The bottleneck in pseudospark discharges

Abstract

Physical mechanisms during early phases of pseudospark discharges are still under discussion. Experiments at low rates of current rise (dI/dt<109 A/s) were performed to investigate these phenomena, using filtered fast shutter photography of the discharge plasma in the visible wavelength region. Additionally temporally resolved measurements of line emission of the filling gas (hydrogen and helium) and cathode material (copper) were performed. These experiments revealed a discharge phase where the cathode surface involved in the discharge is restricted mainly to the inside of the cathode aperture. The voltage drop during that phase is about 200–400 V and the current density exceeds 1 kA/cm2. A possible explanation of the discharge mechanisms during that discharge phase is self-sputtering of cathode material from the cathode surface inside the cathode aperture. The described mechanisms might be fundamental for the transition from the transient hollow cathode phase to the high current phase in pseudospark discharges.

Arc erosion characteristics of pseudospark discharge in multiaperture geometry

“…Refined model calculations 22 showed enhanced sputtering yields in contrast to earlier estimates 17 when presence of metal vapor ͑cathode atoms͒ between the cathode and the plasma sheath is taken into account. Presence of metal vapor in pseudospark discharge plasma has been verified experimentally 3,4,23 and it probably arises because of heating of the cathode microtips due to ion bombardment. 24 A sputtered atom that is released from the cathode due to ion impact can return to the cathode after it is ionized by the plasma and can cause release of further cathode atoms over a series of cycles, leading not only to an enhancement of the bulk plasma density but also to a decrease in the mean ionization length.…”

“…Experiments have unambiguously identified the superdense glow as distinct from the high-current arc mode. 3,4 The fine structure in the voltage drop arising due to this discharge phase, however, is only visible at low currents and low-current rise times. 3 Because of its remarkable properties such as current conduction in a homogenous discharge and high-current rise times, the pseudospark is well suited as a low-erosive fast-closing switch, besides other applications such as generation of x-rays 5 and microwaves 6 and production of high-intensity electron beams for free electron lasers 7 and material processing.…”

“…3,4 The fine structure in the voltage drop arising due to this discharge phase, however, is only visible at low currents and low-current rise times. 3 Because of its remarkable properties such as current conduction in a homogenous discharge and high-current rise times, the pseudospark is well suited as a low-erosive fast-closing switch, besides other applications such as generation of x-rays 5 and microwaves 6 and production of high-intensity electron beams for free electron lasers 7 and material processing. 8 However, the low-erosive nature of pseudospark conduction is reported to vanish above a threshold current limit of about 45 kA, 9 with enhanced electrode erosion resulting due to discharge collapse into the arc mode, severely affecting device performance.…”

Investigation of the high current stages in pseudospark discharge

“…D = 3 mm, h = 4 mm. Assuming  = 0,2 we substitute the values in (5). We find that the left and right sides differ from each other about twice.…”

“…At present, the discharge is widely used in the development of high current switching, generation of extreme ultraviolet radiation and so on [1][2][3]. It is known that the discharge during of its development goes through several stages, each characterized by its localization in the plasma electrode system and apparently by current transport mechanism [4][5][6]. However, if the physical processes in the prebreakdown, low-current stage adequately studied [7,8], while the study of high current stages of dense and superdense glow discharges a number of issues appear.…”