LASER INDUCED FLUORESCENCE MEASUREMENTS OF MAGNETIC FIELD CONTOURS IN HIGH CURRENT DEVICES

THE DISTRIBUTION OF THE MAGNETIC FIELD IN A HIGH CURRENT PLASMA DEVICE PROVIDES IMPORTANT INFORMATION ABOUT THE DEVICES OPERATION. TRADITIONAL FARADAY ROTATION, ZEEMAN EMISSION SPECTROSCOPY, AND MAGNETIC PROBE TECHNIQUES SUFFER FROM POOR SPATIAL RESOLUTION BECAUSE THE MAGNETIC FIELD EFFECT IS INTEGRATED ALONG THE LINE OF SIGHT FOR THE OPTICAL TECHNIQUE AND THE PROBES PERTURB THE PLASMAS. A LASER INDUCED FLUORESCENCE (LIF) TECHNIQUE IS PROPOSED TO MEASURE THE SPATIAL AND TEMPORAL EVOLUTION OF CONSTANT MAGNETIC FIELD CONTOURS IN THESE DEVICES. THIS TECHNIQUE UTILIZES A DYE LASER TUNED TO A ZEEMAN SHIFTED ELECTRONIC TRANSITION FREQUENCY TO LOCALLY EXCITE THE TARGET ATOMS/IONS TO A HIGHER ENERGY STATE. THE INTENSITY DISTRIBUTION OF THE EMITTED RADIATION EMITTED PERPENDICULAR TO THE BEAM IS A MEASURE OF THE LOCATION OF THE MAGNETIC FIELD CONTOUR IN THE PATH OF THE LASER. A STREAK CAMERA CAN BE USED TO MEASURE THE TEMPORAL MOTION OF THE CONTOURS AND A FRAMING CAMERA CAN BE USED TO RECORD THE SPATIAL PROFILE OF THE CONTOURS. MORE THAN ONE MAGNETIC FIELD CONTOUR CAN BE SIMULTANEOUSLY RECORDED USING AN ELECTRONIC TRANSITION HAVING A COMPLEX ZEEMAN SPECTRUM. THE TECHNIQUE IS APPLICABLE TO MEASURE LARGE MAGNETIC FIELDS (10 GK - 1 MG) WHEN THE ZEEMAN SHIFT IS LARGE COMPARED TO THE ABSORPTION LINEWIDTH OF THE TRANSITION PROBED.