Theory of the hollow cathode arc

Abstract

A theory of the hollow cathode arc is given which explains the physical mechanisms of operation of these discharges. The following basic phenomena are studied: the gas flow inside the cathode; the formation of the internal plasma column by ionization of the neutral gas by the primary electrons emitted by the cathode, which are accelerated in the cathode sheath; the transport of the ions towards the cathode wall; the transport of current and of kinetic energy towards the exit of the cathode, by the Maxwellian electrons of the plasma; and, finally, the thermal equilibrium of the cathode wall. This theory gives the axial variation of the gas pressure and wall temperature, the electron temperature, the mean number of excitations and of ionizations produced per primary electron, and the radial and the axial variation of the plasma density and plasma potential. The field-enhanced thermionic effect constitutes the basic emission mechanism of the cathode, the wall being heated mainly by ion bombardment. Theoretical results for discharges in argon with a tantalum cathode are in excellent agreement with all the available experimental results.

Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges

“…The ionization ratio obtained for the case under study exceeds 85%, and the extraction efficiencies of sputtered materials are found to be 3% and 17% for metal atoms and ions, respectively. The model also 18 reveals several physical processes of general interest for pulsed hollow cathode discharges: (1) There can be a significant increase in the extraction efficiency of ions as compared to neutrals due to a plasma-pressure-driven reversal of the electric field at the opening of the hollow cathode during the pulse. (2) Sputtered material is also extracted by an outwards-directed puff of process gas which continues long after the pulse.…”

“…Some examples are high power hollow cathode arcs [1,2], medium power hollow cathode glow discharges [3], and low power hollow cathodes used for space charge neutralization of the exhausts of plasma ion thrusters [4]. In the present work we combine the hollow cathode geometry with the recently developed technique of high power impulse sputtering, introduced 1999 when Kouznetsov et al [5] proposed it for magnetron sputtering.…”

“…Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges M I Saadeh (1,2) , I Pilch (2) , D Söderström (2) , D Lundin (1) , U Helmersson (2) and N Abstract. High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species.…”

The use of hollow cathodes in deposition processes: A critical review

“…Obviously, such high cathode temperatures also increase the gas temperature and this can enhance rarefaction near the cathode and produce important modifications to the plasma properties, gas-phase chemical reactions can cause significant heating of the substrates during thin film deposition [27,29]. The transition from HCD to HCA occurs rapidly when a threshold current density is reached and the new electron emission process become operative.…”

A hollow cathode arc as a high intensity beam source for ground state and metastable noble gas atoms in the eV translational energy range

“…Gas feed takes place through the cathode. Detailed theoretical studies on the operation of the hollow cathode have been performed by Ferreira and Delcroix (1978). Electrons are emitted by the hot cathode through thermoemission and are accelerated in a positive sheath at the inner cathode wall.…”