Principle Proof Diagnostic Study Of Deposition Morphology On The First Wall Of Tokamak By Laser Speckle Interferometry

Tokamak is the most promising magnetic confinement device to achieve thermonuclearfusion and realize the future energy supply.In tokamak device,during steady state operation process,the surface material of the first wall will exposed to high heat load and high particle fluxes,then cause physical and chemical process such as the wall erosion,fuel retention,impurity deposition and co-deposition.Among them,the appearance of the impurity deposition and co-deposition on the first wall to a certain extent will have a great impact on the performance,safety and service life of the tokamak.Moreover,the excessive deposition not only can cause fuel retention and low fuel usage,also will be more prone to secondary impurity sputter,dilute the core plasma eventually lead to disruption.Therefore,in order to maintain the steady state operation of the tokamak and the further investigation of the interaction mechanism between the first wall and plasma during its operation,it is much desired to realize online monitoring of the deposition feature on the first wall.Laser Speckle Interferometry(LSI)is an optical method.LSI can provide non-contact,non-destruction,high precision,high sensitivity and online measurement.LSI is widely used in the measurement of stress,strain and displacement in manufacturing,aerospace and other fields.In addition,LSI is also considered to be the most likely optical diagnosis approach to realize in situ characterization of the first wall surface deposition morphology on the tokamak fusion device.Therefore,in this thesis,a principle proof study of laser speckle interferometry with the temporal phase shifting for the measurement of the first wall surface deposition morphology has been carried out.By simulating the vibration environment of tokamak devices,the effects of the different vibration conditions on the LSI measurement results have been studied,and the vibration resistance capability of the different phase extraction algorithms has been also explored.The specific research contents are as follows:(1)In laboratory,a laser speckle interferometry device based on the structure of Michelson interference was developed,and the four-step temporal phase shifting method was adopted to measure the morphology and thickness of the deposited sample.Laser ablation deposition in a vacuum chamber was used to simulate the deposition phenomenon during the tokamak operation,and the aluminum layer deposited on silicon slices was prepared.Also themeasured results were compared with the profilometry for confirming the feasibility of the laser speckle interference approach applying in tokamak surface morphology monitoring.(2)The device of LSI combined a vibrating bench was built to simulate the vibration condition of the tokamak,and the influence of periodic sinusoidal vibration on the morphology measurement was investigated and analyzed from the perspective of modulation and image quality.(3)The vibration-resistance capability of four-step algorithm,Carre algorithm and Stoilov algorithm were studied by numerical simulation,and the influence of the hardware errors on the results was also evaluated.