Analysis of Argon Gas Plasma Density and Transmittance Characteristics by Terahertz Time-Domain Spectroscopy

The diagnostics of plasma density is of great significance. In this paper, a plasma diagnostic system by terahertz time-domain spectroscopy (THz-TDS) based on fiber laser is introduced. The plasma discharge is carried out by an inductively coupled plasma source (ICP). The corresponding electron density and the transmittance of terahertz wave through plasma are measured under different radio frequency (RF) power and different Argon gas pressure in the cavity. The electron density increases when the RF power is increased or the Argon gas pressure is increased. Furthermore, the transmittance of terahertz wave decreases when the RF power or the Argon gas pressure is increased. This experiment further expands the application ability of THz-TDS technology in the diagnostics of gas discharge plasma parameters, and provides an important reference for future applications in magnetic confinement nuclear fusion plasma.