A new concept for polarimetric Thomson scattering diagnostics

Abstract

This paper proposes a new concept of polarimetric Thomson scattering diagnostics. Various studies show the polarization state of the scattered light from a laser pulse reflects electron temperature and the state can be measured with dedicated polarization tools. Since it does not require spectral measurements, it is believed that it could overcome an issue about unknown degradation in optical components, i.e., optical fibers and lenses, due to intense neutrons and γ-rays. Generally, a Thomson scattering diagnostic accompanies a laser beam linearly polarized in a direction perpendicular to the scattering plane. The new concept employs one additional laser polarization angle of which is parallel to the scattering plane. Taking the ratio of the two scattered intensities enables obtaining Te. The ratio is basically independent from the spectral transmission. This concept does not require any dedicated polarization tools. Calculations using designed parameters of a Thomson scattering system showed that the relative error in Te is less than 10% for Te= 5–40 keV. This paper also presents a way to calibrate different transmissions for polarization states using a gas scattering.