Cinematic of the current sheet in a pulsed coaxial plasma source operated with uniform gas filling

Abstract

The evolution of the plasma obtained from magnetic probes and other electrical measurements in a coaxial gun with a Ti central electrode (cathode) used for coating studies in a mbar N 2 atmosphere is given. The results indicate that the currently used snowplough models adequately describe the cinematic of the plasma current sheet only if an additional mass to that of the gas between electrodes is included in the plasma sheet. The need to include extra mass is taken as evidence of relevant erosion of the central electrode, in accordance with the production of substantial coatings in similar devices. Evidence that sizeable portions of the discharge current remain attached near the end of the electrode system is presented, and some of the implications for the use of these devices for coating purposes are discussed.

Re-appraisal and extension of the Gratton-Vargas two-dimensional analytical snowplow model of plasma focus evolution in the context of contemporary research

“…It is then reasonable to explore whether this model can be extended to reproduce qualitative features of the sheath structure in the same operational regimes; this forms the focus of the next section. Conversely, when the GV model predictions do not match experimental data, it probably means that phenomena other than the snowplow effect are playing an important role; the discrepancy may then serve as a diagnostic tool [22].…”

“…The Buenos Aires Group has compared this model with experiments [21] and has shown a reasonably good agreement, which can be further improved in principle by incorporating adjustable parameters in the spirit of the Lee model [2]. This approach has been used to estimate electrode erosion in a coaxial gun [22] used for material coating applications. In spite of some of its positive features, the GV model has not been extensively used by DPF community.…”

“…A good illustration of the latter approach is found in the work of Bruzzone et.al. [22]. This paper aims to provide a re-appraisal of the work of Gratton and Vargas [20] and demonstrate its relevance to contemporary research in the altered context of widespread availability of cheap computing power and growing appreciation of commercial possibilities.…”

The polarity dependent effect of gyroviscosity on the flow shear stabilized Rayleigh–Taylor instability and an application to the plasma focus

“…We may make an estimate of effective case II model parameters based on PF system parameters via the planar ''snow plow'' model 15,16 of plasma accretion used in conjunction with a more detailed planar model 17 that provides self-similar solutions to the accretion layer's density profile. The former assumes that the layer is thin enough to neglect its internal structure for the purposes of overall momentum and mass conservation.…”

Toroidal High-Density Singularity in a Small Plasma Focus

“…During the displacement, the shape of the current sheath (CS) changes, inducing variations on the boundary conditions, the forces and the dissipation rates. Under certain circumstances, local instabilities that perturb the movement of the CS have been observed, leading to toroidal structures [1][2][3]. Lee et al [1] observed a toroidal structure in the CS, by means of electrical probes, in a 1.5 kJ Plasma Focus.…”