Development of non-destructive method of plasma critical frequency determination

This study involves a development of non-destructive method of plasma critical frequency determination by conducting an experiment to compare the characteristics of metal and encapsulated plasma in fluorescent tube. Horn antennas are used to transmit and receive radio frequency from each other. The critical frequency of plasma is the point where the plasma changes in behaviour and behave like a metal when encounter with radio frequency. The device under test (DUT) for this experiment is formed using series of fluorescent lamps with 5 mm in diameter and warm white in colour. The fluorescent lamps are arranged in a row of 20 units and act as a plasma wall between the two horn antennas with separation distance of 200 cm. The experiment was conducted with different radio frequency values transmitted by the horn antenna, starts from 2 GHz to 18 GHz. The S-parameters performance for the plasma wall and metal sheet with similar dimension were analysed and based on experimental results it is concluded that the critical frequency of plasma is approximately 7 GHz. Therefore, plasma will exhibit its metallic behavior when incoming radio frequency is lesser than 7 GHz.