Plasma plume is generated using a quartz tube, helium gas, and foil electrode by applying AC high voltage under the atmosphere. The plasma plume is released into the atmosphere from inside of the quartz tube and is seen as the continuous movement of the plasma bullet. The travel length of plasma bullet is defined from plasma energy and force due to electric field. The drift velocity of plasma bullet has the upper limit under atmospheric-pressure because the drift velocity is determined from the balance between electric field and resistive force due to collisions between plasma and air. The plasma plume charge depends on the drift velocity. Consequently, in the laminar flow of helium gas flow state, the travel length of the plasma plume logarithmically depends on the plasma plume charge which changes with both the electric field and the resistive force.

The atmospheric pressure plasma generated using a quartz tube, helium gas, and foil electrode by applying AC high voltage is investigated. A plasma plume is formed with a small bullet-like volume of plasma that travels at high speed inside of the quartz tube filled with a helium gas. The average movement velocity of the plasma bullet and the emitted light from helium plasma are observed inside the quartz tube. Both the average plasma bullet velocity and the power spectrum density (PSD) of the helium ion (He I) tend to decrease towards the tip of the plasma plume. The average plasma bullet velocity is linearly proportional to the PSD of He I. Therefore, the movement velocity of the plasma bullet is available to estimate from the PSD of He I at one measurement point.

No abstract