Spectroscopic Investigation of Fast (ns) Magnetic Field Penetration in a Plasma

The time dependent magnetic field spatial distribution in a coaxial positive-polarity Plasma Opening Switch, carrying a current ~135 kA during ~100 ns, was investigated by two methods. In the first, ionic line emission was observed simultaneously for two polarizations to yield the Doppler and Zeeman contributions to the line profiles. In the second method, the axial velocity distribution of ions was determined, giving the magnetic field through the ion equation of motion. This method requires knowledge of the electron density, here obtained from the observed particle ionization times. To this end, a lower bound for the electron kinetic energy was determined using various line intensities and timedependent collisional-radiative calculations. An important necessity for POS studies is the locality of all measurements in r, z, and θ. This was achieved by using laser-evaporation to seed the plasma non-perturbingly with the species desired for the various measurements. The Zeeman splitting... The Zeeman splitting a..