Application of terahertz time-domain spectroscopy in atmospheric pressure plasma jet diagnosis

Abstract

The measurement of plasma density is of great significance in the study of magnetically constrained nuclear fusion and the transmission of electromagnetic waves in plasma. In this paper, the terahertz time-domain spectroscopy (THz-TDS) system is used to diagnose the plasma density of the atmospheric pressure plasma jet. The transmittance properties of the atmospheric pressure plasma jet are measured by a fiber-coupled transmission THz-TDS system. Then the electron density of the plasma jet is calculated based on the measurement results according to the relationship with the complex refractive index. The plasma jets with different electron densities are also investigated by varying the discharge voltages and the ionization gases. The terahertz transmittance spectra in measurement and calculation agree well. This study is of great significance for the applications of THz-TDS in high-accuracy, non-contact plasma diagnosis.