JET ITER-like wall—overview and experimental programme

Matthews, G. F.; Beurskens, M.; Brezinsek, S.; Groth, M.; Joffrin, E.; Loving, A.; Kear, M.; Mayoral, M.‐L.; Neu, R.; Prior, P.; Riccardo, V.; Rimini, F.; Rubel, M.; Sips, G.; Villedieu, E.; Vries, Peter de; Watkins, M.L.; Contributors, Efda‐Jet

doi:10.1088/0031-8949/2011/t145/014001

Cited by 309 publications

(226 citation statements)

References 16 publications

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“…The corresponding effective sputtering values averaged concerning the area of the line-of-sight on the limiter are therefore representative of the standard condition case; temperature variation from discharge to discharge is not considered in the analysis of this experiment. Initial results on the Be sputtering yield in connection with ERO modelling from a subset of data have been presented in [8].…”

Section: Fig 5: Timetraces Of Global Plasma Parameters Of Dischargesmentioning

confidence: 99%

Study of physical and chemical assisted physical sputtering of beryllium in the JET ITER-like wall

Brezinsek¹,

Stamp²,

Nishijima³

et al. 2014

Nucl. Fusion

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Abstract:The effective sputtering yield of Be (Y tot Be ) was determined in-situ by emission spectroscopy of low ionising Be as function of the deuteron impact energy (E in = 25 − 175eV ) and Be surface temperature ( ). The later mechanism has been clearly identified by the appearance of BeD A-X emission and quantified in cause of a temperature dependence at which the BeD practically vanishes at highest observed Be limiter temperatures. The recorded T surf dependence, obtained in a series of 34 identical discharges with ratch-up of T surf by plasma impact and inertial cooling after the discharge, revealed that the reduction of BeD is correlated with an increase of D 2 emission. The release mechanism of deuterium in the Be interaction layer is exchanged under otherwise constant recycling flux conditions at the limiter. The reduction of Y chem Be with T surf is also correlated to the reduction of the Be content in the core plasma providing information on the total source strength and Be screening. The chemical assisted physical sputtering, always present at the nominal limiter pre-heating temperature of T surf = 200 • C, is associated with an additional sputtering channel with respect to ordinary physical sputtering which is surface temperature independent. These JET experiments in limiter configuration are used to benchmark the ERO code and verify ITER first wall erosion prediction. The ERO code overestimates the observed Be sputtering in JET by a factor of about 2.5 which can be transferred to ITER predictions and prolong the expected lifetime of first wall elements.

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Section: Fig 5: Timetraces Of Global Plasma Parameters Of Dischargesmentioning

confidence: 99%

Study of physical and chemical assisted physical sputtering of beryllium in the JET ITER-like wall

Brezinsek¹,

Stamp²,

Nishijima³

et al. 2014

Nucl. Fusion

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“…In JET with the JET-ILW all the existing Carbon-fibre Composite (CFC) in direct contact with the plasma have been replaced with bulk beryllium as the predominant main chamber material and with tungsten surfaces in the divertor [2]. The divertor consists of thin (30 microns) W-coated CFC tiles and a single toroidally continuous belt of four-fold bulk tungsten tile at the outer strike point where the heat flux is expected to be the strongest [6].…”

Section: Overview Of the H-mode Development In Jet With The Jet-ilwmentioning

confidence: 99%

First scenario development with the JET new ITER-like wall

Joffrin

Baruzzo²,

Beurskens

et al. 2013

Nucl. Fusion

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In the recent JET experimental campaigns with the new ITER-like wall (JET-ILW), major progress has been achieved in the characterization and operation of the H-mode regime in metallic environments: (i) plasma breakdown has been achieved at the first attempt and X-point L-mode operation recovered in a few days of operation; (ii) stationary and stable type-I ELMy H-modes with βN ∼ 1.4 have been achieved in low and high triangularity ITER-like shape plasmas and are showing that their operational domain at H = 1 is significantly reduced with the JET-ILW mainly because of the need to inject a large amount of gas (above 1022 D s−1) to control core radiation; (iii) in contrast, the hybrid H-mode scenario has reached an H factor of 1.2–1.3 at βN of 3 for 2–3 s; and, (iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Zeff of the order of 1.3–1.4. Strong core radiation peaking is observed in H-mode discharges at a low gas fuelling rate (i.e. below 0.5 × 1022 D s−1) and low ELM frequency (typically less than 10 Hz), even when the tungsten influx from the diverter is constant. High-Z impurity transport from the plasma edge to the core appears to be the dominant factor to explain these observations. This paper reviews the major physics and operational achievements and challenges that an ITER-like wall configuration has to face to produce stable plasma scenarios with maximized performance.

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“…Besides this obvious reconstruction a large amount of details had to be changed/optimized [8] as for example the upper dump plate now consists of bulk Be ribs with beryllium coated Inconel plates between, rather than a continuous sheet of tiles. The anticipated operating limits with the ILW are most fundamentally driven by the relatively low melting point of beryllium (1629 K), the limited robustness of tungsten coatings to slow and fast thermal cycles and the thermal capabilities of the support structures for the bulk tungsten tile [9].…”

Section: Introductionmentioning

confidence: 99%

“…In order to achieve PFC temperature measurements in real time, a comprehensive set of bicolour pyrometers (8) and monochrome video cameras (7) with adjustable filters and thermocouples was installed.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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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.

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JET ITER-like wall—overview and experimental programme

Cited by 309 publications

References 16 publications

Study of physical and chemical assisted physical sputtering of beryllium in the JET ITER-like wall

Study of physical and chemical assisted physical sputtering of beryllium in the JET ITER-like wall

First scenario development with the JET new ITER-like wall

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

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