Plasma diagnostics at Aditya Tokomak by two views visible light tomography

Plasma imaging has always been a requirement for development of correlations between theoretical and engineering advancements in tokomak reactors. Technological constraints do not allow putting sufficient imaging instruments. This visible tomography exercise is a part of a project for establishing an auxiliary imaging method that would assist other surrounding imaging facilities at Institute of Plasma Research (IPR) India. Space constraints around Aditya Tokomak allow only two orthogonal ports. Data measurement is performed using two arrays of 64 detectors that are sensitive to optical spectrum. The two view arrangement is a worst case scenario (as far as number of projections is concerned) but it is not implausible. An algorithm is developed for such limited detector and limited-view tomography cases. Spatial filtered entropy maximization technique is hybridized with adaptive discretization grids to find the best possible solution. Reconstruction using synthetic projection data, similar to the real measurement geometry, shows that significant reduction in r.m.s. error is obtained. Real time plasma images/profiles are reconstructed using multiple shots of thin hot plasma from Aditya Tokomak. These profiles help to understand the real time plasma-wall interaction at different stages of plasma generation due to edge plasma turbulence. It also helps to control the generation of plasma. (author)