Integrated simulation of ELM energy loss determined by pedestal MHD and SOL transport

Abstract

Abstract. An integrated simulation code TOPICS-IB based on a transport code with a stability code for the peeling-ballooning modes and a scrape-off-layer (SOL) model has been developed to clarify self-consistent effects of edge localized modes (ELMs) and SOL on the plasma performance. Experimentally observed collisionality dependence of the ELM energy loss is found to be caused by both the edge bootstrap current and the SOL transport. The bootstrap current decreases with increasing the collisionality and intensifies the magnetic shear at the pedestal region. The increase of the magnetic shear reduces the width of eigenfunctions of unstable modes, which results in the reduction of the area and the edge value near the separatrix of the ELM enhanced transport. On the other hand, when an ELM crash occurs, the energy flows into the SOL and the SOL temperature rapidly increases. The increase of the SOL temperature lowers the ELM energy loss due to the flattening of the radial edge gradient. The parallel electron heat conduction determines how the SOL temperature increases. For higher collisionality, the conduction becomes lower and the SOL electron temperature increases more. By the above two mechanisms, the ELM energy loss decreases with increasing the collisionality. The bootstrap current and the SOL transport have the major effect on the collisionality dependence.

Integrated ELM Simulation with Edge MHD Stability and Transport of SOL‐Divertor Plasmas

“…In the case A with P inped /P ped =0.21, the ELM energy loss is less than 10 % of the pedestal energy and is comparable with those in JT-60U [1]. As a reference, we add a result in the previous study [14], which indicated by A' in Fig.4. In the case A', values of τ ELM and χ max ELM are reduced half to τ ELM =200 µs and χ max ELM =100 m 2 /s, and the plasma current is reduced to I p =1.5 MA (q 95 =4.6).…”

“…(a) ∆WELM /W ped versus P inped /P ped for ν* ped = 0.06 (A-D) and (b) ∆WELM /W ped versus ν* ped for P inped /P ped = 0.66 (C). Results in previous study [14] are shown by open symbols A'. In (b), shaded region denotes experimental data [1,2].…”

“…The collisionality dependence caused by the parallel transport was also pointed out by the analytical model [16]. In the previous simulation, however, the ELM energy loss was less than 10 % of the pedestal energy because the mode structure was localized in a pedestal region with a steep pressure gradient [14].…”

The 2008 Public Release of the International Multi-tokamak Confinement Profile Database

“…The ranges of parameters covered in the PR08 discharges from JT-60U are 3.1m ≤ R ≤ 3.4m, 0.74m ≤ a ≤ 0.87m, 1.7T ≤ B t ≤ 4.3T, 0.53MA ≤ I p ≤ 1.8MA, 1.4 ≤ κ ≤ 1.77 and 0.05 ≤ δ ≤ 0.37, while the heating power is in the range 2.7MW ≤ P aux ≤ 25.5MW. All JT-60U discharges were analysed using the 1.5-dimensional transport code TOPICS (TOkamak Prediction and Interpretation Code System) [80,81], which reconstructed MHD equilibria using constraints from a motional Stark effect (MSE) diagnostic [82]. Heating and current drive from neutral beam injection and from electron cyclotron waves were respectively calculated using the OFMC (Orbit Following Monte Carlo) [83] and EC-Hamamatsu [84] codes.…”

Integrated Modeling of Whole Tokamak Plasma

“…In order to study core and edge/pedestal regions, the integrated code TOPICS-IB [5] has been developed on the basis of the 1.5 dimensional (1.5 D) transport code TOP-ICS [6] extended to the integrated simulations for burning plasma. Plasma rotation is another important factor affecting the plasma confinement, the ITB/ETB formation and the RWM suppresstion, and its modeling requires the momentum transport, the formation of radial electric field, whose shear can suppress the turbulence, collisional and j × B torques.…”