Development of Laser Diagnostic Techniques for Clarification of Particle Behavior in Divertor Region

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Macroscopic behavior in divertor region, such as the position of the ionization front and the distribution of the radiation intensity has to be understood by correlating these with plasma parameters there, such as electron temperature and density, atomic hydrogen density, and impurity density. In this study, we have performed to develop methods to measure the plasma parameters by fully exploiting the potensial of the laser-aided plasma diagnostics. These are Thomson scattering, two photon excited LIF (laser induced fluorescence), and Rayleigh and Raman scattering. The following results have been obtained.(1) Thomson scatteringWe have considered about LIDAR (light detection and ranging) Thomson scattering for divertors, and obtained that the necessary laser, having energy of 1 J and pulse width of 100-300 ps, is realizable using pulse compression technique. Also, a collaboration has been performed with JET divertor LIDAR and a preliminary result was obtained. In addition, lower detectio … More n limit of Thomson scattering has been studies using existing discharge plasmas. As a result, we obtained the detection limit of 1*10^<16>m^<-3>.(2) Two-photo excited LIFThe technique of the two photon excited LIF,applicable for divertor plasmas, has been studied experimentally and theoretically. In particular, we have established the nethod of yielding atomic hydrogen temperature from the deconvolved Doppler spectral profiles.(3) Rayleigh and Raman scatteringWe have demonstrated, for the first time, that Rayleigh and Raman scattering is applicable to measurements of atomic and molecular densities in actual plasmas. In particular, the former has yielded signals from densities of 10^<19>m^<-3>, while the latter has yielded preliminary results and analyzes are underway.We believe these achievements are useful in understanding particle behavior in divertor region, and in correlating these with macroscopic behavior of divertor plasmas, such as ionization front and radiation intensity distributions. Less