Effects of wire materials on radiative heat flux and spectral characteristics of a capillary discharge plasma jet

This paper deals with an experimental study of a copper wire explosion in air and water at atmospheric pressure. The influence of the stored energy, discharge type, ambient medium on the electrical and optical characteristics of a single wire explosion was examined and clarified. Particularly, optical emission spectroscopy as well as self-emission image diagnosis were conducted to understand the radiant and quenching process of the explosion. The results revealed that the radiation mainly contained two stages: a white light (continuous spectrum) flash soon after the moment of explosion, and a long period of line radiation of Cu ions/atoms in the following dozens of microseconds. By analysing characteristic lines, Cu2+ was found in the very early stage of the expansion of the discharge channel (DC). Besides, obvious line radiation of O and N ions/atoms was found when there existed a current pause. As for plasma parameters, the Boltzmann plot method indicated that the average temperature of explosion products was ∼1 eV, while the electron density experienced an apparent attenuation as the expansion of DC. In addition to this, the optical emission in air and water followed two distinctly different patterns, relating to the expansion of DC and diffusion of the ambient medium.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optical emission and quenching process of a Cu wire explosion: a spectroscopy study

Han

Zhu

et al. 2020

“…Overall, generator geometry has an important influence on the plasma mass density, and this is useful for some applications. For example, when simulating the hard disruption conditions of tokamak fusion reactors, a large AR generator will be useful for enhancing the energy density of the plasma jet [33].…”

Section: The Influence Of the Geometry On The Total Mass Densitymentioning

confidence: 99%

Investigation into geometric effect in capillary discharge plasma generator using an improved ablation model

Zhang¹,

Li²,

Chen³

et al. 2020

The wall material and the electrode material together determine the composition of the capillary discharge plasma. In this paper, an improved ablation model considering polyethylene (PE) and copper ablation and deposition was developed. Generators with different geometric sizes were calculated and tested. The results show that the concentration distributions of copper and PE in the generator were the pair-wise opposite, and the aspect ratio (AR) had a threshold (AR = 8.67). The copper mass density distribution varied from uniform to inhomogeneous with the increase in AR, which was similar to that of its concentration distribution. The maximum copper mass density increased with the increase in AR, and the AR threshold was also 8.67. The relationship between the copper or PE ablated mass and capillary length or diameter approximately followed a power law, and the relationship between the copper or PE ablated mass and AR approximately followed a proportional law. The PE mass density distribution was not similar to that of its concentration for AR ≥ 8.67. The PE ablated mass increased with the increase in AR, and its variation was similar to that of the maximum PE mass density. When the AR(AR > 5.2) was large enough, the PE mass density distribution determined the total mass density distribution. Otherwise, the total mass density distribution was determined by the mass density distribution of PE and copper. Overall, the simulation results were in good agreement with the experiments. These can be used to select the size and material of the capillary in simulating high heat flux plasma or electrothermal chemical gun ignition.

“…They found that the DC-water boundary has a significant influence on optical emission [28,29]. Yang et al reported the optical emission performance of plasma jet from a Cu/Ni wire-based capillary discharge [30].…”

Section: Introductionmentioning

confidence: 99%

Spatial–temporal evolution of plasma radiation in electrical wire explosion: a morphological observation

Han¹,

Zhu²,

Wu³

et al. 2020

This paper deals with an experimental study regarding the spatial–temporal evolution of single wire explosions in air and water at atmospheric pressure. Experiments were carried out with a microsecond timescale pulsed current source under 500 J stored energy. The morphology of the exploding wire with different discharge type, wire material, insulating coat, and ambient medium was intensively observed via self-emission images. The results revealed that the plasma radiation of wire explosion in air mainly contained two stages: initial intense radiation from optically thick plasma, and later decaying radiation from expanded arc-like plasma. A hollow structure was observed in a Cu exploding wire in air, and the plasma channel tended to develop inside it. As for W case, there would always be a core-corona structure, resulting in lower expansion rate and shock wave strength. Moreover, the plasma radiation of the underwater wire explosion was mainly determined by two factors: expansion rate and chemical reaction. The expansion rate of the radiant region in water was only 10–1 mm μs–1 level (1 mm μs–1 level for air), leading to the lagging radiation. No noticeable difference in morphology was found between Cu and W wire explosions in water. Particularly, the Al wire explosion generated a bright light emission due to chemical reactions. Finally, radiative characteristics in an exploding wire were preliminarily concluded and existing problems proposed.