On benchmarking of simulations of particle transport in ITER

Abstract

We report results of benchmarking of core particle transport simulations by a collection of codes widely used in transport modelling of tokamak plasmas. Our analysis includes formulation of transport equations, difference between electron and ion solvers, comparison of modules of the 2 pellet and edge gas fuelling on the ITER baseline scenario. During the first phase of benchmarking we address the particle transport effects in the stationary phase. Firstly, simulations are performed with identical sources, sinks, transport coefficients, and boundary conditions prescribed in the flattop H-mode phase. The transformation of ion particle transport equations is introduced so to directly compare their results to electron transport solvers. Secondly, the pellet fuelling models are benchmarked in various conditions to evaluate the dependency of the pellet deposition on the pellet volume, injection side, pedestal and separatrix parameters. Thirdly, edge gas fuelling is benchmarked to assess sensitivities of source profile predictions to uncertainties in plasma conditions and detailed model assumptions. At the second phase, we address particle transport effects in the time-evolving plasma including the current ramp-up to the ramp-down phase. The ion and the electron solvers are benchmarked together. Differences between the simulation results of the solvers are investigated in terms of equilibrium, grid resolution, radial coordinate, radial grid distribution, and plasma volume evolution term. We found that the selection of the radial coordinate can yield prominent differences between the solvers mainly due to differences in the edge grid distribution. The simulations reveal that electron and ion solvers predict noticeably different density peaking for the same diffusion and pinch velocity while with the peaked profile of helium, expected in fusion reactors. The fuelling benchmarking shows that gas puffing is not efficient for core fuelling in H-modes and density control should be done by the high field side pellet injection in contrast to present machines. mode in the current flattop phase depends sensitively on the particle balance of the mixed D-T fuels, He and impurities. In ITER, the neutral beam injection (NBI) does not play a noticeable role neither in the global particle balance [7], nor for the central fuelling. Moreover, the SOLPS modelling [7] predicts dramatic reduction of the gas penetrated from the edge, making the pellet injection the main tool for the density control in the H-mode plasmas, though the gas penetrated from the edge still can play the dominant role for the L-mode operation. Features like the recycling and penetration of He and the fuel into the core plasma are central to understanding the dilution and tritium burnup. The SOL/divertor plasma and its interactions with plasma facing components will set the boundary conditions for the core transport. Eventually, the particle transport alters the heat and the momentum transport so all these non-linear connections need to be understood simultaneously t...

First principles and integrated modelling achievements towards trustful fusion power predictions for JET and ITER

“…In the case of CRONOS, the impurity profiles are homothetic to the electron density profile whereas for JINTRAC the transport is self-consistent calculated and the edge values adjusted in order to fulfil the constraints. In general, both codes agree on particle transport as it has been shown in dedicated benchmarks [11].…”

Ion heating by nonlinear Landau damping of high-n toroidal Alfvén eigenmodes in ITER

“…In the reference case simulation, P fus 503 MW and Q 10.1 are achieved with T e,i (0) ∼ 20 keV. The 0D parameters and plasma profiles obtained in this study show a similar level to the other ITER baseline scenario simulations [43,45,46].…”

“…The electron density profile is prescribed as shown in figure 5(b), satisfying n e /n GW = 1 where n GW 1.19 × 10 20 m −3 is the Greenwald density in the ITER baseline scenario. The ion species' fraction, f z = n z /n e , is assumed as f DorT : f He : f Be : f Ar = 0.375 : 0.08 : 0.02 : 0.0005, corresponding to the effective charge number, Z eff = 1.55 [43]. Then, we solved the heat transport, current density diffusion, and also the EP transport in the flattop phase until the stationary condition is reached.…”

Experimental studies and simulations of hydrogen pellet ablation in the stellarator TJ-II

“…Indeed, pellet injection has been simulated in several tokamaks using the HPI2 code, such as JET [20,21], MAST [22] or Tore Supra [23], reproducing closely the experimental results, even though the homogenization model used assumes spatially homogeneous plasmoid characteristics and heating, a limitation that is partially removed in more self-consistent 1D models [11,12]. In addition, it has been used for theoretical studies and design proposals for ITER and DEMO [19,[24][25][26][27].…”