A glow discharge plasma system for TDLAS calibration

The glow-discharge plasma static calibration system described in this study was meticulously designed to address the pressing need for Tunable diode laser absorption spectroscopy (TDLAS) measurements of concentration and temperature parameters involving non-stationary component such as oxygen and nitrogen atoms in the investigation of hightemperature gas effects. Employing high-frequency high-voltage alternating current (HF-HVAC), the system efficiently dissociates low-pressure gas within the discharge tube, swiftly generating a plasma rich in the targeted components. Notably, when a gas mixture consisting of 5% NO and 95% He is introduced into the discharge tube, and the output power of the discharge power supply is optimized to its maximum, alongside maintaining a gas pressure of 200 Pa within the discharge tube, the concentration of metastable oxygen atoms reach 3.66×109 cm-3. However, the detection of absorption peaks corresponding to N atoms was not feasible, attributed to the greater instability of N atoms compared to O atoms. In contrast, when a mixture containing 1% N2, 99% He, and trace amounts of air was introduced into the discharge tube, absorption peaks attributable to both O and N atoms were observed simultaneously. By adjusting both the gas pressure and discharge current within the discharge tube, precise control over the concentration of the targeted component is achieved, facilitating accurate calibration of the modulated laser absorption spectrum. The plasma system furnishes a potent instrument for diagnosing high enthalpy flow fields and contributes to the investigation of hightemperature gas effects.