Spectroscopic investigation of the time dependent Magnetic Field distribution in a plasma opening switch

Observation of the MF distribution in short duration plasmas is of major importance. This work presents time-dependent, spatially resolved, non-intrusive measurements of the Magnetic Field (MF) penetration into a Plasma Opening Switch (POS) experiment using observations of Zeeman splitting. In this experiment, a positive voltage pulse is applied to the inner conductor of a shorted coaxial POS, giving a peak current of 135 ± 10 kA with a quarter period of 90 ns. The interelectrode gap is 2.5 cm. In the measurements, the spectral profiles of the π and σ components of the line emission from the same volume element are observed in a single discharge, using two spectroscopic systems. It allows for unfolding the Doppler broadening from the Zeeman splitting. To obtain local measurements, the plasma is seeded with Ball ions, giving spatial resolution of ∼ 1 cm. Measurements of Stark broadening and line intensity time histories are used to verify that the seeded plasma does not affect the POS properties.