modules [21,22] is not implemented in the current version of EMC3-EIRENE.…”