Electrical Discharges in Gases. Part I. Survey of Fundamental Processes

Sheared Zonal Flow ExB Drifts Predicted from Emissive Probes and Measured by Laser‐Induced Fluorescence

“…Since at least the time of Langmuir [1,3], probes have been used to study basic plasma parameters including currents of the various species in plasmas. Emissive probes have found enduring utility in measuring the plasma potential [4]- [10].…”

Thermionic Electron Emission*

“…It is of interest to examine the modification of the equation due to this effect. It can be s~own that for V" > V, i = (2..fi/9)(e/m)l( V "I /R (32) X [1][2][3]/4 V" + 3/24(V ,/Vp ) 2 ••• ], (83) where V" is the applied potential between anode and negative end of the filament and V, is the total potential drop along the filament. In this equation V m = (-2.3Tk/e) log (i./i) = - (87) and (88) where V is the potential applied between cathode and anode corrected for the contact potential; V m is the value of the potential maximum measured with respect to the zero of potential previously defined; x the distance between cathode and anode; Xm the distance from the cathode to the potential maximum; T the temperature of the cathode; and i. the value of the saturation electron emission.…”

“…Thus, Tonks 17 has computed the following average values of S: For cubic facets or 100 planes, 1.500; for dodecahedral facets or 110 planes, 1.225; for 100 and 110 planes, 1.129. Some of the assumptions on which these values are based are: (1) The surface is covered with pyramids whose sides are crystal planes; (2) the orientation of crystal axes with respect to the surface is random; (3) for a given type of etch plane or planes, the facets occur in such a way as to give a minimum surface area. No one has made a thorough investigation to test these assumptions by experiment.…”

“…T HERE have appeared in the Reviews of Modern Physics two excellent summaries on thermionic emission, one by Compton and Langmuir 1 and one by Dushman. 2 Compton and Langmuir, while dealing primarily with discharge in gases, also discussed many phases of thermionic emission.…”

“…From these it follows that: (1) Either the number of free electrons must be small compared to the number of atoms and the mean kinetic energy per electron is (3/2)kT; or else, (2) the number of free electrons is of the order of the number of atoms but the kinetic energy increase per degree rise in temperature is much smaller for electrons than it is for atoms. The correlation of experiment and classical theory in the case of the optical properties, electrical conductivity, thermoelectricity, Thomson and Peltier effects lead to certain inconsistencies.…”