Study of formation mechanism of double metal plasma jets in a low-current pulsed vacuum arc discharge

Abstract

Plasma jet formation was studied in a vacuum arc configured with a conical cathode located inside a hollow cylindrical anode. The outside of this anode was insulated, except at a 0.4 mm diameter micropore. The grounded vacuum chamber also served as an anode. The hollow cylindrical anode was connected to the grounded chamber anode through a resistor R. 170 A 14 μs arcs were excited by a pulse generator comprised of a series connection of a 0.1 F capacitor bank charged to 12 kV, a 200 μH inductor, and a 30 Ω resistor. Two plasma jets formed during the arc discharge, one originating from the cathode tip and the other through the micropore. It was found that when R was increased from 0 Ω to 1 MΩ, (1) the plasma jet originating at the micropore weakened, (2) the peak current to the hollow cylindrical anode decreased from 73 A to 0, and (3) the peak arc current decreased from 176 A to 150 A. Plasma jet velocities for R = 0 were inferred from the difference between electron current peak times at two probes, to be 9 km/s for the plasma jet from the cathode and 27 km/s for the plasma jet at the micropore.

Double‐ejection micro‐cathode arc thruster applied to micro‐satellite

“…Taking into account the discussion above, the electron field emission [18,19] and Hump theory [20], and our previously obtained results [8], a simplified circuit diagram of the charged As shown in Figure 11, it was concluded that the operation mechanism of the AC d -µCAT was as follows [8]. First, when a high voltage was applied on the μCAT, a strong electric field E c formed on its cathode surface.…”

“…To quantitatively evaluate the directional ejection length of the plasma jet ejected from the insulating sleeve nozzle and produced by the different μCAT structures, light intensity distributions of the discharge images shown in Figure 3 were calculated using the simulation software of MATLAB [8]. As an example, for the AC s -µCAT structure, the calculated result based on Figure 3b is shown in Figure 4, where values of light intensity in the colour bar were dimensionless normalised data.…”

“…For the three μCAT structures described above, the metal cathodes and anodes were all composed of lead (Pb). Additionally, because part of the plasma that was emitted from the cathode flowed to and was absorbed by the grounded vacuum chamber wall during μCAT operation, the chamber also acted as an anode, collecting charged particles [8].…”

“…The current flowing to vacuum chamber (chamber current, I chamber (t)) was determined by I chamber (t) = I C (t) − I A (t). Plasma density and directional propagation speed were measured by using an improved Langmuir probe measurement method [8][9][10][11].…”

“…In our previous study focussing on the propulsion performance of a μCAT, we found that double clearly visible plasma jets (ejections), one generated near the cathode and the other one near the anode, were produced in a single shot by adopting the structure using an Ethylene Vinyl Acetate (EVA) micropore [8]. The propulsion performance of a μCAT could be improved by using double ejections [9,10].…”