Ex-situ Measurement Of EAST Wall Topography Based On Phase-Shifting Speckle Interferometry And Adaptability Study In Vibration Environment

Fusion energy is one of the ultimate energy sources for the sustainable development of human beings,and magnetic confinement plasma tokamak fusion device is the most possible means to achieve controllable nuclear fusion.During long pulse and steady-state Tokamak operation,plasma wall interaction(PWI)will occur between the boundary plasma and plasma facing material(PFM),which will lead to many problems,such as wall erosion,fuel retention,impurity generation and so on,and seriously affect the operation parameters and operation safety of Tokamak device.Therefore,it is of great significance to study and monitor the process mechanism of PWI.The topography diagnosis and monitoring of the first wall material is of great significance for understanding the wall etching,impurity and fuel deposition,energy flow and ion flow distribution characteristics of Tokamak,as well as understanding of the PWI mechanism.Therefore,it is much desired to develop a real-time,on-line and in-situ method to diagnose the surface topography of the first wall of Tokamak.Optical interference is one of the topography measurement techniques,which can realize full-field,non-destructive,non-contact measurement,and have the advantages of high measurement accuracy,simple structure,strong versatility,and is widely used in the field of surface topography measurement.In order to meet the practical needs of EAST first wall topographic diagnosis,based on the principle of optical interference,combined with temporal phase-shifting technology,dual-wavelength technology and speckle interferometry technology,this thesis develops speckle interferometry image reconstruction algorithm,and aims to establish and improve Dalian University of Technology’s Phase-Shifting Speckle Interferometrty(DUT-PSSI)topographic diagnosis system to satisfy the requirements of EAST first wall topographic diagnosis.The specific research content is as follows:In the second chapter,we introduced the establishment,upgrading and principle demonstration of the phase-shiftting speckle interferometry topography diagnostic system.The DUT-PSSI topography diagnostic system is based on phase-shifting interferometry,and the measurement range is extended by combining dual-wavelength technique.The reconstruction algorithm of DUT-PSSI topography diagnostic system uses the fixed-step phase-shiftting method to extract phase,and uses the Itoh’s method,the branch-cut method and the qualityguide method to get the unwrapping phase,realizing the data reconstruction from the light intensity information to the phase information and then to the spatial information.The reliability of the reconstruction algorithm is verified through numerical simulation,and the principle demonstration of the measurement system is completed through the testing and reconstruction of one-dimensional inclined plane and two-dimensional Gaussian surface.In the third chapter,the feasibility of applying the DUT-PSSI topography diagnostic system to the first wall topography measurement of Tokamak is investigated.In the laboratory testing,samples of Mo and W which are related to the first wall of EAST were processed by laser ablation and pulsed laser deposition technology,and the erosion and deposition of the first wall were simulated respectively by the laser ablation topography and deposited film stepheight topogaphy.The ablation and deposition samples were measured by the improved measurement system in chapter 2,and the results were in good agreement with those measured by profilomete.Considering the first wall compoments of EAST,such as tungsten tile,molybdenum tile or graphite tile,their surface are optically rough,diffuse relection occurs when laser incident on the surface,which can not form interference fringes in interfence mesurement,resulting in the failure of topography measurement.In order to solve this problem,digital speckle pattern interferometry(ESPI)is used to record the speckle pattern of the object surface before and after deformation or displacement.After digital image processing of the speckle patterns,the deformation or displacement information of the object surface can be obtained.In this chapter,the ablation topography of the real EAST tungsten tile with the optical rough surface is measured by DUT-PSSI topography diagnosis system,and the reconstructed topography is obtained successfully.The feasibility of applying DUT-PSSI system to EAST first wall topographic diagnosis is principlely demonstrated.In the fourth chapter,the current DUT-PSSI topography diagnosis system is investigated,and the deficiencies of the system are discussed according to the technical requirements of EAST first wall topography diagnosis,and the future improvement is clarified.In this chapter,the topography of the ablated craters with different ablation pulses and the thickness of deposited films with different deposition time have been measured using DUT-PSSI topography diagnosis system.The results are compared with those measured by white light interferometer for determining the measurement range and measurement error of DUT-PSSI system.In addition,the measurement uncertainty of the system at different wavelengths is calculated considering several factors such as measurement noise,residual flatness,measurement repeatability and measurement error.Finally,the current advantages and challenges of the DUT-PSSI system are summarized from the aspects of measurement range,measurement accuracy,temporal and spatial resolution,coverage area,etc.The work will provide data support for the application of DUT-PSSI system to EAST first wall topography online diagnosis.In the fifth chapter,the topography diagnosis in EAST-related vibrational environment has been studied.The main technology of phase extraction in DUT-PSSI topography diagnosis system is the fixed step phase-shifting method.This method collects multiple interferograms in temporal series,and fixed phase-shifting is introduced between the adjacent interferograms.The vibration from EAST will introduce uncertainty in phase-shifting,and introduce error in phase calculation,which seriously affects the measurement accuracy.In the laboratory,the vibration environment of EAST is simulated by a displacement generator,and the influence of different vibration modes on the measurement accuracy of DUT-PSSI system is studied in detail.At the same time,the reconstruction algorithm and experimental conditions are optimized from two aspects of improving the phase extraction method and optimizing the exposure time,so as to improve the measurement accuracy of DUT-PSSI system in the vibration environment,and make the DUT-PSSI system better adapt to the on-line topography diagnosis in the EAST practical vibration environment.In the sixth chapter,based on the above investigations,the conclusions and prospects are given.