Pulsed low-pressure wire discharge

Abstract

A pulsed low-pressure wire discharge was studied experimentally. One can clearly distinguish at least three very different phases in the discharge development. During the breakdown lag the ionization takes place principally near the wire anode. The cathode secondary emission under ionic bombardment begins to play a (minor) role throughout the low-current non-steady-state phase since the cathode sheath is not yet formed. Once the sheaths are formed, the hollow-cathode discharge develops. The stability of a hollow-cathode discharge with an immersed small-size wire anode was analyzed. It is shown that the ratio of electrode surfaces Scathode∕Sanode necessary for uniform discharge formation depends on secondary emission yield, the nature of gas, and anode geometry. If the stability condition is violated, a double anode sheath appears and discharge becomes unstable.

Particle Modelling of Low-Pressure High-Current Wire Discharge

“…From the statistics point, the behaviour of both groups of energetic electrons is very alike. The elastic scattering dominates, ionization follows, while the less effective process is the excitation (‘dim glow’ as experimentally observed2,4,10). This is due to the trajectory deviation induced by the anode sheath, without capture of fast electrons.…”

“…As mentioned in the PIC‐MCC section, the thermalized electrons dominate the eepf and, as found, 90% of them are captured at the anode if they travel around. This result was already postulated and used to develop the stability condition of the WD,10 but it is also now numerically proved.…”

“…In spite of the measurements of some global plasma characteristics,6 the comprehension of this type of discharge is far from being achieved until the last decade, when systematic experimental studies have been performed 7–9. Recently, important advances explaining the WD behaviour have been reported on its temporal evolution and the related stability criterion 10…”

Particle in cell modelling of the observed modes of a dc wire discharge

“…Makarov [9] used the same approach to describe one state of its pulsed wire discharge. Those analyses rely on the hypothesis that the discharge can be on first approximation considered as an unipolar current of Helium ions.…”

“…Most of the studies have been devoted to pulsed WIPS which can develop current density of about one Ampere per centimeter length, being therefore a good candidate as ion source for high current electron gun [3,6,7,8]. Recently, Makarov undertook both an experimental [9] and a 1D numerical study [10,11] of a high current pulsed WIPS and the temporal evolution of the discharge.…”