Combined Thomson Scattering and Laser-Induced Fluorescence for Studying Divertor and X-point Plasmas in Tokamak with Reactor Technologies

Combined Thomson scattering (TS) and laser-induced fluorescence (LIF) diagnostics are being developed. The Thomson scattering and laser-induced fluorescence are laser diagnostics, with joint both probing and c-ollecting optical systems, which are the most complex and expensive parts of the diagnostic systems of large tokamaks, can be combined. Thomson scattering by free electrons is the use-proven diagnostic method for measuring profiles of important parameters of the plasma electron component (electron tempera-ture T e and electron density n e ), which requires a minimum of model assumptions. Almost all existing tokamaks are equipped with one or more TS systems, and by now, considerable experience has been accumulated in practical methods for implementation of these systems. The use of laser-induced fluorescence for measuring parameters of ion and neutral plasma components is less common, also because it requires knowledge of electron parameters to calculate populations of excited levels. The joint diagnostics of the Thomson scattering and laser-induced fluorescence in divertor plasma will be used to simultaneously measure the plasma parameters necessary for fundamental understanding physics of plasma detachment from divertor plates. These parameters are: the local parameters of plasma electrons ( T e , n e ), ion temperature ( T i ) measured from the data on emission of helium ions (HeII), as well as densities of helium atoms ( n a (He)) and hydrogen isotopes ( n a (H,D,T)). The measured parameters make it possible to calculate the following characteristics: (i) the ionization and recombination rates (using the data on T e , n e , T i , and n a (H, D, T)); (ii) the friction force of the plasma flow due to collisions with neutral particles (using the data on T i , n i (assuming n i = n e ), and n a (H, D, T)); and (iii) the pressure of the oncoming plasma flow (using the data on T e , n e , T i , and n i ). The article discusses advantages of combining laser diagnostics and ways of further development of the joint diagnostcs, based on the experience of creating similar diagnostics for domestic tokamaks and the similar diagnostics developed for ITER.