Techniques Used for Registration and Reconditioning of Infrared Images of the Experimental Advanced Superconducting Toka
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ORIGINAL RESEARCH
Techniques Used for Registration and Reconditioning of Infrared Images of the Experimental Advanced Superconducting Tokamak (EAST) Divertor Zhendong Yang1,2 Bing Tang2
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Yue Wang1 • Chengwen Zhang1 • Pei He1 • Shuangbao Shu3 • Jiayuan Zhang4
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Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The heat flux loaded on the divertor is an important issue in tokamaks. At present, the heat flux on the divertor is calculated from the divertor surface temperature measured by the infrared (IR) camera. However, the movement of the field of view and the geometrical distortion are present in the IR images. Small movements occur with machine shaking during normal discharges, while large ones often arise at disruptions or the rapid variations in the magnetic field. As a result, it is difficult to obtain the real temperature evolution on the specified divertor surface from the IR images. In this paper, the scale invariant feature transform descriptors and K-means clustering have been applied for vibration correction on the IR videos in EAST. The projective transformation is used to correct the geometrical distortion in the IR images. The experimental results show that the proposed methods are efficient in compensating for image translations brought about by vibrations and for perspective distortions in the images, thereby allowing assignment of the IR emission-derived surface temperatures to the correct locations on the divertor surface. Keywords IR image SIFT descriptors K-means clustering Projective transformation
Introduction During the last decade, digital cameras such as IR cameras and visible cameras have been widely used in Tokamak machines such as DIII-D [1], NSTX [2], and ASDEX Upgrade [3]. The first wall temperature measured by IR camera is mainly used to monitor the operation safety of tokamak machines [4] and calculate the heat flux onto the
& Zhendong Yang [email protected] 1
Tongling University, 1335 Cuihu 4th Road, Tongling 244000, Anhui, China
2
Anhui Tongfeng Electronics Co. Ltd, Tongling 244000, China
3
School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, Hefei 230009, China
4
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
tokamak divertor. In order to obtain a wider viewing coverage of vacuum vessel, an optical system for visible and IR imaging has been developed and installed in many fusion machines, such as Tore–Supra [5] and JET [6]. These optical systems can provide large fields of view, and in some cases can provide the same field of view for both IR and visible cameras [6]. Such systems are beneficial for observing and studying plasma-wall interactions. But it also brings technical difficulties in data interpreting from the camera, such as the translation of the field of view and the image distortion. Throughout the image acquisition process, the sources of movements in the camera and the endoscopic diagnostic systems may
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