Establishment And Application Of Laser Speckle Interferometry Experimental Platform For EAST First Wall Morphology Diagnostics

Clean and safe nuclear fusion energy is particularly important for solving the energy supply problem in China,and magnetic confinement Tokamak is currently the most promising way to achieve controlled thermonuclear fusion.The realization of magnetic confinement fusion energy mainly faces two bottleneck problems in physics and material research.The first problem is about high parameter steady-state plasma physics and the second problem is related to key materials in Tokamak devices and future fusion reactors.The study of Plasma Wall Interaction(PWI)process and mechanism is helpful to solve above two problems.Studies of PWI process and mechanism as well as PWI effective control are core issues in the achievement of controlled thermonuclear fusion and they are also great significant for the design and construction of China Fusion Engineering Test Reactor(CFETR).Laser speckle interferometry is a kind of real-time measurement technology in non-contact way and it has many advantages,such as high accuracy and wide application.Therefore,it is an important research approach for the dynamic monitoring of tokamak first wall,and it can be used to in-situ measure the surface morphology states of the first wall materials,such as the surface displacement,stress and strain,materials erosion and redeposition,etc.In this thesis,the application of laser speckle interferometry in the dynamic monitoring of tokamak first wall is the research background and the following works have been carried out.In chapter 2,Speckle Interferometry Experiment Platform in Dalian University of Technology(DUT-SIEP)has been established for Tokamak first wall morphology research in laboratory conditions,and DUT-SIEP is composed of three main hardware sub-systems:Laser source system,High-precision piezoelectric ceramic displacement system and High-resolution imaging system.Laser source system includes a tunable dye laser,an OPO laser,a diode laser and a He-Ne laser.These lasers can provide selectively laser wavelength and energy output for satisfying the different requirements of the surface morphology states and the reflectivity of the measured materials.High-precision piezoelectric ceramic displacement system consists of piezoelectric phase shift sensor and high sensitivity drive controller.It has sub-millisecond response time and 0-2 micron high-precision displacement range with 0.1 nanometer effective resolution.High-resolution imaging system can be controlled by the external trigger timing sequence and synchronized with nanosecond pulse laser with 2208[H]3000[V]resolution and high-speed acquisition.In chapter 3,in order to reach the technical specifications of EAST first wall morphology diagnosis,three main hardware sub-systems of DUT-SIEP were all connected with the integrated control terminal.Through the independent development of DUT-SIEP software program working for integrated control and image data acquisition,DUT-SIEP can realize programmed remote control of laser speckle interferometry measurement,with the benefit of the function integration of timing synchronization and high-speed acquisition.DUT-SIEP has become a significant off-line test platform for tokamak first wall morphology diagnosis,and it provides more technical guidance for solving the difficulties of online dynamic monitoring of tokamak first wall.In chapter 4,the surface morphology measurements of laser ablation craters with different laser pulse numbers on tungsten mirror and molybdenum mirror by means of speckle interferometry were carried out based on DUT-SIEP.Laser ablation method was utilized to simulate a microscale morphology changes on the surface of tokamak-like first wall materials.Single-wavelength method and two-wavelength approach of speckle interferometry technique were employed for measuring the surface morphology of these laser ablation craters.The measurement accuracy and the reliability of DUT-SIEP have been verified by the comparison results among laser speckle interferometry and profilometer and confocal microscope.These benchmarked measurements as important principle proof are significant for the future research of online EAST first wall morphology diagnosis.In chapter 5,the study on the morphology diagnosis of a real EAST divertor tiles has been performed on DUT-SIEP and the remote experimental condition of real EAST environment was carefully considered.Through the analysis of measurements and diagnosis for real EAST divertor tiles,two-wavelength speckle interferometry approach is confirmed as the dynamic monitoring scheme for EAST first wall.The feasibility and reliability of DUT-SIEP integrated control terminal and software program have been proved again.The timing synchronization and high-speed acquisition of DUT-SIEP are qualified to the challenge of EAST on-line first wall morphology diagnosis and monitoring.As an off-line test platform,DUT-SIEP provides more preliminary data and valid design reference for the future on-line dynamic monitoring platform on EAST.