Evaluation of a laser speckle interferometry-based diagnostic system for wall surface variation in tokamak device

The realization of high-parameter, long-pulse operation of a tokamak inevitably faces a number of safety and operational constraints, which need to be achieved through comprehensive in-situ monitoring and control of the wall materials. Laser speckle interferometry (LSI) has been proposed to diagnose changes in the surface topography of wall materials. An LSI-based experimental system has been established and a quantitative evaluation process has made for it. The accuracy, range, and uncertainty of measurement are determined by measuring the topography change resulting from laser ablation and pulsed laser deposition. The calculation of measurement uncertainty considers various sources of error such as measurement noise, residual flatness, measurement errors, and measurement repeatability. This evaluation provides an overview of the measurement performance and reliability of the experimental system and helps to clarify the advantages and limitations of LSI for wall surfaces diagnosis. The evaluation can also serve as a useful reference for optimizing the LSI-based measurement system for better adaption to the EAST diagnostic conditions.