First operation with the JET International Thermonuclear Experimental Reactor-like wall

Abstract

AbstrAct.To consolidate ITER design choices and prepare for its operation, JET has implemented ITER's plasma facing materials, namely Be at the main wall and W in the divertor. In addition, protection systems, diagnostics and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs), but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (Section 1factor 10) have led to much lower radiation during the plasma burn-through phase eliminating breakdown failures.Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D 2 /Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a reduced power threshold by 30%, a distinct minimum density and pronounced shape dependence. The L-mode density limit was found up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be only re-established when using gas puff levels of a few 10 21 es −1. On average the confinement is lower with the new PFCs, but nevertheless, H factors up to 1 (H-Mode) and 1.3 (at b N ≈ 3, hybrids) have been achieved withWconcentrationswell below themaximum acceptable level.

The impact of poloidal asymmetries on tungsten transport in the core of JET H-mode plasmas

“…1,2 This, in combination with the recent decision to start ITER operation directly with a W divertor, has strongly motivated studies dedicated to the investigation, the modelling and the prediction of the W behaviour in JET-ILW plasmas in different operational regimes and discharge scenarios. [3][4][5][6] Clear evidence has been produced that in the core of JET-ILW plasmas, W transport is dominated by neoclassical transport.…”

Application of a grid numerical method to calculate state-selective cross sections for electron capture inBe4++H(1s)collisions

“…q+ ions are especially relevant because Be will be used as the armor material of the first wall of the International Thermonuclear Experimental Reactor (ITER) (see [1]) and an ITER-like wall is already under operation in the Joint European Torus (JET) [2,3]. Chemical and physical erosion of the first wall releases beryllium atoms and several molecular species, which eventually lead to the presence of fully stripped beryllium ions in the plasma core.…”

Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus

“…The plasmas were designed to study the movement of eroded plasma facing material within JET's vacuum vessel 1 after the installation of JET's new ITER-like wall, 2 and each had about 6 s of H-mode of which 2-3 s at the end was exceptionally steady. Combining the data from the 2 s period prior to the end of H-mode from each of the 120 pulses provides 240 s of plasma with $10 000 edge-localised plasma instabilities (ELMs).…”