Overview of physics basis for ITER

Abstract

ITER will be the first magnetic confinement device with burning DT plasma and fusion power of about 0.5 GW. Parameters of ITER plasma have been predicted using methodologies summarized in the ITER Physics Basis (1999 Nucl. Fusion 39 2175). During the past few years, new results have been obtained that substantiate confidence in achieving Q 10 in ITER with inductive H-mode operation. These include achievement of a good H-mode confinement near the Greenwald density at high triangularity of the plasma cross section; improvements in theory-based confinement projections for the core plasma, even though further studies are needed for understanding the transport near the plasma edge; improvement in helium ash removal due to the elastic collisions of He atoms with D/T ions in the divertor predicted by modelling; demonstration of feedback control of neoclassical tearing modes and resultant improvement in the achievable β-values; better understanding of edge localized mode (ELM) physics and development of ELM mitigation techniques; and demonstration of mitigation of plasma disruptions. ITER will have a flexibility to operate also in steady-state and intermediate (hybrid) regimes. The 'advanced tokamak' regimes with weak or negative central magnetic shear and internal transport barriers are considered as potential scenarios for steady-state operation. The paper concentrates on inductively driven plasma performance and discusses requirements for steady-state operation in ITER.

High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade

“…It is a well known fact from ITER confinement database studies [26] that for densities near and beyond the Greenwald value the confinement observed no longer agrees with the scaling and the corresponding H98 values drop significantly below unity. Pellet fuelling experiments performed at JET and AUG showed that in ITER relevant scenarios a density regime beyond values accessible with gas puffing can be accessed but there is no further improvement in the energy confinement [27].…”

Low-frequency linear-mode regimes in the tokamak scrape-off layer

“…[24][25][26][27][28][29][30][31][32]. Both DW and BM instabilities can exist in this range of R=L n and both resistive and inertial effects are important, and therefore we expect the behaviour of the SOL to change remarkably in these wide intervals of parameters.…”

“…The relative importance of each mode, however, is still unclear, and non-linear simulations of edge and SOL turbulent dynamics have addressed both instabilities. The SOL region, in particular, is characterized by a wide range of density gradients and resistivities, [24][25][26][27][28][29][30][31][32] allowing the interplay between E Â B convection and curvature effects to change considerably, depending on the plasma scenario.…”

Flux-surface shaping effects on tokamak edge turbulence and flows

“…The design criteria of the ITER plasma shape with κ = 1.7 and δ = 0.33 (at 95% flux surface) are based on a conservative regime that is well established in present experiments [14]. More extreme variations of flux surface shaping were investigated with the experiment TCV (Tokamakà Configuration Variable) which is able to achieve configurations up to κ = 3 and δ = ±0.5 [15].…”

“…Criteria for design of new magnetized plasma experiments for fusion research like ITER are primarily based on empirical scaling laws for the energy confinement time [14]. First-principle based transport models still require reference to experimental scalings, and are validated mainly only for core plasmas excepting the pedestal region [5].…”