Plasma plastic cleaning machine Langmuir oscillation and oscillation frequency

Plasma plastic cleaning machine Langmuir oscillation and oscillation frequency:

A strong electric field will be generated when the charge is separated in the plasma due to the thermal motion of particles, but the macro neutral plasma of plasmas cleaning machine has a strong recovery trend. Because of the small mass of electrons in plasma, the motion of electrons is the fundamental cause of the collective motion of plasma. The following is an example of one-dimensional motion. Suppose an electron in a region moves with the same speed in the x direction to produce a displacement δ, so that a surplus of positive and negative charges will appear on both sides of the region, thus generating an electric field E.

The direction of the electric field is to pull the electrons back to the equilibrium position in order to restore the electrical neutrality of the plasma of the plasma plastic cleaning machine. However, due to inertia, electrons do not stop at the equilibrium position, but rush through the equilibrium position and reverse their displacement. This in turn causes the charge to separate in the opposite direction, creating a reverse restoring electric field, which pulls the electrons back again and pushes them over the equilibrium position. Over and over, the electrons oscillate collectively around the equilibrium position. Because the ion mass is large and the response to the change of electric field is slow, it can be considered to be immobile and still be regarded as a uniform positive back base. The space charge oscillation that occurs when such neutrality is destroyed in a plasma. It is also known as the Langmuir oscillation because it was Langmuir who first discovered it. Langmuir oscillation is one of the inherent characteristics of plasma and its oscillation frequency is called "plasma frequency".

The physical significance of Langmuir oscillation period is as follows:

(1) The plasma in the plasma plastic cleaning machine can prevent the charge separation caused by the thermal motion of particles, and the oscillation period is the time when the plasma stops the charge separation and turns into Langmuir oscillation;

(2) the oscillation period is a small time scale on which the plasma's electroneutral condition is established, and the plasma is macroscopic electroneutral only within the time interval of t>tp;

(3) the oscillation period is the lower limit of the plasma existence time, that is, the plasma duration time t>>tp.