The analysis of influence factors of impedance in inductively coupled plasma

Inductively coupled plasma (ICP) has become the most common ion source in analytical instruments. The characteristics of the plasma impedance, which are key parameters of the stability and efficiency of analytical instruments, can be easily influenced by the working environments. Therefore, there is an urgent need to investigate the impedance properties of the plasma. In this work, firstly, the ICP equivalent circuit model was established by combining the transformer model and the matching network model. Secondly, the expression of the ICP impedance were obtained by calculation. Finally, by changing the experimental conditions during ICP operation, the relationships between the plasma impedance and carrier gas, the cooling gas and the power were obtained, respectively. The results show that the impedance value of the inductively coupled plasma is very low, changing from 0.5Ω to 1.5Ω. In addition, the plasma impedance increases with the flow rate of the carrier gas, while, the plasma impedance decreases with the input power increases. And the impedance of the plasma was not influenced by the flow rate of the cooling gas.