A first spectroscopic study of HFRC plasma

Abstract

An advanced spectral diagnostic system has been developed to measure the electron temperature (Te), elec-tron density (Ne), and ion temperature (Ti) for the Huazhong University of Science and Technology (HUST) field-reversed configuration (HFRC) plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny-Turner (C-T) monochromator equipped with both a 3600 g/ mm−1 grating and a 2400 g /mm−1 grating to achieve the measurement of line spectrum. Accompanying these components is an Electron-Multiplying Charge-coupled Device (EMCCD) camera to capture the spectral data. The relative intensity of the optical fiber spectrometer has been calibrated using a standard luminance source, and the spectrometer’'s wavelength calibration has been accomplished by a mercury argon lamp. This diagnostic setup has been configured to measure the electron density based on the Stark effect of Hγ (n = 5 → n = 2, 434.04 nm). Doppler broadening of an O III (2s22p(2P°)3p → 2s22p(2P°)3s, 375.988 nm) emission line is measured and analyszed to obtain the ion temperature, electron temperatures can be estimated from the relative strength of Hβ (n = 4 → n = 2, 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density is obtained from Stark effect measurements. Initial experimental results indicate that the highest electron temperature of the formation region is around 8 eV; the electron density of the col-liding-and-merging region is approaching 1020 m−-3 and the ion temperature reaches about 40 eV.