Recent advances in EAST physics experiments in support of steady-state operation for ITER and CFETR

Abstract

The recent EAST experimental progress since the last IAEA FEC in 2016 is presented. First demonstration of >100 seconds time scale long-pulse steady-state scenario with a good plasma performance (H98(y2) ~ 1.1) and a good control of impurity and heat exhaust with the tungsten divertor has been successfully achieved on EAST using the pure RF power heating and current drive. The extended operation regimes have been obtained (βP~2.5 & βN~1.9 of using RF&NB and βP~1.9 & βN~1.5). High bootstrap current fraction up to 47% was achieved with q95~6.0-7.0. The interaction effect between the ECH and two LHW systems has been investigated for enhanced current drive and improved confinement quality. ELM suppression using the n= 2 RMPs has been achieved at q95 (≈ 3.2-3.7) with standard type-I ELMy H-mode operational window in EAST. Reduction of the peak heat flux on the divertor was demonstrated using the active radiation feedback control. An increase in the total heating power and improvement of the plasma confinement are expected using a 0-D model prediction for higher bootstrap fraction. Towards long pulse, high bootstrap current fraction operation, a new lower ITER-like tungsten divertor with active watercooling will be installed, together with further increase and improvement of heating and current drive capability.

Dependence of upstream SOL density shoulder on divertor neutral pressure observed in L-mode and H-mode plasmas in the EAST superconducting tokamak

“…The experiments were performed in the EAST device [27], with the setups of the key diagnostics shown in figure 1. EAST is a fully superconducting tokamak with major and minor radii: R 0 = 1.88 m and a = 0.45 m, respectively.…”

A brief summary of tungsten technology development in Korea

“…The brazing process consists of five steps: (1) a nickel plate of a thickness of 5 µm was plated on tungsten prior to the brazing process for the improvement of wettability and bonding strength of the brazing filler, and a heat treatment at a temperature of 600 °C for an hour was followed, which enhanced the quality of the nickel plating; (2) W was brazed onto CuCrZr at 980 °C for 30 min in vacuum; (3) fast cooling from 980 to 400 °C was followed; (4) the aging treatment for CuCrZr was carried out for ~ 180 min at 470 °C; (5) cool down to the room temperature [14]. Figure 1 shows the waveform of the W/Cu/CuCrZr brazing process.…”

“…The axially symmetric divertor experiment (ASDEX) upgrade (AUG) has changed the inner wall to tungsten coated graphite tiles [2,3]. The experimental advanced superconducting tokamak (EAST) has a full tungsten divertor since 2018 and tungsten environment in steady-state tokamak (WEST) started with several tungsten monoblock fingers and tungsten coated graphite blocks [4,5].…”

Plasma–tungsten interactions in experimental advanced superconducting tokamak (EAST)

“…ASIPP developed a batch manufacturing technology for ITER-like water-cooled full W-PFC which employs copper alloy (CuCrZr) as a heat sink material and the hot isostatic pressing (HIP) method to join the W-PFM and the CuCrZr heat sink together [6]. Therewith ASIPP upgraded the EAST upper divertor from the bolted graphite tile PFC [7] into the ITER-like watercooled full W-PFC in 2014, and the W divertor came into service successfully [8][9][10][11]. Fully non-inductive steadystate H-mode plasmas (H 98, y2 ~ 1.1) were achieved with a duration of more than 60 s in 2016 experimental campaign [10] and further extended to ~ 100 s in 2017 campaign with a good control of impurity and heat exhaust benefiting from the upper W divertor [11].…”

“…Therewith ASIPP upgraded the EAST upper divertor from the bolted graphite tile PFC [7] into the ITER-like watercooled full W-PFC in 2014, and the W divertor came into service successfully [8][9][10][11]. Fully non-inductive steadystate H-mode plasmas (H 98, y2 ~ 1.1) were achieved with a duration of more than 60 s in 2016 experimental campaign [10] and further extended to ~ 100 s in 2017 campaign with a good control of impurity and heat exhaust benefiting from the upper W divertor [11]. A new lower W divertor is designed [12] and will replace the existing graphite divertor in 2020.…”