Two step double layers in collisional anode plasmas
- Al.I. Cuzu Univ., Isai (Romania)
Nonlinear potential profiles with topologies of single and/or multiple layers can be experimentally investigated for nearly nonradiative but stiff collisional anode plasma in a discharge geometry shown in Fig. 1. Here both the time averaged ion concentration and the potential profiles of the large anode helium plasma were taken versus the axial position d{sub p}. This paper shows some of representative data obtained for a narrow transverse magnetic field, applied just at the open end (d{sub B{parallel}} = 0) of the cathode C (solid curves) together with those found for B{sub {parallel}} = 0 (broken curves). As a clear effect of this magnetic field, the {open_quotes}stairstep{close_quotes} profile of the plasma potential U{sub p} can be seen with the double layers localised near the axial boundaries of the active length of the hollow mesh-anode A{sub 2}. Since all of the voltage drops on the two double layers were still below the excitation potential of helium, the investigated anode plasma was practically a dark one. The same magnetic field only shifts the floating potential curve U{sub fl} towards little lower values, whereas the plasma potential between the potential hump of the first double layer and the second one remains practically unchanged. It is also shown that this first triple layer from the cathode end is well correlated spatially to the abrupt decrease of the ion saturation current I{sub i}{sup s} of the probe. Thus, in spite of the uniform cross-section of the hollow anode, the particle trapping in the magnetic field at the input section probably lead to certain current limitation so that some electric fields must be build up within the anode space to keep constant the charged particles flow. Therefore, we have proved that even in these higher pressure plasmas the single or multiple layers can be the result of the magnetic field action not only of the ionisation and excitation, as in the striations of the positive column or in the anode spots.
- OSTI ID:
- 212841
- Report Number(s):
- CONF-950749-; TRN: 96:010009
- Resource Relation:
- Conference: 22. international conference on phenomena in ionized gases, Hoboken, NJ (United States), 31 Jul - 4 Aug 1995; Other Information: PBD: 1995; Related Information: Is Part Of XXII International conference on phenomena in ionized gases. Contributed papers 2; Becker, K.H.; Carr, W.E.; Kunhardt, E.E. [eds.]; PB: 226 p.
- Country of Publication:
- United States
- Language:
- English
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