3D effects of neon injection positions on the toroidally symmetric/asymmetric heat flux distribution on EAST

Abstract

The heat flux deposition on the divertor targets with neon impurity injection on EAST has been investigated by the three-dimensional (3D) edge transport code EMC3-EIRENE. Impact of the different poloidal neon injection positions on heat flux deposition has been studied. It is found that neon impurity injected at the in-and out-board divertors (i.e. strike points) leads to the toroidally asymmetric distributions of heat load on the in-and out-board targets, respectively. However, the neon gas puffing at the upstream shows a toroidally symmetric distribution of heat load. The 3D effects of the neon radiation on the heat load have been investigated with the help of a field line tracing technique, which indicates that neon impurity injected near the strike point can radiate more power and result in a lower heat load compared with the upstream neon injection. In order to further verify the asymmetric distribution of heat load, two impurity injection locations away from the strike points at the divertor are investigated, which shows the symmetric distribution of heat load as the upstream neon injection.

EMC3–EIRENE simulations of neon impurity seeding effects on heat flux distribution on CFETR

“…The sputtering of divertor targets has not been taken into account as references [35,36] in order to purely study external impurity gas puffing effects on heat flux control and also to save the computational resource. For the studied neon gas puffing scenarios below, the impurity recycling coefficient is assumed as 0.99 due to the low chemical activity of neon [17,20,21]. The injection energy of neon gas impurity (∼0.04 eV) and the cosine angular distribution of seeded neon velocity along the injection direction are used in the modelling.…”

“…In the previous 3D modelling of neon impurity seeding on EAST [20,21], the toroidally asymmetric distributions of heat loads can be obtained for neon injections near the strike points with an adequate injection rate. For the present modelling of CFETR, besides the injection near the strike point (GP3), the other injected positions of GP0-GP2 also show a toroidally asymmetric pattern of heat loads on the outboard divertor targets.…”

“…For the present modelling of CFETR, besides the injection near the strike point (GP3), the other injected positions of GP0-GP2 also show a toroidally asymmetric pattern of heat loads on the outboard divertor targets. According to EAST simulations [20,21], it is found that the emergence of the asymmetric heat load profile is mainly associated with the neon-induced energy loss, which is proportional to the electron density and neon impurity density. The modelling of the heat load profile for low and high n e has been performed on EAST [20,21].…”

“…According to EAST simulations [20,21], it is found that the emergence of the asymmetric heat load profile is mainly associated with the neon-induced energy loss, which is proportional to the electron density and neon impurity density. The modelling of the heat load profile for low and high n e has been performed on EAST [20,21]. At a low n e , a high neon injection rate is necessary to induce the asymmetric profile of heat loads.…”

“…The toroidally asymmetric and symmetric features of divertor heat loads on Alcator C-Mod and LHD have been well captured by the three-dimensional (3D) edge transport code EMC3-EIRENE [18,19], which are attributed to different recycling behaviours for nitrogen (low recycling) and neon (high recycling), respectively. On the other hand, studies on impacts of neon injection positions on heat flux distribution have been accomplished for EAST tokamak, which reveals that neon impurity injections around the strike points cause a toroidally asymmetric heat load distribution [20,21]. This is due to the inhomogeneous spatial distributions of neon impurity density and power dissipation.…”