Resonant behavior of the electron component of the plasma and stratification of the positive column of a gas discharge

Abstract

Abstract A new point of view on the appearance of S-, P- and R-striations in a positive column of inert gases is proposed, based on a dynamic analysis of the resonance properties of phase trajectories of electrons in spatially periodic fields. The area of applicability is focused on DC discharge in inert gases at low pressures. The motion of electrons associated with the gain of energy in the field E 0 up to the excitation threshold ɛ ex and the abrupt loss of this quantum of energy leads to the appearance of a spatial scale L 0 = ɛ ex/(eE 0). Analysis of motion in sinusoidally modulated fields shows the presence of resonant fields containing the fundamental mode L 0, which corresponds to the S-striation, and higher harmonics associated with integer and non-integer resonances. In particular, a resonant field with a period length L P = L 0/2 corresponds to a P-striation, and a resonant field L R = 2/3L 0 to an R-striation. Thus, the positive column can be viewed as a resonator containing a set of resonant fields. Like a tuning fork, it responds to a disturbance of one of the modes, in particular, by the appearance of S-, P-, or R-striations, depending on the discharge conditions. The acuity of the resonances is analyzed as a function of the detuning from the resonant fields. The spectrum of integer and non-integer resonances is given. It is shown that resonances corresponding to S-, P-, and R- striations have the highest amplitude. The dynamic and kinetic approaches to the description of striations are compared. The dynamic approach to some extent eliminates the difficulties of the kinetic theory associated with the long settling length of the solution to the Boltzmann equation, which is much larger than the length of the positive column.