Bayesian Based Inference of Electron Temperature and Density by Using a Collisional-Radiative Model in Low Density Helium Plasmas

Optical emission spectroscopy technique with Bayesian probability theory is used to infer electron temperatures and densities of low density helium plasmas. Helium plasmas are generated in a newly developed DC multi-dipole chamber, MAXIMUS (Magnetic X-point sIMUlator System). Plasma parameters are varied by adjusting neutral pressure, bias voltage and heating current. Likelihoods are calculated based on a helium collisional-radiative model consistent with the measured signal and noise level. With a uniform prior probability, we obtain the posterior which are compared with the simultaneous and independent measurements of the electron temperature and density by Langmuir probes.