Electric potential measurement of the plasma plume in atmospheric-plasma jet

The electric potential along a long plasma column formulated inside the fine tube of glass or Teflon is measured by a high voltage probe.¹ An atmospheric plasma is generated into the fine tubes by a syringe electrode through which the gas is blown. The plasma jet is operated by the DC-AC inverter with a several tens of kHz. At the position of plasma column extended from the electrode applied by high-voltage, the plasma potential is measured to be high near the high voltage side while the potential decreases as the location becomes farther away from the high voltage electrode. If it is grounded at the end of glass tube, the plasma column voltage is measured to be about 0 V near the ground.