Time-Lag Analysis of the Townsend Discharge in Argon with Activated Caesium Electrodes

Abstract

A study of the time-lag in a photoelectric, gas amplified discharge for parallel electrodes as a function of gas pressure, plate separation, and amplification has demonstrated that diffusion of metastable argon atoms is the source of the lag and that these atoms striking the activated caesium cathode are highly efficient in liberating secondary electrons. The Townsend ionization coefficients, a and 7, have been determined in the usual manner over an extended range of values of E/p 0 . Analysis of the time-lag function has made possible the separation of the number of secondary electrons released at the cathode into those due to positive ions and those produced by metastable argon atoms. A factor representing the fraction of electron energy gained in the field which is used to excite atoms to the metastable level has been determined as a function of E/po. The coefficient of diffusion of metastable argon atoms in argon has been computed and shown to be that expected for a metastable atom having a diameter effectively 1.74 that of the normal atom.

Quasi-Linear Elliptic Equations and Variational Problems With Many Independent Variables

“…When the secondary Y processes at the cathode are active, it is possible to show that in a rough general fashion the initial ionization current io for simplicity assumed liberated, from the cathode, is multiplied to a value i, by the field in terms of a relation of the general form, (2) which holds as long as r e x p Jadr < 1. Here the general symbol Ycan stand for any one of the three cathode processes or a composite of them.…”

Stability of the cathode layer of normal glow discharge in argon

“…For ionization of an argon atom with the electron shell 3p 5 4s the ionization rate constant near the cathode gives k * ion = 1.9 • 10 −7 cm 3 /c. In the argon case under consideration we have D * N a = (1.9 ± 0.3) • 10 18 cm −1 s −1 for metastable argon atoms in 3 P 2 and 3 P 0 states [14][15][16][17][18][19]. Finally we obtain for the reduced first Townsend coefficient near a copper cathode in argon…”

“…where D * is the diffusion coefficient of excited atoms, and we consider the depth of the cathode layer l to be small compared with the current radius that corresponds to the normal regime of glow discharge. According to experimental data [14][15][16][17][18][19] the reduced diffusion coefficient of excited argon atoms in states 3 P 2 and 3 P 0 in argon is equal to D * N a = (1.9 ± 0.3) • 10 18 cm −1 s −1 . As a result, according to formula (19), we obtain for the stepwise part α st of the reduced first Townsend coefficient…”

Composition and optoelectrical properties of sputtering MoSex films

“…The deposition rate increases first with the increase in the sputtering pressure from 0.3 to 0.7 Pa and then decreases when the sputtering pressure increases to 0.9 Pa. The variation law (0.3–0.7 Pa) can be explained by the following relations based on kinetic theory and discharge theory of gases 27 where is the mean free path of the gases, and j 0 is the current density. Equations (1) and (2) are defined by the following parameters: k (Boltzmann constant), T (temperature of the gas), d (diameter of the gas molecules), p (sputtering pressure), γ (Townsend ionisation coefficient), d c (the thickness of the cathode drop zone), ε 0 (vacuum permittivity), μ i (ion mobility) and V c (cathode fall).…”