Doppler and Stark broadenings of spectral lines of highly excited helium atoms for measurement of detached recombining plasmas in MAP-II divertor simulator

摘要

The shapes of atomic helium spectral lines from various excited states were measured in the MAP (material and plasma)-II linear divertor simulator at the University of Tokyo, using a high-resolution visible-near-ultraviolet spectrometer with image magnification optics. A steady state pure helium plasma was produced by a direct current arc discharge in the volumetric recombination-dominated regime, where both the ionizing and the recombining components could be observed up to higher excited states. Highly excited states (principal quantum number n ≥ 6) of helium atoms are dominated by the recombining component, except the ~1P states that are optically coupled with the ground state. Therefore, we propose a method to determine the neutral temperature, electron density, and ion temperature in the recombining plasmas from the spectral line shapes with Doppler and Stark broadenings of three different transitions, 2~1S-3~1P (501.567 nm), 2 ~1S-7~1P (335.455 nm), and 2~3P-7~3D (370.500 nm).