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An Analysis of a Stationary Copper Cathode Spot using Power Input to the Cathode
... Integrating the energy conservation equation for plasma gives this expression. Solving the equation of motion will be as follows [3,4]. ...
In vacuum breakers, the instability phenomenon occurs in the arc current at a current value before current cutting is generated. This arc phenomenon sometimes causes a current cutting due to this arc phenomenon. Therefore, it is the purpose of this report to capture the instability phenomenon due to vacuum arc discharge in the small-current arc region when cupper electrodes are used. A cathode spot model where a collision less sheath and collision plasma was connected to each other was constructed. A unique solution to the arc current (independent variable of discharge phenomenon) was obtained by simulation of dichotomy. As a result, it was supposed that the current that gives a real solution has a lower limit, the electrons that back-diffused from the collision plasma in cathode ion sheath exceed the ion under 19 A and the cathode spot that requires the existence of the ion sheath as a necessary antecedent or precondition does not exist anymore. It was concluded the non-existence of the cathode spot is connected the current instability phenomenon.
Instability phenomena of high-frequency vacuum arcs with an ∼100-kHz current waveform and active anodes were observed by using high-speed photography and optical emission spectroscopy and analyzed with a conventional theoreticalmodel. Our experimental and theoretical studies demonstrated that the instability mechanism for the transient vacuum arcs was completely different from that for the well-known quasi-stationary diffused arcs, where a cathode process predominantly contributes to the instability phenomena. In the case of the high-frequency vacuum arcs, the instability phenomena were mainly induced by a collaborative anode process operated by anodeevaporation and anode voltage drop.
An analysis is made of the effects of the fieldsof individual ions near the electrode sheath on the emission properties of thermionic cathodes. The field of corrections to the work function is calculated as a function of the ion position, and the distribution function is found for this correction. An equation is derived for the average density of the thermionic emission current.