Conclusions about the use of tungsten in the divertor of ASDEX Upgrade

Krieger, K.; Maier, H.; Neu, R.

doi:10.1016/s0022-3115(98)00890-3

Cited by 139 publications

(108 citation statements)

References 24 publications

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“…Therefore ASDEX Upgrade has chosen the coating solution. In preparatory experiments using markers [3][4][5][6], the erosion at different positions of the PFCs has been evaluated and the thickness and the technique for coating were chosen accordingly. In 1995 [7], and again from 2000 onward [8] the W coatings were qualified and tested.…”

Section: Rationales For the Use Of W Coatings And Results On Their Pementioning

confidence: 99%

Operational conditions in a W-clad tokamak

Neu

Hopf

Kallenbach

et al. 2007

Journal of Nuclear Materials

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119

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Key word codes: C0600, T1000, P0500, D0500, F0400Experiments with tungsten plasma facing components (PFCs) are performed in the ASDEX Upgrade divertor tokamak and the area covered by W-PFCs has been increased steadily since 1999 reaching 85% for the 2005/2006 campaign. The configurations chosen are W coatings on graphite and CFC. The different locations are subject to different power loads and erosion yields. This is taken into account by selecting different thicknesses in the W-coating manufactured either by physical vapour deposition or vacuum plasma spraying. Power loads in excess of 15 MW/m 2 can be handled in this way. The experiments on ASDEX Upgrade show that plasma operation is feasible with walls and divertor surfaces mostly covered with tungsten, but also reveal critical issues: Fast particles from plasma heating can play a crucial role in W erosion and particle transport must be kept high enough to overcome high impurity content and to prevent central impurity accumulation.

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Section: Rationales For the Use Of W Coatings And Results On Their Pementioning

confidence: 99%

Operational conditions in a W-clad tokamak

Neu

Hopf

Kallenbach

et al. 2007

Journal of Nuclear Materials

Self Cite

119

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“…These higher forces would make the transition from a device designed for C-based PFCs very costly and time consuming and therefore ASDEX Upgrade has chosen the coating solution. In preparatory experiments using markers [4][5][6][7], the erosion at different positions of the PFCs has been evaluated and the thickness and the technique of the coating was chosen accordingly [8,9]. It turned out that thin coatings (d £ 10µm) could be reliably produced on graphite using physical vapour deposition (PVD) techniques.…”

Section: The Road To An All W Devicementioning

confidence: 99%

Final steps to an all tungsten divertor tokamak

Neu

Bobkov

Dux

et al. 2007

Journal of Nuclear Materials

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Currently 85% of the plasma facing components of ASDEX Upgrade are tungsten coated.Carbon influx from W PFCs is still observed but a reduction of the C content is found in plasma discharges and a lower C fraction is measured in deposited layers in agreement with modelling. W sputtering from the low field side guard and ICRF limiters is mainly due to fast particles from NBI as well as from ions accelerated in the rectified sheath during ICRF operation. The increase of the W source area is reflected in increased W concentrations.For medium to high density discharges the techniques developed so far, namely central heating and ELM pace-making, allow keeping the W concentration in the range of 10Boronisation strongly reduces the W influxes and similarly the W content especially during ICRF operation, but this reduction is only temporary and equilibrium is reached already after about 100 discharges.

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“…Fuel retention in ITER is expected to be dominated by erosion of the CFC (carbon fiber composite) target and subsequent co-deposition of tritium in hydrocarbon layers [1]. Retention of fuel in metallic materials is known to be much lower than in hydrocarbon deposits [2], therefore, codeposition of tritium in hydrocarbon layers is likely to dominate the retention of fuel in ITER.…”

Section: Introductionmentioning

confidence: 99%

Sticking coefficient and SIMS of hydrocarbons on fusion relevant plasma-sprayed tungsten surfaces

Schustereder

Rasul

Endstrasser

et al. 2007

Nuclear Instruments and Methods in Physics Research Section B:

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Abstract:In this work we concentrate on the quantification of the sticking coefficient of CD 3 + on fusion relevant plasma-sprayed tungsten (PSW) surfaces in the collision energy range from about 0 up to 100 eV. PSW samples were cut from ASDEX Upgrade tiles and both untreated and electropolished surfaces are investigated. A collision energy, E coll , selected CD 3 + ion beam deposits hydrocarbon layers onto the target surfaces which are ex-situ analysed by Nuclear Reaction Analysis (NRA) via D( 3 He,p) 4 He at 800 kV and 2.5 MeV, respectively. The sticking coefficient, S, for deuterium has been found to be collision energy dependent, decreasing with increasing energy. It is in the order of S~0.4 for PSW and S0.1 for electro polished PSW at E coll = 10 eV. Secondary ion mass spectra of charged particles are recorded after ion-surface collisions with the polished PSW surface for collision energies up to 100 eV. While at very low collision energies below about 10 eV only simple reflection of CD 3 + is observed, at higher collision energies both fragmentation of the projectile and fragmentation of ion-surface reaction products are observed. Concerning the stability of the layers we prove that hydrogen exchange plays a role on the time scale of weeks.

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Conclusions about the use of tungsten in the divertor of ASDEX Upgrade

Cited by 139 publications

References 24 publications

Operational conditions in a W-clad tokamak

Operational conditions in a W-clad tokamak

Final steps to an all tungsten divertor tokamak

Sticking coefficient and SIMS of hydrocarbons on fusion relevant plasma-sprayed tungsten surfaces

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