Towards a new image processing system at Wendelstein 7-X: From spatial calibration to characterization of thermal events

Pisano, F.; Cannas, B.; Jakubowski, M.; Niemann, H.; Sitjes, A. Puig; Wurden, G. A.; Team, W X

doi:10.1063/1.5045560

Cited by 17 publications

(18 citation statements)

References 12 publications

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“…For quantitative analysis and comparison, the thermal images from different modules have been restored from the optical distortions caused by the fish-eye lenses used [12], and have been projected onto an identical 2D plane [9]. Heat fluxes have been calculated using the THEODOR code [28] which solves the 2D heat diffusion equation with an explicit method.…”

Section: Observation Of the Overloaded Baffle Tilesmentioning

confidence: 99%

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

et al. 2020

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The operational regimes in the first divertor campaign of W7-X were limited by unexpectedly high heat loads on certain baffle tiles. In the high-mirror configuration, a permanent hotspot on the baffle plate was detected by the thermographic system, which was further confirmed during the post-campaign inspections of the plasmafacing components. The maximum heat load on three baffle tiles reached about 4.5 MW m −2 , which was almost an order of magnitude above its designed value of 0.5 MW m −2 . The paper presents a detailed analysis to understand how the baffle plate, which is originally designed to screen the recycling neutrals and is therefore hidden from the hot plasma, can receive such a high heat load -a level that is expected for target plates. Three main causes have been identified: 1) the three baffle tiles are radially only about 5 mm away from a main heat channel towards a target, which is much shorter than the radial power decay length of several centimeters derived from the thermographic measurements in this region; 2) the three baffle tiles are intersected with field-lines of about 30 m length, which are long enough to collect considerable amount of heat via cross-field transport; 3) the baffle tiles have locally large grazing angles. In addition, the analysis method shown in this paper is of general use to estimate the heat flows in shadow areas of targets and thus to evaluate heat loads on the potentially critical components occurring in these areas, especially required for the design of complex 3D divertors like the one in W7-X.

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Section: Observation Of the Overloaded Baffle Tilesmentioning

confidence: 99%

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

et al. 2020

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“…The synthetic camera model is build on the so-called scene model. For each infrared camera, a pinhole camera model has been created through spatial calibration [17] by taking into account the lens distortion of the camera. By using the camera model and a simplified CAD (Computer Aided Design) model of the observed PFCs, the projection and distortion model of the camera is reconstructed and thus the so-called scene model [18] is created.…”

Section: Scene Model and Synthetic Ir Modelmentioning

confidence: 99%

Validating fast-ion wall-load IR analysis-methods against W7-X NBI empty-torus experiment

et al. 2019

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A : The first neutral beam injection (NBI) experiments in Wendelstein 7-X (W7-X) stellarator were conducted in the summer of 2018. The NBI system is used to heat the magnetically confined plasma by neutralising an accelerated hydrogen ion beam and directing it into the plasma, where the resulting energetic ions release their energy to heat the plasma. The modelling of the NBI fast ion experiments has commenced, including estimation of the shine-through and the orbit-losses. The stellarator has a wide-angle infra red (IR) imaging system to monitor the machine plasma facing component surface temperatures. This work validates the NBI model "Beamlet Based NBI (BBNBI)" and the newly written synthetic IR camera model. The validation is accomplished by comparing the measured and the synthetic IR camera measurements of an experiment where the NBI was injected into the vacuum vessel without a plasma. A good qualitative and quantitative match was found. This agreement is further supported by spectroscopic and calibration measurements of the NBI and and IR camera systems. K: Algorithms, software, data-reduction methods and detectors physics-performance: Simulation methods and programs; Instrumentation and methods for plasma research: Plasma diagnostics -charged-particle spectroscopy; Instrumentation and methods for plasma research: Plasma diagnostics -interferometry, spectroscopy and imaging 1Corresponding author. 2Current affiliation:

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“…The first exemplary use case, utilising images in nuclear fusion, covers algorithms for detecting and tracking thermal events occurring throughout a plasma discharge (see Figure 1). In the Wendelstein 7-X (W7-X), the algorithms identify events such as hotspots, leading edges, strike-lines, surface layers that exceed the operational limits of the stellarator [6][7][8][9][10]. Based on the detected thermal events, the risk is estimated, and if it exceeds the threshold, the interlock system is triggered [2].…”

Section: Image Plasma Diagnosticsmentioning

confidence: 99%

“…The measured temperature is higher due to the lower thermal connection to the component surface. As a consequence, a false hotspot alarm might be triggered [9,10]. The detection scheme is based on the idea of a normalised derivative of the temperature evolution proposed by [14].…”

Section: Surface Layers Detectionmentioning

confidence: 99%

Implementation of Thermal Event Image Processing Algorithms on NVIDIA Tegra Jetson TX2 Embedded System-on-a-Chip

2021

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Advances in Infrared (IR) cameras, as well as hardware computational capabilities, contributed towards qualifying vision systems as reliable plasma diagnostics for nuclear fusion experiments. Robust autonomous machine protection and plasma control during operation require real-time processing that might be facilitated by Graphics Processing Units (GPUs). One of the current aims of image plasma diagnostics involves thermal events detection and analysis with thermal imaging. The paper investigates the suitability of the NVIDIA Jetson TX2 Tegra-based embedded platform for real-time thermal events detection. Development of real-time processing algorithms on an embedded System-on-a-Chip (SoC) requires additional effort due to the constrained resources, yet low-power consumption enables embedded GPUs to be applied in MicroTCA.4 computing architecture that is prevalent in nuclear fusion projects. For this purpose, the authors have proposed, developed and optimised GPU-accelerated algorithms with the use of available software tools for NVIDIA Tegra systems. Furthermore, the implemented algorithms are evaluated and benchmarked on Wendelstein 7-X (W7-X) stellarator experimental data against the corresponding alternative Central Processing Unit (CPU) implementations. Considerable improvement is observed for the accelerated algorithms that enable real-time detection on the embedded SoC platform, yet some encountered limitations when developing parallel image processing routines are described and signified.

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Towards a new image processing system at Wendelstein 7-X: From spatial calibration to characterization of thermal events

Cited by 17 publications

References 12 publications

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

Validating fast-ion wall-load IR analysis-methods against W7-X NBI empty-torus experiment

Implementation of Thermal Event Image Processing Algorithms on NVIDIA Tegra Jetson TX2 Embedded System-on-a-Chip

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