Helium I line intensity ratios in a plasma for the diagnostics of fusion edge plasmas

Helium I line intensity ratios obtained by a collisional radiative model, including new recommended excitation rate coefficients and the effects of hot electrons, enable us to measure electron density (n(e)) and temperature (T-e) in high density plasma. Measured n(e) and T-e using 492.2 nm (4 D-1-->2 P-1)/471.3 nm(4(3)S-->2 (3)p), 504.8 nn (4 S-1-->2 P-1)/471.3 nm, and 492.2 nm/504.8 nm line intensity ratios are in good agreement with the Langmuir probe results in the helium discharge plasma in the NAGDIS-I linear device (Nagoya University Divertor Simulator) for n(e) and T-e regions of 10(11)-4x10(12) cm(-3) and 5-20 eV. Hot electrons in the plasma are important for the He I line emissions when T-e is below the excitation energy approximate to 20 eV. A resonance scattering effect included in the calculation accounts for the experimental result of the enhanced 501.6 nm (3 P-1-->2 S-1) line emission. (C) 1996 American Institute of Physics.