@article{2d57fceea2b248fea6a5b7a393698b1d,
title = "First operation with the JET International Thermonuclear Experimental Reactor-like wall",
abstract = "To consolidate International Thermonuclear Experimental Reactor (ITER) design choices and prepare for its operation, Joint European Torus (JET) has implemented ITER's plasma facing materials, namely, Be for 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 (≈ factor 10) has 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 D2/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 30% power threshold reduction, a distinct minimum density, and a pronounced shape dependence. The L-mode density limit was found to be 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 re-established only when using gas puff levels of a few 1021 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 β N ≈ 3, hybrids) have been achieved with W concentrations well below the maximum acceptable level.",
author = "R. Neu and G. Arnoux and M. Beurskens and V. Bobkov and S. Brezinsek and J. Bucalossi and G. Calabro and C. Challis and Coenen, {J. W.} and {De La Luna}, E. and {De Vries}, {P. C.} and R. Dux and L. Frassinetti and C. Giroud and M. Groth and J. Hobirk and E. Joffrin and P. Lang and M. Lehnen and E. Lerche and T. Loarer and P. Lomas and G. Maddison and C. Maggi and G. Matthews and S. Marsen and Mayoral, {M. L.} and A. Meigs and Ph Mertens and I. Nunes and V. Philipps and T. P{\"u}tterich and F. Rimini and M. Sertoli and B. Sieglin and Sips, {A. C.C.} and {Van Eester}, D. and {Van Rooij}, G.",
note = "Funding Information: The authors want to thank the colleagues from JET-EFDA for providing their latest results. This work was supported by EURATOM and carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. FIG. 1. View into the JET torus with its new ITER-like wall. The main wall tiles are bulk-Be or Be coated Inconel and W-coated CFC tiles (NBI shine through areas and restraint rings). The divertor is composed of bulk W tiles for the horizontal target and W-coated CFC tiles for the rest. FIG. 2. Reduction of carbon influx and Z eff after the transition from carbon PFCs to Be and W PFCs. FIG. 3. Behaviour of W content and bulk radiation in the L-Mode discharge 81 856 ( B t = 2.55 T , I p = 2.5 MA ). FIG. 4. Radiated energy during the current quench of (un-)mitigated disruption in JET-C and JET-ILW versus the available thermal and magnetic energy (the energy coupled back into the toroidal conductors is subtracted). FIG. 5. Stable H-mode discharge (#82122) in JET-ILW with I p = 2.0 MA , B t = 2.1 T . 66 FIG. 6. Confinement factor H 98 ( y , 2 ) in I p = 2.5 MA , B t = 2.7 T low-δ (circles) and high-δ discharges versus the gas puffing rate in JET-C (black) and JET-ILW (red, filled). FIG. 7. Evolution of W-accumulation in a I p = 2.0 MA , B t = 2.1 T H-Mode discharge (#81913). FIG. 8. Normalized confinement versus N 2 -seeding rate: (a) compared with the H98(y,2) scaling and (b) with the density dependence removed from the H98 scaling. ",
year = "2013",
month = may,
doi = "10.1063/1.4804411",
language = "English",
volume = "20",
journal = "Physics of Plasmas",
issn = "1070-664X",
number = "5",
}