Extinguishment of hot cathode discharges by space-charge and surface magnetic effects

Emission characteristics of a directly heated, rod-shaped LaB6 hot cathode has been studied in a multi-dipole confinement device. It is found that contrary to predictions from the conventional space-charge limited emission theory, emission current is not simply limited to a maximum value but eventua...

Full description

Saved in:
Bibliographic Details
Published in:Plasma sources science & technology 2020-11, Vol.29 (11), p.115021
Main Authors: Yip, Chi-Shung, Jin, Chenyao, Zhang, Wei, Xu, Guo Sheng, Hershkowitz, Noah, Severn, Greg
Format: Article
Language:English
Subjects:
hot cathode
sheaths
thermionic emission
virtual cathode
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Emission characteristics of a directly heated, rod-shaped LaB6 hot cathode has been studied in a multi-dipole confinement device. It is found that contrary to predictions from the conventional space-charge limited emission theory, emission current is not simply limited to a maximum value but eventually extinguished by space-charge related effects. In addition, directional preference of electron emission towards the positive lead of the applied heating voltage can be visibly observed. Results suggest that thermionically emitted electrons trapped in the virtual cathode are pumped towards the high voltage lead of the applied heating, and that the magnetic effects for filament heating currents exceeding 50 A may be the underlying mechanism of extinguishment; that is, the gyromotion of surface emitted electrons for sufficiently great heating currents may prevent electrons from escaping the virtual cathode. Geometrical effects are also briefly discussed.
ISSN:0963-0252
1361-6595
DOI:10.1088/1361-6595/abbdc9