Wall Conditioning on TEXTOR

Philipps, V.

doi:10.13182/fst05-a693

Cited by 16 publications

(10 citation statements)

References 36 publications

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“…Potential counter measures required for reliable and safe long pulse operation in W7-X are (a) reduction of the C source by operation with cold, detached divertor [63], (b) optimised wall conditioning techniques to avoid carbon layer formation with high fuel content [64], and (c) ultimately change of the PFC material to e.g. tungsten [65].…”

Section: Discussionmentioning

confidence: 99%

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

et al. 2021

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W7-X completed its plasma operation in hydrogen with island divertor and inertially cooled test divertor unit (TDU) made of graphite. A substantial set of plasma-facing components (PFCs), including in particular marker target elements, were extracted from the W7-X vessel and analysed post-mortem. The analysis provided key information about underlying plasma–surface interactions (PSI) processes, namely erosion, transport, and deposition as well as fuel retention in the graphite components. The net carbon (C) erosion and deposition distribution on the horizontal target (HT) and vertical target (VT) plates were quantified and related to the plasma time in standard divertor configuration with edge transform ι = 5/5, the dominant magnetic configuration of the two operational phases (OP) with TDU. The operation resulted in integrated high net C erosion rate of 2.8 mg s−1 in OP1.2B over 4809 plasma seconds. Boronisations reduced the net erosion on the HT by about a factor 5.4 with respect to OP1.2A owing to the suppression of oxygen (O). In the case of the VT, high peak net C erosion of 11 μm at the strike line was measured during OP1.2B which converts to 2.5 nm s−1 or 1.4 mg s−1 when related to the exposed area of the target plate and the operational time in standard divertor configuration. PSI modelling with ERO2.0 and WallDYN-3D is applied in an interpretative manner and reproduces the net C erosion and deposition pattern at the target plates determined by different post-mortem analysis techniques. This includes also the 13C tracer deposition from the last experiment of OP1.2B with local 13CH4 injection through a magnetic island in one half module. The experimental findings are used to predict the C erosion, transport, and deposition in the next campaigns aiming in long-pulse operation up to 1800 s and utilising the actively cooled carbon-fibre composite (CFC) divertor currently being installed. The CFC divertor has the same geometrical design as the TDU and extrapolation depends mainly on the applied plasma boundary. Extrapolation from campaign averaged information obtained in OP1.2B reveals a net erosion of 7.6 g per 1800 s for a typical W7-X attached divertor plasma in hydrogen.

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Section: Discussionmentioning

confidence: 99%

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

et al. 2021

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“…In the past years mainly the boronization of the walls by a glow discharge operated in a gas mixture of 10% B 2 H 6 and 90% He was used, resulting in the deposition of a thin boron layer on the inner walls, which also covers in particular the carbon tiles; see Ref. 17. VUV spectroscopy serves to monitor the temporal evolution of the impurity content in the plasma following a fresh boronization by analyzing the spectra recorded in discharges operated under standard conditions~ohmic heating, plasma current I p ϭ 400 kA, mean electron density n e ϭ 2 ϫ 10 19 m Ϫ3 , toroidal magnetic field B t ϭ 1.9 T!…”

Section: Impurity Monitoring and Identificationmentioning

confidence: 99%

Vacuum Ultraviolet Spectroscopy at TEXTOR

Biel

2005

Fusion Science and Technology

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“…Detailed results from experiments performed at both limiter locks are given in the articles of Brezinsek et al 7 and Philipps. 11…”

Section: Discussionmentioning

confidence: 99%

Limiter Lock Systems at TEXTOR: Flexible Tools for Plasma-Wall Investigation

Schweer

Brezinsek

Esser

et al. 2005

Fusion Science and Technology

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Limiter lock systems on the top and the bottom of the TEXTOR vessel are essential elements for experimental investigations of plasma-wall interaction in a tokamak. The lock systems are designed as user facilities that allow the insertion of wall elements (limiter) and tools for diagnostic (electrical probes, gas injection) without breaking the TEXTOR vacuum. The specially designed holder on top of the central carrier and a powerful vacuum pump system permit the exchange of components within ;1 h. Up to ten electrical signals, four thermocouples, and a gas supply can be connected at the holder interface. Between discharges, the inserted component can be positioned radially and turned with respect to the toroidal magnetic field. Additionally, the central carrier is electrically isolated to apply bias voltages and currents up to 1 kV and 1 kA, respectively. An important feature of the lock system is the good access for optical spectroscopic observation of the inserted components in the vicinity of the edge plasma. The whole spectrum from ultraviolet to infrared is covered by spectrometers and filters combined with cameras. Toroidally and poloidally resolved measurements are obtained from the view on top of the probes while the tangential poloidal view delivers radially and toroidally resolved information. A programmable logic controller (Simatic S5) that is operated inside the TEXTOR bunker and from remote locations outside the concrete wall drives all possible features of the lock system.

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Wall Conditioning on TEXTOR

Cited by 16 publications

References 36 publications

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

Vacuum Ultraviolet Spectroscopy at TEXTOR

Limiter Lock Systems at TEXTOR: Flexible Tools for Plasma-Wall Investigation

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