Self Consistently Generated Charge Cylinder in BETA Device

R. Kaur, A. Sarada Sree, S. K. Mattoo

Institute for Plasma Research, Gandhinagar, India.

DOI: 10.4236/jmp.2012.330208                

Abstract

This paper presents a study on near cathode space charge region in BETA (Basic Experiments in Toroidal Assembly), a toroidal plasma device with purely toroidal magnetic field. A charge cylinder has been found to be embedded in the plasma center corresponding to the hot filament cathode location in poloidal cross section. This charge cylinder has been created by the primary electrons emitted from the filament surface, which in turn, leads to the formation of a potential well in the core plasma. We have proposed a model, which shows that a tiny fraction of injected energetic electrons is sufficient to sustain the observed potential well. We have examined the equilibrium of the charge cylinder in poloidal cross-section and found that it exhibits equilibrium configuration by forming circulation pattern of primary electrons. The circulation pattern is formed by vertical drift due to toroidal magnetic field and self-consistent poloidal E×B drift. We have concluded that the self-consistency is in adjusting the poloidal drift to the vertical drift of the trapped primary electrons.

Keywords

Hot Cathode Discharge; Near Cathode Space Charge; Toroidal Magnetic Field

Conflicts of Interest

The authors declare no conflicts of interest.

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