The choice of the laser wavelength for ITER LIDAR THOMSON SCATTERING SYSTEM for the core plasma is linked to the extended range of plasma temperatures1 to be measured, i.e. 0.5–30keV. The additional requirements1 are: temperature relative error ΔTe/Te=0.1 with spatial resolution of 0.1m, plasma density relative error Δne/ne=0.05 and spatial resolution 0.3m, at a temporal resolution of 10ms.These last parameters determine the laser energy, the pulsewidth and the repetition rate. It has been found2 that a single laser working at a wavelength of 790nm solves the problem of measuring the ITER temperature with a relative error less than or equal to 20%. A Titanium-Sapphire laser (Ti:Al2O3) is the natural candidate for such a source since the fluorescence peak is at 800nm, with a very large tunability range between 700 and 1000nm. Other important characteristics of the material are the large gain cross section, and relatively short fluorescence lifetime, its hardness and good thermal conductivity properties inherent to the sapphire host, and the availability in large size, good quality crystals. High power short pulse Ti:Sapphire lasers can be built. The paper is organized as follows: the required laser figures are summarized, the main Ti:Sapphire(TiS) material parameters are listed in comparison to other laser materials, the scheme of a 10Hz TiS laser is presented, the possibilities of improving the previous scheme to 100Hz source are discussed and a comparison with other proposed schemes4 is cited, finally the conclusions are drawn about the possibility of building these sources with present day technology.
