Validations Of Calibration-Free Measurements Of Electron Temperature Using Double-Pass Thomson Scattering Diagnostics From Theoretical And Experimental Aspects

This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (T-e) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured T-e and intensity of the signals. How accurate the values are depends on the electron temperature (T-e) and scattering angle (theta), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high T-e and a large scattering angle (theta) yield accurate values. Indeed, the errors for scattering angle theta = 135 degrees are approximately half of those for. = 115.. The method of determining the Te in a wide Te range spanning over two orders of magnitude (0.01-1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the T-e measurements are valid under harsh radiation conditions. This method to obtain T-e can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments. Published by AIP Publishing.