Extension of the measurable temperature range of the LHD Thomson scattering system

The large helical device Thomson scattering system was designed for the target electron temperature (T-e) range, T-e = 50 eV-10 keV. Above 10 keV, the experimental error becomes rapidly worse. In order to obtain reliable T-e data in the temperature range above 10 keV, we are planning to extend the measurable T-e range by following two methods. First we have installed one more wavelength channel that observes shorter wavelength region in polychromators. Next applying forward scattering configuration is another candidate. We estimate the data quality when the two methods are used. Both of the two methods are expected to improve T-e data quality at T-e >= 10 keV.(C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4740525]