Plasma diagnosis system using multiple-reciprocating-path thompson scattering

Abstract

Provided is a plasma diagnosis system using multiple-reciprocating-path Thompson scattering. The plasma diagnosis system includes: alight source which supplies pulsed laser beams; an optical system which sequentially supplies a pulsed laser beam in a vertical polarization state and a pulsed laser beam in a horizontal polarization state; a collection optic system which measures a first collection signal scattered from the plasma when the pulsed laser beam in the vertical polarization state is focused and measures a second collection signal scattered from the plasma when the pulsed laser beam in the horizontal polarization state is focused; and a controller which measures a Thomson scattering signal for the plasma by using the first and second collection signals measured by the collection optic system, and the second collection signal is a background scattering noise signal.

1 . A plasma diagnosis system using multiple-reciprocating-path Thomson scattering, comprising:
 a light source which supplies pulsed laser beams having predetermined polarization and wavelength;   an optical system which sequentially supplies a pulsed laser beam in a vertical polarization state and a pulsed laser beam in a horizontal polarization state by using the pulsed laser beams supplied from the light source;   a collection optic system which measures a first collection signal scattered from the plasma when the pulsed laser beam in the vertical polarization state supplied from the optical system is focused and measures a second collection signal scattered from the plasma when the pulsed laser beam in the horizontal polarization state supplied from the optical system is focused; and   a controller which measures a Thomson scattering signal for the plasma by using the first and second collection signals measured by the collection optic system,   wherein the first collection signal is a signal in which a Thomson scattering signal and a background scattering noise signal are mixed, and the second collection signal is a background scattering noise signal.   
     
     
         2 . The plasma diagnosis system according to  claim 1 ,
 wherein the optical system includes:   a polarizing beam splitter (PBS) which is disposed on an optical path of the pulsed laser beam supplied from the light source;   a first reflecting mirror which supplies the pulsed laser beams reflected from the PBS back to the PBS;   a Faraday rotator which is disposed on the optical path of the pulsed laser beam passing through the PBS and rotates the polarization state by 45 degrees and outputs the pulsed laser beam;   a focusing lens which focuses the pulsed laser beam supplied from the Faraday rotator on the plasma; and   a second reflecting mirror which reflects and supplies the focused pulsed laser beam back to the focusing lens, and   wherein the pulsed laser beam in the vertical polarization state and the pulsed laser beam in the horizontal polarization state are sequentially supplied to the plasma.   
     
     
         3 . The plasma diagnosis system according to  claim 1 , further comprising an optical isolator between the light source and the optical system, and
 wherein the optical isolator causes the pulsed laser beam supplied from the light source to propagate to the optical system but prevents the beam output from the optical system from entering the light source.   
     
     
         4 . The plasma diagnosis system according to  claim 1 , further comprising a trigger module which generates and outputs trigger signals when the pulsed laser beams in the horizontal polarization state and the pulsed laser beams in the vertical polarization state are supplied from the optical system, respectively, wherein the collection optic system is driven according to the trigger signals output from the trigger module. 
     
     
         5 . The plasma diagnosis system according to  claim 4 , wherein the trigger module is disposed between the light source and the optical system or at an arbitrary position of the optical system and generates and outputs the trigger signal when detecting that the pulsed laser beam is supplied from the light source to the optical system, detecting that the pulsed laser beam is supplied from the optical system to the plasma, or detecting that the pulsed laser beam is supplied at an arbitrary position of the optical system. 
     
     
         6 . The plasma diagnosis system according to  claim 1 , wherein the optical system focuses the pulsed laser beam into the plasma, the collection optic system collects and measures scattered optical signals in the plasma, and the controller measures and supplies the Thomson scattering signal in the plasma. 
     
     
         7 . The plasma diagnosis system according to  claim 1 , being applied to a plasma apparatus in which temperature and density of electrons are required to be measured.