Divertor plasma behaviors with neon seeding at different locations on EAST with ITER-like divertor

Abstract

For the problem of excessively high divertor heat flux, active impurity seeding is an effective method to radiate the plasma energy reaching the divertor and thus achieve the divertor detachment. Neon is a very effective radiation impurity on many current tokamaks, which is also a candidate species to be applied on ITER. In the EAST 2019 experimental campaign, a series of experiments were performed by seeding a mixture of neon and deuterium (Ne-D2) for detachment and core-edge-divertor integration in H-mode plasmas. The divertor partial detachment with high-confinement core plasma has been achieved by using Ne-D2 seeding in EAST with ITER-like tungsten divertor. Both the plasma stored energy and H_(98,y2)>1.1 are maintained, with the divertor electron temperature, heat flux and the surface temperature near the strike point being all significantly reduced. The differences between Ne-D2 seeding at the scrape-off layer (SOL) upstream and downstream have been experimentally investigated in detail. It is found that impurity seeding at SOL downstream is more beneficial to reducing the divertor electron temperature and peak heat flux. By comparison with experiments using divertor D2 fueling, it is further demonstrated that gas seeding in the SOL downstream will enrich more particles near the strike point, while the seeding in the SOL upstream will influence the entire outer target more evenly. Furthermore, in most of the experiments, gas seeding does not cause obvious toroidal asymmetry in the divertor plasma. However, when D2 is injected in an amount similar to that used to build the plasma, it causes the particle flux near the gas-puff to increase locally, i.e., much more than that at the toroidal location far from the gas-puff location. It is a competition between particle source and transport. When the particle source is stronger, it will naturally increase the local particles. In addition, dedicated experiments with different poloidal distances between impurity seeding and strike point on the radiation ability were carried out. Both experimental results and SOLPS simulation show that the seeding close to the strike point is more conducive to neon ionization and energy radiation.

Role of pinch in Argon impurity transport in ohmic discharges of Aditya-U Tokamak

“…On the other hand, impurities such as nitrogen, neon and argon are injected in several tokamaks including JET 7 , TEXTOR-94 13 , TFTR 14 , DIII-D 15 , ASDEX-U 16 , Aditya-U 17 , EAST 18 , KSTAR 9 , MAST 10 , T-10 11 etc. for radiative divertor cooling and heat-load reduction to the tugnsten targets 19 as well as to lower the H-mode threshold in presence of metallic walls 7 .…”

Effects of strike point location on the divertor particle and energy flux decay widths on EAST by experiment and SOLPS modeling

“…In the experiment, the plasma profiles along the OT (electron density n e,OT , ion saturation current J sat,OT , electron temperature T e,OT and parallel heat flux density q ||,OT ) are measured by divertor LP [28,29]. However, the arrangement of LP leads to poor resolution of plasma profile.…”

Relativistic atomic structure calculations of Li-like ions used for plasma diagnostic studies

“…The inclusion of relativistic and QED corrections is mandatory as it lead to better accuracy and thus more precise evaluation of line intensity ratio. Previously, ions like Ar, Ti, Fe, Ni, Kr and W were established as prominent plasma impurities in operational high temperature plasma devices such as ADITYA-U, EAST, KSTAR, JT-60 in Japan, JET in European Union, DIII-D and NSTX in USA [24][25][26][27][28][29][30][31][32][33]. At present, ITER is under construction in France as a multinational collaborative project and tungsten (W) is used as a material for divertor of tokamak where the plasma heat is quite intense [34].…”