Non-pertubative measurements of low and null magnetic field in high temperature plasmas

A system for non-perturbative measuring of radially varying axial magnetic fields in high-temperature field reversed configuration (FRC) plasmas, comprising:

• a first spectro-polarimeter comprising a spectrometer having a fast imaging Charged Coupled Device (CCD) camera;
• and
• a first light source positioned external to an FRC plasma and configured to radially inject a first plurality of laser beams into an FRC plasma and perpendicular to an FRC magnetic field confining the FRC plasma, wherein the FRC magnetic field is a radially varying axial magnetic field, wherein each of the first plurality of laser beams has a different polarization, wherein the first light source is configured to inject each of the first plurality of laser beams along a path crossing a null magnetic field location in the FRC magnetic field of the FRC plasma at two radial locations;
• wherein the spectrometer is configured to collect scattered light signals from plasma atoms illuminated by the first plurality of lasers beams in a viewing direction perpendicular to the injected paths of the first plurality of laser beams and one of radially or axially to the FRC magnetic field;
• and,
• wherein a null magnetic field location of the FRC magnetic field of the FRC plasma is determinable from the collected scattered light signals as a function of a linear polarization fraction, pL, of the collected scattered light signals, wherein the linear polarization fraction, pL, of a collected light signal being
• p
• L
• =
• 1
• 1
• +
• 4
• ⁢
• H
• 2
• when collected in a viewing direction axial to the FRC magnetic field, or
• p
• L
• =
• 1
• +
• 2
• ⁢
• H
• 2
• 1
• +
• 6
• ⁢
• H
• 2
• when collected in a viewing direction radial to the FRC magnetic field, wherein H=ωp/A is the ratio Larmor frequency of bound electron and Einstein's coefficient or radiation rate of the ion, and
• a plurality of slits each aligned with individual ones of the plurality of lasers beams to collect and image scattered light signals from plasma atoms illuminated by the plurality of lasers beams.