Plasma diagnosis system using multiple-reciprocating-pass thompson scattering

A plasma diagnosis system using multiple-pass Thomson scattering, comprising:

• a laser which supplies a laser pulse having predetermined polarization state and wavelength;
• an optical system configured to make the laser pulse multiple roundtrips along a predetermined optical path and focus the laser pulse to a predetermined location in plasma, and rotate a plane of polarization by 90 degrees after each complete roundtrip;
• a collection optics which is configured with a lens or a combination of lenses, collects lights scattered from a focal point in plasma, whereas the collected light by the vertical polarization of the laser pulse is referred to as ‘first collected scattering’ and the collected light by the horizontal polarization of the laser pulse is referred to as ‘second collected scattering’;
• and
• a polychromator which measures spectral characteristics of the first and second collected scatterings and outputs a Thomson scattering signal contaminated with a background noise and the background noise, respectively,
• wherein the background noise is generated by scattering in plasma due to stray lights and is obtained from the second collected scattering, and the Thomson scattering signal contaminated with the background noise is obtained from the first collected scattering.