Preliminary Study On The Laser Speckle Interferometry In Tokamak-like White Light And Vibration Environment

Nuclear fusion is the most possible way to solve the problem of human energy.Tokamak is the most likely device to achieve controlled nuclear fusion.During the operation of Tokamak,the plasma facing components(PFCs)will be bombarded by plasma high-energy particle flow and heat flux from the core.This is called as plasma wall interaction(PWI).PWI will lead the erosion and co-deposition on the surface of the PFCs.This changes the surface morphology of the PFCs.In the high parameter and long pulse operation of Tokamak,the erosion and codeposition will become a serious problem,and even affect the safety operation of fusion device.Therefore,it is much desired to realize the real-time monitoring of the surface morphology of the PFCs.Laser speckle interferometry(LSI)is considered to be the most possible approach to realize real-time and non-contact measurement on the surface morphology of PFCs.In order to extract the phase information contained in the interference intensity in the LSI,we introduce the time phase shifting approach in the measurement process.Due to the influence of the background light from Tokamak discharge and the vibrational interference from the tokamak device,the accuracy of the measurement by LSI will be reduced and even failure.In this study,the influence of the background light and vibrational interference on the speckle morphology measurement has been investigated in the laboratory.The specific research contents are as follows:(1)In the experiment,laser ablation and pulsed laser deposition approaches are used to simulate the erosion and deposition on the surface of PFCs in Tokamak.The continuous white light emitted by gas discharge xenon lamp is used to simulate the background light in Tokamak discharge.The morphology changes due to the ablation and deposition on the different samples under the different white light environments are measured by using Michelson-based speckle interferometry system.The results from speckle interferometry are compared with those of White light interferometer and profilometer to analysis the influence of background white light interference on speckle interferometry.(2)Condersing the practical LSI measurement distance in Tokamak,the far-field laser speckle interferometry system has been built.The sample is fixed on the platform without vibration isolation,and the vibration environment of the fusion device is simulated by the vibration environment of the laboratory(mainly from the mechanical pump).At the same time,different phase extraction algorithms are used to extract the phase of the interferogram,and the reconstruction results are compared those from the convenient analysis,so as to investigate the anti-vibration ability of the different phase extraction algorithms.(3)In the far-field LSI experiments in vibration environment,the different CCD exposure time is set to record the interference fringes of the mirror-sample,and the influence of the different sampling time on the fringes contrast is investigated and the theoretical analysis is carried out.