Patent Number: 
Section: claims

1. A non-perturbative method of measuring radially varying axial magnetic fields in high-temperature plasmas, comprising:radially injecting from one or more light sources a first plurality of laser beams into a Field-Reversed-Configuration (FRC) plasma and perpendicular to an FRC magnetic field confining the FRC plasma, wherein the one or more light sources being external to the FRC plasma and each of the first plurality of laser beams has a different polarization, wherein each of the first plurality of laser beams crossinga null magnetic field location in the FRC magnetic field of the FRC plasma at two radial locations as each of the first plurality of laser beams radially crosses the FRC magnetic field;collecting scattered light signals from plasma atoms illuminated by the first plurality of laser beams, wherein the scattered light signals are collected 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; anddetermining the null magnetic field location of the FRC magnetic field of the FRC plasma 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 where H=ωp/A is the ratio Larmor frequency of bound electron and Einstein's coefficient or radiation rate of the ion. 2. The method of claim 1, further comprising:axially injecting a second plurality of laser beams into the FRC plasma in a direction parallel to the FRC magnetic field, wherein each of the second plurality of laser beams crossing the null magnetic field location in the FRC magnetic field of the FRC plasma at two axial locations adjacent opposing axial edges of the FRC magnetic field as each of the second plurality of laser beams axially crosses the FRC magnetic field,collecting scattered light signals from plasma atoms illuminated by the second plurality of lasers, wherein the scattered light signals are collected in a viewing direction perpendicular to the injected paths of the second plurality of laser beams and radially to the FRC magnetic field;determining first and second axial null magnetic field locations of the FRC magnetic field of the FRC plasma 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        +                  2          ⁢                      H            2                                      1        +                  6          ⁢                      H            2                                ;andmeasuring a distance between the first and second axial null magnetic field locations to produce a length of the FRC magnetic field. 3. The method of claim 1, further comprising:radially injecting a second and a third plurality of laser beams into the FRC plasma in a direction perpendicular to the FRC magnetic field at first and second axial locations, respectively, adjacent first and second opposing axial edges of the FRC magnetic field;collecting scattered light signals from plasma atoms illuminated by the second and third plurality of lasers, wherein the scattered light signals are collected in a viewing direction perpendicular to the injected paths of the second and third plurality of laser beams and one of radially and axially to the FRC magnetic field;determining first and second axial null magnetic field locations of the FRC magnetic field of the FRC plasma 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; andmeasuring a distance between the first and second axial null magnetic field locations to produce a length of the FRC magnetic field. 4. The method of claim 1, further comprising:determining locations of the null magnetic field of the FRC magnetic field at two points along a diameter of the FRC plasma;calculating, using the locations of the null magnetic field, a radius and a center of the FRC plasma; andproviding the radius and center to a feedback control system. 5. The method of claim 4, wherein the feedback control system controls a radial location and size of the FRC plasma by controlling the externally applied magnetic field. 6. The method of claim 1, wherein the step of collecting scattered light signals from plasma atoms comprising:aligning a slit of a first spectropolarimeter 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 of the FRC plasma;collecting scattered light signals from plasma atoms illuminated by the first plurality of lasers through the slit; anddetermining the null magnetic field location of the FRC magnetic field of the FRC plasma from the collected scattered light signals as a function of the linear polarization fraction, pL, of the collected scattered light signals. 7. The method of claim 1, wherein the step of collecting scattered light signals from plasma atoms comprising:simultaneously aligning first and second slits of first and second spectropolarimeters in a viewing direction perpendicular to the injected paths of a second and third plurality of laser beams and one of radially or axially to the FRC magnetic field of the FRC plasma;collecting scattered light signals from plasma atoms illuminated by the second and third plurality of lasers through the first and second slits;determining a location of first and second axial null magnetic field locations of the FRC magnetic field from the collected scattered light signals as a function of the linear polarization fraction, pL, of the collected scattered light signals; andmeasuring a distance between the first and second axial null magnetic field locations to produce a length of the FRC magnetic field. 8. The method of claim 1, further comprising:determining locations of the null magnetic field of the FRC magnetic field at two points along a diameter of the FRC plasma;calculating, using the locations of the null magnetic field, a radius and a center of the FRC plasma; andproviding the radius and center to a feedback control system. 9. The method of claim 8, wherein the feedback control system controls a radial location and size of the FRC plasma by controlling the externally applied magnetic field. 10. 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; anda 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, anda 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. 11. The system of claim 10, wherein the first plurality of laser beams have similar wavelengths and are separated by a small distance from each other; and further comprising:a birefringent crystal to split the scattered light signals into orthogonal polarizations pairs of the scattered light signals; anda plurality of slits in the spectro-polarimeter, wherein each of the plurality of slits aligned with individual ones of the plurality of lasers beams to collect and image pairs of the orthogonal polarized scattered light signals with the CCD; andwherein the CCD is further configured to determine the null magnetic field location of the FRC magnetic field of the FRC plasma from the collected scattered light signals as a function of a linear polarization fraction, pL, of the collected scattered light signals. 12. The system of claim 10, further configured to:axially inject the second plurality of laser beams into the FRC plasma in a direction parallel to the FRC magnetic field, wherein each of the second plurality of laser beams crossing a null magnetic field location in the FRC magnetic field of the FRC plasma at two axial locations adjacent opposing axial edges of the FRC magnetic field as each of the second plurality of laser beams axially crosses the FRC magnetic field,collect scattered light signals from plasma atoms illuminated by the second plurality of lasers, wherein the scattered light signals are collected in a viewing direction perpendicular to the injected paths of the second plurality of laser beams and radially to the FRC magnetic field;determine first and second axial null magnetic field locations of the FRC magnetic field of the FRC plasma 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        +                  2          ⁢                      H            2                                      1        +                  6          ⁢                      H            2                                ;andmeasure a distance between the first and second axial null magnetic field locations to produce a length of the FRC magnetic field. 13. The system of claim 10, further configured to:radially inject a second and a third plurality of lasers into the FRC plasma in a direction perpendicular to the FRC magnetic field at first and second axial locations, respectively, adjacent first and second opposing axial edges of the FRC magnetic field;collecting scattered light signals from plasma atoms illuminated by the second and third plurality of lasers, wherein the scattered light signals are collected in a viewing direction perpendicular to the injected paths of the second and third plurality of laser beams and one of radially and axially to the FRC magnetic field;determining first and second axial null magnetic field locations of the FRC magnetic field of the FRC plasma 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; andmeasure a distance between the first and second axial null magnetic field locations to produce a length of the FRC magnetic field. 14. The spectro-polarimeter of claim 10, further configured to:determine locations of the null magnetic field of the FRC magnetic field at two points along a diameter of the FRC plasma;calculate, using the locations of the null magnetic field, a radius and a center of the FRC plasma; andprovide the radius and center to a feedback control system. 15. The spectro-polarimeter of claim 14, wherein the feedback control system controls a radial location and size of the FRC plasma by controlling the externally applied magnetic field. 16. The system of claim 10, further comprising:a second spectro-polarimeter comprising a spectrometer having a fast imaging CCD camera; anda second light source positioned external to an FRC plasma and configured to axially inject a second plurality of laser beams into the FRC plasma in a direction parallel to the FRC magnetic field, wherein the second light source is configured to inject each of the second plurality of laser beams along a path crossing a null magnetic field location in the FRC magnetic field of the FRC plasma at two axial locations adjacent opposing axial edges of the FRC magnetic field, wherein the spectrometer is configured to collect scattered light signals from plasma atoms illuminated by the second plurality lasers beams in a viewing direction perpendicular to the injected paths of the first plurality of laser beams and radially to the FRC magnetic field; and,wherein first and second null magnetic field locations adjacent the first and second opposing axial edges of the FRC magnetic field of the FRC plasma are 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        +                  2          ⁢                      H            2                                      1        +                  6          ⁢                      H            2                                .   17. The system of claim 10, further comprising:second and third spectro-polarimeters each comprising a spectrometer having a fast imaging CCD camera; andsecond and third light sources positioned external to an FRC plasma and configured to radially inject second and third plurality of lasers into the FRC plasma in a direction perpendicular to the FRC magnetic field at first and second axial locations, respectively, adjacent first and second opposing axial edges of the FRC magnetic field along a path crossing a null magnetic field location in the FRC magnetic field of the FRC plasma adjacent opposing axial edges of the FRC magnetic field, wherein each spectrometer of the second and third spectro-polarimeters is configured to collect scattered light signals from plasma atoms illuminated by the second and third plurality lasers beams in a viewing direction perpendicular to the injected paths of the second and third plurality of laser beams and one of radially and axially to the FRC magnetic field; and,wherein first and second null magnetic field locations adjacent the first and second opposing axial edges of the FRC magnetic field of the FRC plasma are 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.