On-demand density correction using steady-state plasmas in the LHD Thomson scattering

In order to measure reliable electron densities of fusion plasmas by using Thomson scattering system, both accurate absolute calibration and long-term stability in the system are required. Even if slight misalignment of some optics occurs, it may cause large errors in measured densities. We propose a new method to obtain correction factors to the errors originated from misalignment by using steady-state plasma discharges. In addition to the data correction, realignment of the laser beam can be applied also. (author)