Tungsten as material for plasma-facing components in fusion devices
TL;DR: In this paper, the use of tungsten (W) as material for plasma-facing components (PFM) in fusion devices is reviewed with respect to its plasma and material compatibility under burning plasmas conditions.
About: This article is published in Journal of Nuclear Materials.The article was published on 2011-08-01. It has received 531 citations till now.
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TL;DR: In this article, the authors consider the risks engendered by the baseline divertor strategy with regard to known W plasma-material interaction issues and briefly present the current status of a possible full-tungsten (W) divertor design.
610 citations
TL;DR: In this article, the authors show that when the gradient in the H-mode transport barrier grows to exceed the MHD stability limit, the ELM instability grows explosively, rapidly transporting energy and particles onto open field lines and material surfaces.
Abstract: Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively, rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heat flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. Encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.
235 citations
TL;DR: In this article, the authors aim at the clarification of the H retention mechanisms with critical review of reported data and presentation of recent results, and present a detailed review of the available data.
Abstract: Although extensive studies on hydrogen (H) retention in tungsten (W) loaded by ion implantation, plasma exposure and gas charging have been done, reported amounts of H retained in W, and their dependences on the incident flux, fluence and temperature are very inconsistent. The present work aims at the clarification of the H retention mechanisms with critical review of reported data and presentation of recent results. H diffusion coefficient for dissolved H in W is large enough to allow for a deep penetration of H into W bulk. Energetic H loading results in H saturation in the subsurface layers. The thickness of the saturated layers could grow under prolonged loading and the H in the layers remain long or hard to remove. Both the growth of the thickness of the saturated layers and the deep penetration of H into the bulk could result in significantly large H retention in W and dissipate the advantage of W as plasma facing wall.
173 citations
TL;DR: In this paper, the ITER-like wall (ILW) was installed in the JET to enable a direct comparison of operation with all carbon plasma facing components (PFCs) to an all metal beryllium/tungsten first-wall under identical conditions.
146 citations
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References
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TL;DR: In this paper, different aspects of the PWI are assessed in their importance for the initial wall materials choice: CFC for the strike point tiles, W in the divertor and baffle and Be on the first wall.
708 citations
TL;DR: In this paper, the authors used mass spectroscopic and ultrahigh vacuum techniques to investigate the solubility and diffusion of hydrogen in tungsten with high temperatures between 1100 and 2400 K. The authors derived the diffusion constants, D = 4.1×10−3×exp (−9000/RT) cm2/sec.
Abstract: Using mass spectroscopic and ultrahigh vacuum techniques, solution and diffusion of hydrogen in tungsten was investigated for pressures between 600 and 10−8 Torr and temperatures between 1100 and 2400 K. Solubility and diffusion constants are derived from degassing rates of a solid cylinder which was pre-loaded with hydrogen at ≈600 Torr. The solubility constant, S=2.9×10−1×exp (−24000/RT) Torr liter/cm3Torr1/2, and the diffusion constant, D=4.1×10−3×exp (−9000/RT) cm2/sec, are obtained, which in conjunction with literature values for the permeation constant P are consistent with the equation P=SD. Comparison to theory indicates that the solubility and diffusion constants are characteristic of interstitially dissolved hydrogen. Expressions are derived for the concentration of interstitial hydrogen as a function of pressure and temperature. Semiquantitative values for the total hydrogen concentration at low pressures are derived from H2 pressure changes which result when a sample is flashed between selecte...
455 citations
TL;DR: In this article, material properties up to high temperatures are presented for lanthanated and W-Re alloys, and the impact on fusion application is discussed Recently developed coatings of chemical vapor deposited tungsten (CVD-W) on copper substrates have proven to be resistant to repeated thermal and shock loading.
291 citations
TL;DR: In this paper, the 3D Monte Carlo code ERO-TEXTOR, based originally on the ERO code, has been developed to simulate the wall interaction and transport processes in the vicinity of a surface positioned in the boundary layer of TEXTOR.
Abstract: The interaction of plasma with the walls has been one of the critical issues in the development of fusion energy research. On the one hand, plasma induced erosion can seriously limit the lifetime of the wall components, while, on the other hand, eroded particles can be transported into the core plasma where they lead to dilution of the fusion plasma and to energy losses due to radiation. Low-Z wall materials induce only small radiation losses in the plasma core but suffer from large physical sputtering rates. Carbon based materials in addition suffer from chemically induced erosion. High-Z wall materials show significantly smaller erosion but lead to large radiation losses. One of the main goals of present plasma-wall studies is to find a special choice of wall materials for steady state plasma scenarios that will provide an optimum with respect to fuel dilution, radiation losses, wall lifetime and fuel inventory in the walls. To obtain a better understanding of the processes and to estimate the plasma-wall interaction behaviour in future fusion devices the 3-D Monte Carlo code ERO-TEXTOR, based originally on the ERO code, has been developed. It models the plasma-wall interaction and transport processes in the vicinity of a surface positioned in the boundary layer of TEXTOR. The main aim is to simulate the erosion and redeposition behaviour of different wall materials under various plasma conditions and to compare this with experimental results. This contribution describes the main features of the ERO-TEXTOR code and gives some examples of simulation calculations to illustrate the application of the code.
240 citations
TL;DR: In this paper, a review of hydrogen isotope retention and migration in tungsten (W) is presented, where a large scatter of the deuterium (D) retention database is used to clarify the mechanism of hydrogen inventory in W. Several points are reviewed: (i) inventory in pure W, (ii) inventory of W pre-implanted by carbon ions, and (iii) inventory inventory in Tungsten oxide.
232 citations