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 (ne) and temperature (Te) in high density plasma. Measured ne and Te using 492.2 nm (4 1D→2 1P)/471.3 nm (4 3S→2 3P), 504.8 nm (4 1S→2 1P)/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 ne and Te regions of 1011–4×1012 cm−3 and 5–20 eV. Hot electrons in the plasma are important for the He I line emissions when Te is below the excitation energy ≊20 eV. A resonance scattering effect included in the calculation accounts for the experimental result of the enhanced 501.6 nm (3 1P→2 1S) line emission.

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