Improvements of data quality of the LHD Thomson scattering diagnostics in high-temperature plasma experiments

Abstract

In Large Helical Device (LHD) experiments, an electron temperature (T e) more than 15 keV has been observed by the yttrium-aluminum-garnet (YAG) laser Thomson scattering diagnostic. Since the LHD Thomson scattering system has been optimized for the temperature region, 50 eV ≤ Te ≤ 10 keV, the data quality becomes worse in the higher Te region exceeding 10 keV. In order to accurately determine Te in the LHD high- Te experiments, we tried to increase the laser pulse energy by simultaneously firing three lasers. The technique enables us to decrease the uncertainties in the measured Te. Another signal accumulation method was also tested. In addition, we estimated the influence of high-energy electrons on Te obtained by the LHD Thomson scattering system. © 2010 American Institute of Physics.