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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:15 |
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Conference: Bucharest University Faculty of Physics 2003 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
Characterization of a DC plasma with hollow cathode effect
Authors:
A. R. PETRE, M. BĂZĂVAN, V. COVLEA, V.V. COVLEA, *ISABELA OPREA, ** H. ANDREI
Affiliation:
The University of Bucharest, Faculty of Physics,
*The University of Osnabrück,
**The University of Würzburg
E-mail
Keywords:
Abstract:
The cathode discharge tube has a plane parallel geometry with one cathode, two cathodes, respectively three plane cathodes. This has an inner diameter of 40 mm and two branches placed crosswise. One of them has two mobile electrodes with a length of 90 cm and other has two fixed electrodes with a length of 30 cm.
The hollow cathode is working in an abnormal regime of the glow discharge at increased ionization rate for relatively low discharge voltages. The HCDs (hollow cathodes discharges) are characterized, in conventional form, by cathode surface (planar, cylindrical, spherical or other geometry) which contain the negative glow while the anode is placed outside the discharge cavity. The modified hollow cathode discharge (MHCDs) has the anode inside the cavity. The fast electrons ionize and excite gas particles in the cathode region of a glow discharge which is essentially in HCE. Gunterschultze was the first to show that the HCE is due to the fast electrons accelerated in the cathode sheaths, and ellectrostically confined to oscillate between cathode surfaces. This is the so-called pendulum effect. Little and von Engel considered that enhancement from the cathode due to the ultra-violet radiation generated in the discharge has a major role in the HCE, while Pillow concluded that the role of photons and metastable is less significant. Today, is considered that the fast electrons are responsible for the dissipation of their energy – which acquired in the cathode space-charge sheaths – into the bulk plasma due the increasing of the ion which are incident on the cathode surface. Consequently, it occurs more -electrons are released in the secondary emission processes due to this ion bombardment and decreasing of the diffusion of charge carriers to the wall.
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