Tomographic reconstruction of emissive profile in the divertor region for the visible light imaging diagnostic on Experimental Advanced Superconducting Tokamak

Abstract

• The emissive profile in the divertor region for the visible light imaging diagnostic on EAST is reconstructed clearly. • The reconstruction algorithm is implemented based on the actual three dimensional model of the first wall of EAST. • Ray tracing method based on the actual parameters is applied to calculate the imaging weight matrix. • Philips-Tikhonov regularization with second-order correction is introduced to enhance the reconstruction quality. A tomographic reconstruction method is developed for the visible light imaging diagnostic system of Experimental Advanced Superconducting Tokamak (EAST) to provide the emissive profile on the poloidal cross section of the divertor region. Weight matrix is calculated by a ray tracing method according to the optical path of the visible light imaging diagnostic system in the delicate three-dimensional grid model of EAST first wall to avoid the influence of complex structures of the divertor region. The Philips-Tikhonov regularization algorithm with second-order correction is adopted to calculate the emissive profile. The phantom tests are performed and the effectiveness of the method is confirmed with signal to noise ratio ( SNR ) at 50. The method is applied to the experimental images detected by the visible light imaging diagnostic and clear peaks are identified in the reconstructed emission profiles, which is in consistent with the radiation belts observed in the experimental images.