LASER-INDUCED FLUORESCENT MEASUREMENTS OF MAGNETIC-FIELD CONTOURS IN A LOW-PRESSURE DISCHARGE

Faraday rotation of a laser beam and emission spectroscopy to resolve Zeeman splitting provide information about the plasma magnetic field, integrated along the line of sight. Information about the local magnetic field strength can be obtained using a dye laser tuned off the center of an atomic or ionic transition by an amount delta-lambda(Z). If the absorption linewidth of the transition probed is less than the Zeeman splitting, only those atoms/ions residing in a magnetic field where the Zeeman splitting is delta-lambda(Z) will resonantly absorb energy from the laser and fluoresce. The feasibility of this magnetic field contour technique was studied in a low-pressure neon discharge. A conductor insulated from the discharge generated a large magnetic field in the discharge free of the Stark broadening effects associated with large plasma currents. A focused-dye laser beam was propagated along a cord of the cylindrical discharge to avoid the conductor and glass tube on axis. The LIF intensity profile measured along the laser beams had peaks at those spatial locations where local magnetic fields, inferred from the conductor current, agreed with the Zeeman shifted wavelength of the laser.