The spectrometer of the high-resolution multiposition Thomson scattering diagnostic for TJ-II

A high-resolution multi-position Thomson scattering system, which combines high accuracy and excellent spatial resolution, is operating on the stellarator TJ-II. Its diagnostic spectrometer is presented here. Its main characteristics, which provide the TJ-II Thomson scattering diagnostic with high spatial and spectral resolution, 2.2 mm and 2.1 nm, respectively, are described in this paper. In particular, the viewing optics has been designed in order to achieve low aberrations and distortions. The detector branch, which acts during a short pulse, ensures correct light intensification and synchronization with the laser beam. These attributes allow one to discriminate small-scale features that appear in density and temperature profiles in TJ-II plasmas, as well as steep gradients in both temperature and density profiles. Examples of results obtained demonstrating the characteristics of this system are presented.