First spectroscopic study of HFRC plasma

An advanced spectral diagnostic system was developed to measure the electron temperature (T_e), electron density (N_e), and ion temperature (T_i) of the Huazhong University of Science and Technology field-reversed configuration plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny–Turner monochromator equipped with both a 3600 g mm⁻¹ grating and a 2400 g mm⁻¹ grating to measure the line spectrum. Accompanying these components is an electron-multiplying charge-coupled device camera to capture spectral data. The relative intensity of the optical fiber spectrometer was calibrated using a standard luminance source, and the wavelength calibration of the spectrometer was accomplished using a Hg/Ar lamp. This diagnostic setup was configured to measure electron density based on the Stark effect of H_γ (n = 5 → n = 2; 434.04 nm). Doppler broadening of an O III (2s²2p(²P⁰)3p → 2s²2p(²P⁰)3s; 375.988 nm) emission line was measured and analyzed to obtain the ion temperature, and electron temperatures were estimated from the relative strength of H_β (n = 4 → n = 2; 486.14 nm) (D_β) and H_γ (D_γ) spectral lines when the electron density was obtained from Stark effect measurements. The initial experimental results indicate that the highest electron temperature of the formation region was approximately 8 eV, the electron density of the colliding-and-merging region was approaching 10²⁰ m⁻³, and the ion temperature reached about 40 eV.