Bidirectional reflectance measurement of tungsten samples to assess reflection model in WEST tokamak

Yaala, M. Ben; Aumeunier, M.-H.; Steiner, Roland; Schönenberger, M.; Martin, Céline; Bohec, M. Le; Talatizi, C.; Marot, L.; Meyer, Ernst

doi:10.1063/5.0046140

Cited by 10 publications

(4 citation statements)

References 19 publications

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“…This may cause a systematic error while interpreting experimental results in terms of the locations of the highest radiation. Together with the BRDF measurements [14], a better refined CAD model, and better Cherab and Raysect libraries, a physically reliable WEST tokamak model should be implemented.…”

Section: Discussionmentioning

confidence: 99%

“…Although the bolometry system is well-designed and operational on the WEST tokamak [13], the synthetic diagnostic code SYNDI [13] currently used to predict bolometry signals is not able to handle non-axysimmetric geometries of PFCs and the tokamak vessel. Moreover, because bidirectional BRDF is still under investigation for the WEST PFCs [14], one can use the Cherab library to adjust optical properties in the model by using a similar approach to that used in [8] and investigating the influence of different materials on the signals.…”

Section: Introductionmentioning

confidence: 99%

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Development of a Set of Synthetic Diagnostics for the Confrontation between 2D Transport Simulations and WEST Tokamak Experimental Data

et al. 2022

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Transport codes are frequently used for describing fusion plasmas with the aim to prepare tokamak operations. Considering novel codes, such as SolEdge3X-HDG, synthetic diagnostics are a common technique used to validate new models and confront them with experimental data. The purpose of this study is to develop a set of synthetic diagnostics, starting from bolometer and visible cameras for the WEST tokamak, in order to compare the code results with the experimental data. This research is done in the framework of Raysect and Cherab Python libraries. This allows us to process various synthetic diagnostics in the same fashion in terms of 3D ray tracing with volume emitters developed specifically for fusion plasmas. We were able to implement the WEST tokamak model and the design of bolometer and visible cameras. Synthetic signals, based on full-discharge WEST plasma simulation, were used for to compare the SolEdge3X-HDG output plasma with experimental data. The study also considers the optical properties of the plasma-facing components (PFCs) and their influence on the performance of diagnostics. The paper shows a unified approach to synthetic diagnostic design, which will be further extended to cover the remaining diagnostics on the WEST tokamak.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Development of a Set of Synthetic Diagnostics for the Confrontation between 2D Transport Simulations and WEST Tokamak Experimental Data

et al. 2022

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“…The Bidirectional Reflectance Distribution Function (BRDF), which describes the photon behaviour on a surface for any incident and viewing direction, is a determinant factor for the fidelity of ray-tracers and the understanding/simulation of the optical measurements. Systematic measurements and experimental characterisation of the BRDF for tungsten samples (before plasma exposure) have been performed in order to establish reliable BRDF models (to be used in the synthetic IR diagnostic) for different surface states (roughness, deposit, etc) [8,9]. The experimental results demonstrate the high specular behaviour of W samples, in particular in the IR range [3-5 µm], fitting roughly with classical models of BRDF implemented in ray tracers (as Gaussian, micro-facet models).…”

Section: Materials Properties Characterisationmentioning

confidence: 99%

Surface temperature measurement from infrared synthetic diagnostic in preparation for ITER operations

Aumeunier,

Juven,

Gerardin

et al. 2024

Nucl. Fusion

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The protection of ITER in-vessel components and the plasma-wall interaction studies will be based on a large network of infrared (IR) cameras covering 70% of the tokamak. The surface temperature measurement from IR images remains challenging due to the presence of metallic targets, with changes in surface thermo-radiative properties (emissivity) and the presence of multiple reflections. The paper provides an overview of major progress to improve the interpretation of IR image and to get more reliable surface temperature from IR synthetic diagnostics. The paper presents the latest development of (1) the forward model to include the modelling of the edge localised modes and a new advanced camera that is better adapted to experimental data (2) the inverse model to retrieve the emissivity of the targets and the surface temperature from a neural network trained exclusively from synthetic IR images. Promising results have been obtained both from simulated test images with an estimated emissivity better than 0.05 and a surface temperature better than 10%, and from WEST experimental images of ITER-like wide-angle to filter reflection patterns.

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“…The observed reflections between the divertors and the wall heat shields are shown in Figure 10. Although the wall heat shields were made of graphite during Operational Phase (OP) 1.2, which has low reflectivity, the reflections might still occur on this PFC, according to the reflection map [6] generated for W7-X with a Monte-Carlo Ray-Tracing model by [39].…”

Section: Reflection Detectionmentioning

confidence: 99%

Evaluation of NVIDIA Xavier NX Platform for Real-Time Image Processing for Plasma Diagnostics

et al. 2022

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Machine protection is a core task of real-time image diagnostics aiming for steady-state operation in nuclear fusion devices. The paper evaluates the applicability of the newest low-power NVIDIA Jetson Xavier NX platform for image plasma diagnostics. This embedded NVIDIA Tegra System-on-a-Chip (SoC) integrates a Graphics Processing Unit (GPU) and Central Processing Unit (CPU) on a single chip. The hardware differences and features compared to the previous NVIDIA Jetson TX2 are signified. Implemented algorithms detect thermal events in real-time, utilising the high parallelism provided by the embedded General-Purpose computing on Graphics Processing Units (GPGPU). The performance and accuracy are evaluated on the experimental data from the Wendelstein 7-X (W7-X) stellarator. Strike-line and reflection events are primarily investigated, yet benchmarks for overload hotspots, surface layers and visualisation algorithms are also included. Their detection might allow for automating real-time risk evaluation incorporated in the divertor protection system in W7-X. For the first time, the paper demonstrates the feasibility of complex real-time image processing in nuclear fusion applications on low-power embedded devices. Moreover, GPU-accelerated reference processing pipelines yielding higher accuracy compared to the literature results are proposed, and remarkable performance improvement resulting from the upgrade to the Xavier NX platform is attained.

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Bidirectional reflectance measurement of tungsten samples to assess reflection model in WEST tokamak

Cited by 10 publications

References 19 publications

Development of a Set of Synthetic Diagnostics for the Confrontation between 2D Transport Simulations and WEST Tokamak Experimental Data

Development of a Set of Synthetic Diagnostics for the Confrontation between 2D Transport Simulations and WEST Tokamak Experimental Data

Surface temperature measurement from infrared synthetic diagnostic in preparation for ITER operations

Evaluation of NVIDIA Xavier NX Platform for Real-Time Image Processing for Plasma Diagnostics

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