Plasma operation with an all metal first-wall: Comparison of an ITER-like wall with a carbon wall in JET

Transient impurity events in JET with the new ITER-like wall

“…Since the horizontal part of the divertor is a deposition zone for material coming from the main chamber, dust which accumulates in this region could partly be the cause of the occurrence of TIEs. On the other hand, these results are biased by the low externally injected heating power and energy in this configuration, never exceeding ∼ 5 M W and ∼ 0.05 GJ respectively, versus ∼ 25 M W and ∼ 12 GJ delivered in configuration [3,5]. More study is therefore required to better understand these issues.…”

“…Configuration with [inner, outer] strike points on tiles [3,5] has been the most commonly used with the ILW, followed by [4,6], [1,5], [3,7], [3,6] and [4,5] used for respectively 25%, 17%, 15%, 7%, 4% of the operation time spent in configuration [3,5]. Since most high power scenarios were performed in configuration [3,5], its ∼ 30% higher probability with respect to [4,6] is most probably due the power dependence of TIEs. Due to the fact that the normalization has been performed over total plasma-time in each specific configuration, the TIE-probability shown in these plots will increase with the fraction of total time spent at higher heating powers.…”

“…This contribution reports on the study of the occurrence of such transient impurity events (TIEs, also called UFOs) in JET from the installation of the new ITER-Like wall [5]. Such events are visible as sharp increases in the total radiated power similar to what caused by laser ablation experiments.…”

Structure Materials in Fusion Reactors: Issues Related to Tritium, Radioactivity and Radiation-Induced Effects

“…1 show in-vessel components and distribution of wall materials (a) and a section of the bulk tungsten divertor (b). Scientific objectives of the ILW project and challenges in the design and construction of components have been presented by Matthews [9,10] and Mertens [11], while plasma-wall interactions in a full metal machine have been reviewed by Matthews in [12]. The list of candidate structural materials for the blanket comprises mainly steel (e.g.…”

Tungsten coatings under high thermal loads in JET and Magnum-PSI

“…They have been performed with the aim of anticipating the behavior of W coatings in JET to provide a basis for defining allowable operating limits for the coatings. Local coating failures may be responsible for generation of W particles leading to transient radiation events [6] and if sufficient areas were affected could also lead to a rise in carbon levels which would impact fuel retention and plasma behavior [7]. During the JET ILW campaigns the inner strike point was always operated on the tungsten coatings but the outer strike point was mostly positioned on the bulk tungsten tile.…”