In order to realize the in-situ diagnosis of the surface morphology of Plasma-Facing materials (PFMs) in advanced superconducting tokamaks, such EAST, Dalian University of Technology has developed the Speckle Interference Experiment Platform (DUT-SIEP). In order to ensure high resolution, DUT-SIEP introduces a vibration-sensitive time phase-shifting technique. The influence of environmental vibration leads to a decrease in the accuracy of surface topography measurement for PFMs. Therefore, it is very important to in-situ characterize the vibrational parameters of tokamak device for vibrational disturbance compensation in PFMs surface topography measurement. To this issue, we propose an approach based on Laser Interferometric Quadrature Phase (LIQP) method for measurement of vibrational parameters of tokamak wall for improving the accuracy of surface topography measurement by compensating the phase error introduced by vibration disturbance. The vibration measurement is performed by obtaining two vibrational interferometric signals with phase difference due to the difference of the distance from two photodiodes to the beam splitter mirror, and correcting them to two signals with orthogonal phase difference by the least squares method. By using the inverse tangent calculation and phase unwrapping of the two orthogonal signals, the displacement of the vibrating target is reconstructed in real time. In order to simulate the actual working conditions of the EAST tokamak device, the amplitude and frequency measurements of different vibrations are carried out under the experimental conditions of a three-meter far field. The experimental results demonstrate the potential application of this method in the in situ measurement vibrational parameters of tokamak devices.
Temporal phase-shifting interferometry technique (TPSI) has high accuracy in surface topography metrology and has been designing to diagnose the surface variation of plasma-facing materials (PFMs) in Tokamak. But the mechanical vibration of the Tokamak device will lead to the decrease of the measurement accuracy or even incorrect result. In order to solve the problem more, it is much desired to study the influence of the vibration on the topographic measurement in the broad parameter scope. Series experiments in the different vibration frequencies, amplitudes, modes and different deformation amounts and detection wavelengths were carried out in this work.
Monitoring the deformation caused by wall erosion and deposition on the Plasma-Facing Components (PFCs) in tokamak has been essential issues for the maintenance of a long duration plasma discharge and safety. As an in situ, real-time and non-destructive optical diagnostic technique, Laser Speckle Interferometry (LSI) based on temporal phase-shifting approach has been considered as the most potential approach for the measurement of erosion and deposition on PFCs. This paper focuses on the measurement of the deposition morphology and thickness based on the temporal phase-shifting laser speckle interferometry. Here the deposition was conducted by Pulse Laser Deposition (PLD) in a vacuum chamber, which is simulated to the deposition process on PFCs. The LSI measurements are compared with those of profilometry and the results show that the temporal phase-shifting laser speckle interferometry is capable of online measuring deposition morphology as well as thickness. The LSI approach has great possibility for the further application on the real-time monitoring impurity and fuel deposition on PFCs in fusion devices.
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