Measurement of the surface morphology of plasma facing components on the EAST tokamak by a laser speckle interferometry approach

The laser speckle interferometry approach provides the possibility of an in situ optical noncontacted measurement for the surface morphology of plasma facing components(PFCs),and the reconstruction image of the PFC surface morphology is computed by a numerical model based on a phase unwrapping algorithm.A remote speckle interferometry measurement at a distance of three meters for real divertor tiles retired from EAST was carried out in the laboratory to simulate a real detection condition on EAST.The preliminary surface morphology of the divertor tiles was well reproduced by the reconstructed geometric image.The feasibility and reliability of this approach for the real-time measurement of PFCs have been demonstrated.

Diagnosis of the surface morphology of laser-ablated materials using the weightedDCT approach in laser speckle interferometry for application to plasma facing materials

To implement on-line, real-time monitoring for the surface morphology of Plasma-Facing Materials(PFMs) in tokamak, we developed a Laser Speckle Interferometry measurement approach. A laser ablation method was used to simulate the erosion process during Plasma-Wall Interactions in a tokamak. In the present investigation, we evaluated the results of laser ablation morphology changes on the surface of Mo material reconstructed by four different approaches(Flood-fill, Quality-guided, Discrete Cosine Transform(DCT) and Weighted-DCT). The morphology results measured by the weighted-DCT approach are very close to the measurement results from confocal microscopy with an average error rate within 7%. It is verified that the weighted-DCT algorithm has high accuracy and can efficiently reduce the influence of noise pollution coming from laser ablation, which is used as a proxy for erosion from plasma wall interaction. Additionally, the CPU computer time has been shortened. This is of great significance for the real-time monitoring of PFMs’ morphology in the Experimental Advanced Superconducting Tokamak(EAST) in the future.