Analysis of dual laser Thomson scattering signals on W7-X

A dual laser Thomson scattering has been developed at W7-X: a unique system employing, in combination with a 1064 nm laser, a 1319 nm Nd:YAG laser. Dual-laser Thomson scattering (DLTS) is an advanced diagnostic technique in which two laser pulses of different wavelengths are sent to the plasma with a very short time delay and the two scattered signals are separately and independently measured with the same set of polychromators. For the first time during OP2.1, a dual laser Thomson scattering system was operated stably during the entire experimental campaign. In this work, the dual-wavelength signals recorded in several W7-X discharges are analyzed with different methods and the resulting electron temperature profiles and the experimental errors are discussed, with the aim of identifying the capabilities of this technique.