Interpretation of temperature distribution observed on W-ITER-like PFUs in WEST monitored with a very-high-resolution IR system

Grosjean, A.; Aumeunier, M.-H.; Corre, Y.; Firdaouss, M.; Gaspar, J.; Gerardin, J.; Gunn, J.; Courtois, X.; Dejarnac, R.; Diez, M.; Dubus, L.; Houry, M.; Pocheau, C.; Tsitrone, E.

doi:10.1016/j.fusengdes.2021.112387

Cited by 6 publications

(4 citation statements)

References 30 publications

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“…This toroidal bump is observed on most of the PFU with overexposed leading edges and no shadowing from the upstream PFU (positive misalignment, see table 1) at the maximal loaded location for the PFU #07 and 08 and also close to the minimal loaded area with respect to the ripple modulation for the PFU#17. This pattern makes the IR analysis more complex as this pattern can evolve also during the campaign and with the strike point location [34]. The potential mechanisms leading to such feature, in particular the ion Larmor smoothing effect, have been studied in [34].…”

Section: Emissivity Pattern Of the Sectors Q4b And Q3b Post-c4mentioning

confidence: 99%

“…This pattern makes the IR analysis more complex as this pattern can evolve also during the campaign and with the strike point location [34]. The potential mechanisms leading to such feature, in particular the ion Larmor smoothing effect, have been studied in [34]. Still on the OSP area, the PFUs #14, #18 and #20 exhibit also strong emissivity up to 0.8 (figure 9.d) because of the recessed position of these PFU regarding the previous one (negative value of the misalignment, see table 1).…”

Section: Emissivity Pattern Of the Sectors Q4b And Q3b Post-c4mentioning

confidence: 99%

“…This pattern makes the IR analysis more complex as this pattern can also evolve during the campaign and with the strike point location [34]. The potential mechanisms leading to such features, in particular the ion Larmor smoothing effect, have been studied in [34].…”

Section: Emissivity Pattern Of Sectors Q4b and Q3b Post-c4mentioning

confidence: 99%

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Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Gaspar¹,

Corre²,

Rigollet³

et al. 2022

Nucl. Fusion

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This paper summarizes the emissivity measurements performed on the plasma facing units (PFU) of the WEST lower divertor during the first phase of WEST running with a mix of actively cooled ITER-like PFUs made of bulk tungsten and inertially cooled PFUs made of graphite with a coating of tungsten. In-situ assessment of the emissivity and laboratory measurements after removing the W-coated graphite and ITER-grade PFUs from the WEST device are shown. The measurements exhibit a complex pattern with strong emissivity variation as function of space and time mainly explained with the variation of magnetic equilibrium (strike point location) as well as the plasma performances during the experimental campaigns. The exposed ITER-grade PFU exhibits sharp spatial variation of the emissivity from 0.05 to 0.85 at a monoblock scale (12mm) at the transition of the erosion (strike point location) and deposition (next to the strike point location) areas on the high field side. In the low field side, the emissivity varies from 0.12, at the strike point location, to 0.2 few cm away in the low field side direction. This emissivity range after exposure is much higher than the emissivity variation of unexposed PFU with emissivity from 0.09 to 0.15. In-situ observation performed on the W-coated graphite PFU shows a rapid evolution, typically few pulses, of the emissivity in the inner and outer strike point location. The whole spatial distribution is discussed as well as his variation due to the plasma operation from the start-up of WEST to the removal of the tungsten (W) coated graphite components.

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Section: Emissivity Pattern Of the Sectors Q4b And Q3b Post-c4mentioning

confidence: 99%

Section: Emissivity Pattern Of the Sectors Q4b And Q3b Post-c4mentioning

confidence: 99%

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Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Gaspar¹,

Corre²,

Rigollet³

et al. 2022

Nucl. Fusion

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“…The thermal modelling gives the spatial distribution of the surface temperature (T FEM ) that is used afterward to compute the synthetic temperature (T synth ) as seen by the IR camera as depicted in [20]. To simulate the pixel size, optical blurring and deformation, the numerical radiance profile (calculated from T FEM using Planck equation) is convoluted with the transfer function of the instrument which is modelled by a Gaussian shape with a standard deviation σ=0.175 mm for the VHR system as mentioned in [21]. The parallel heat flux was adjusted to reach the melting point on the leading edge assuming heat flux decay length λ q =10 mm on target (value obtain during C4 experiment with similar heating power) and position of the OSP y 0 =4.2 mm to get the maximum heat flux in the centre of the groove (y qmax =6 mm).…”

Section: Experimental Set-upmentioning

confidence: 99%

Sustained W-melting experiments on actively cooled ITER-like plasma facing unit in WEST

et al. 2021

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The consequences of tungsten (W) melting on divertor lifetime and plasma operation are high priority issues for ITER. Sustained and controlled W-melting experiment has been achieved for the first time in WEST on a poloidal sharp leading edge of an actively cooled ITER-like plasma facing unit (PFU). A series of dedicated high power steady state plasma discharges were performed to reach the melting point of tungsten. The leading edge was exposed to a parallel heat flux of about 100 MW.m−2 for up to 5 s providing a melt phase of about 2 s without noticeable impact of melting on plasma operation (radiated power and tungsten impurity content remained stable at constant input power) and no melt ejection were observed. The surface temperature of the MB was monitored by a high spatial resolution (0.1 mm/pixel) infrared camera viewing the melt zone from the top of the machine. The melting discharge was repeated three times resulting in about 6 s accumulated melting duration leading to material displacement from three similar pools. Cumulated on the overall sustained melting periods, this leads to excavation depth of about 230 μm followed by a re-solidified tungsten bump of 200 μm in the JxB direction.

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Very High spatial Resolution IR thermography diagnostic positioning system upgrade in WEST Tokamak

Dubus

Houry

Pocheau

et al. 2023

Fusion Engineering and Design

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Interpretation of temperature distribution observed on W-ITER-like PFUs in WEST monitored with a very-high-resolution IR system

Cited by 6 publications

References 30 publications

Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Sustained W-melting experiments on actively cooled ITER-like plasma facing unit in WEST

Very High spatial Resolution IR thermography diagnostic positioning system upgrade in WEST Tokamak

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