Performance of 20 cm audio frequency plasma column

In order to create a suitable plasma medium for electron acceleration in long plasma column, study has been made to reveal characteristics and factors affecting the extraction from gas discharge. The plasma is created in a Pyrex tube of 20 cm long, 4 cm diameter, with a power up to 170 W and frequency up to 100 kHz at low pressure of approximate 0.1 Torr. The plasma column is filled with different gases such as hydrogen, nitrogen and argon. The dependence of the extracted current on the discharge current is clearly apparent for both electrons and ions. The discharge and extracted currents of the present gases relative to that of hydrogen increases and decreases, respectively, with the increase of the gas mass number. The study of the extraction characteristics shows that the ion and electron currents could reach, approximate values of 1800 and 3000 μA, respectively, from hydrogen species. The increase of AF power, frequency and discharge pressure increases the extracted current but this increase is limited by plasma saturation and extraction perveance.