Laser scattering diagnostic system in Korea Research Institute of Standards and Science

The laser scattering system is installed in Korea Research Institute in Standards and Science (KRISS), which is well known diagnostics as the most accurate method for measuring electron temperature and electron density. Although it is challenging to measure the Thomson scattering signals in processing plasmas with low density and low temperature, each part of the system was carefully designed and aligned to maximize the collection efficiency as well as the spectral resolution. The frequency doubled Nd:YAG laser with the maximum energy of 1 J and the repetition rate of 10 Hz is adopted as a light source. The collecting optics transfers scattered photons into double-monochromators so that the highly resolved scattered spectrum would be recorded by intensified CCD. Both spectral and absolute calibration have been performed by measuring rotational Raman scattering spectra. The electron temperature and density are obtained from the spectral broadening and the intensity of the Thomson scattering spectrum, respectively. The system will be operated not only to study heating effects in various plasma sources, but also to compare the operating range and the accuracy of other diagnostics such as cut-off probes developed in KRISS.