Spectroscopic investigation of fluctuating anisotropic electric fields in a high-power-diode plasma

Fluctuating anisotropic electric fields in the anode plasma of a high-power ion diode are investigated as a function of time throughout the 100-ns-long voltage pulse by polarization spectroscopy of hydrogen lines. The H ± and H spectral profiles observed for different polarizations and lines of sight are compared to calculations, based on the quasistatic approximation, of the emission pattern resulting from the combined influence of the ionic and the turbulent electric fields. Assuming one-dimensional Rayleigh distributions for the turbulent field amplitudes, the difference between the linewidths observed for orthogonal polarizations yields mean amplitudes 5 kV/cm for the turbulent fields. Furthermore, accounting for the effect of the anisotropic fields on the spectral line profiles allows for a downward correction of the electron density obtained from the width of the Stark-broadened H line by a factor of 2. This in turn leads to a higher estimate of the electron temperature obtained from observed line intensity ratios and use of time-dependent collisional-radiative calculations.