Line Ratio Spectroscopy of He-I Using ColRadPy on the Large Plasma Device

Indirect measurements of electron temperature, Te, and electron density, ne, using spectroscopy on the Large Plasma Device (LaPD) may provide a valuable diagnostic for machine users. In this work, the LaPD was set to a variety of mirror configurations with ne values ranging from 1e12 cm^-3 to 1e13 cm^-3 and Te values ranging up to 11 eV. The intensity of the He-I lines, 587.5 nm, 667.8 nm, and 706.5 nm, were individually measured using three monochromators and optical fibers coupled to the central region of the device. Simultaneously, a Thomson scattering system measured Te and ne at t = 12 ms into the discharge. The time resolved line emissions were then converted to the 587.5 nm/667.8 nm and 587.5 nm/706.5 nm ratios. The Python collisional radiative solver, ColRadPy [1], and the relevant He-I atomic data [2] were used to calculate predictions of Te and ne. The modeled plots indicate that within the experimental range the 587.5 nm/667.8 nm ratio is inversely related to Te and the 587.5 nm/706.5 nm is directly related to ne. Preliminary findings comparing line ratios to Thomson scattering measurements are promising and detailed results will be presented.

1. C.A. Johnson, et al. "ColRadPy: A Python collisional radiative solver." Nuclear Materials and Energy, Vol. 20, August 2019, https://doi.org/10.1016/j.nme.2019.01.013.
2. Summers, H. P. (2004) The ADAS User Manual, version 2.6 http://www.adas.ac.uk