Abstract:Coaxial gun can produce high-speed and high-density plasma jet and has some potential applications in many research areas such as space thruster, space debris impact simulation, nuclear fusion, and material processing. The coaxial gun is usually composed of a pair of coaxial cylindrical and hollow electrodes. The pulsed discharge of coaxial gun has two discharge modes, i.e., deflagration mode and pre-fill mode. Compared with the pre-fill mode, deflagration discharge mode can induce a plasma jet with few impur… Show more
“…According to the NIST-ASD [42], the lines of atomic species were identified, where the suffixes I and II were, respectively, referred to the neutral and singly ionised state of each atom. The lines of the molecule and radical species in the spectra were confirmed from the published references [43-50]. Figure 11 OES spectra of discharge sparks during the PEF process.…”
Section: Resultssupporting
confidence: 68%
“…Owing to the electron-impact, ion-impact and thermal-impact dissociations in the plasma environment, the NH 4 + radicals might decompose as follows [45,50]: …”
Section: Discussionmentioning
confidence: 99%
“…The active species F* might also be a source of the marginal signal of the neutral F atoms in the OES spectra. Owing to the electron-impact, ion-impact and thermal-impact dissociations in the plasma environment, the NH 4 + radicals might decompose as follows [45,50]:…”
Section: Oes Analysis Of the Pef Dischargementioning
In this work, plasma electrolytic fluorination (PEF) was performed on AZ91 alloy in a nonaqueous NH 4 F-ethylene glycol (EG) electrolyte. The coating growth and the plasma discharge behaviour were investigated to understand the mechanism of PEF process. Results illustrated that the non-aqueous electrolyte determined the intrinsic characteristics of the PEF process, which resulted in the coating growth characteristics and plasma discharge behaviour distinct from those of a conventional PEO process. MgF 2 compound formed from the combination of the oppositely charged ions Mg 2+ from the substrate and F-form the electrolyte. The deposition of MgF 2 facilitated the growth of the PEF coating with an inward-growth characteristic. The discharge was characterised by a very small size and a weak intensity of the sparks, with an electron temperature (T e ) range of 3400∼3600 K. The three-type discharge model of conventional PEO processes was introduced to understand the mechanism of the PEF process.
“…According to the NIST-ASD [42], the lines of atomic species were identified, where the suffixes I and II were, respectively, referred to the neutral and singly ionised state of each atom. The lines of the molecule and radical species in the spectra were confirmed from the published references [43-50]. Figure 11 OES spectra of discharge sparks during the PEF process.…”
Section: Resultssupporting
confidence: 68%
“…Owing to the electron-impact, ion-impact and thermal-impact dissociations in the plasma environment, the NH 4 + radicals might decompose as follows [45,50]: …”
Section: Discussionmentioning
confidence: 99%
“…The active species F* might also be a source of the marginal signal of the neutral F atoms in the OES spectra. Owing to the electron-impact, ion-impact and thermal-impact dissociations in the plasma environment, the NH 4 + radicals might decompose as follows [45,50]:…”
Section: Oes Analysis Of the Pef Dischargementioning
In this work, plasma electrolytic fluorination (PEF) was performed on AZ91 alloy in a nonaqueous NH 4 F-ethylene glycol (EG) electrolyte. The coating growth and the plasma discharge behaviour were investigated to understand the mechanism of PEF process. Results illustrated that the non-aqueous electrolyte determined the intrinsic characteristics of the PEF process, which resulted in the coating growth characteristics and plasma discharge behaviour distinct from those of a conventional PEO process. MgF 2 compound formed from the combination of the oppositely charged ions Mg 2+ from the substrate and F-form the electrolyte. The deposition of MgF 2 facilitated the growth of the PEF coating with an inward-growth characteristic. The discharge was characterised by a very small size and a weak intensity of the sparks, with an electron temperature (T e ) range of 3400∼3600 K. The three-type discharge model of conventional PEO processes was introduced to understand the mechanism of the PEF process.
“…In this paper, the Stark broadening method is used to calculate the electron density [9,12,23,[25][26][27][28]. The fitted line as shown in figure 6(a) can be obtained by fitting the H β line in figure 5.…”
Section: Characteristics Of Plasmamentioning
confidence: 99%
“…This paper enumerates the parameters for density calculation. The specific method of Stark broadening calculation has been described in detail in other articles of the author [12,28]. The value obtained at this position is the largest density of plasma.…”
Plasma wall interaction (PWI) will occur inevitably during the operation of Tokamak. The coxial gun device has low operation cost and parameters of plasma produced by the gun are close to those of type I ELM, therefore, the coaxial gun is suitable in simulation experiment as heat-flux sources of transient events such as type I ELM under the condition of H-mode in ITER. In this paper, the plasma generated by the discharge of a tapered coaxial accelerator thermal shock on a tungsten target to simulate the damage effect of the divertor. The plasma parameters are measured in the experiment. The velocity of the plasma is 41.7 km/s, and the kinetic energy of a single hydrogen ion is 9.2 eV. The energy density at the center of the plasma can reach 1.5 MJ/m2, and the density can reach about 2.78×1015 /cm3. The reflection of plasma in the process of exposure at different angles is observed. It is observed that droplets of millimeter size splash from the target. Traces of liquid flow are observed on the surface of the target, which shows that there is a melting process on the surface of target. The mass loss of the target is in the order of mg after 20 pules. The ablation and residual stress of the target surface both decrease with the decrease of the angle. This is because the accumulated energy per unit area of the target surface decreases with the decrease of the angle. These results help us to better understand the damage effect of tungsten target for further research.
The transition from snowplow mode to deflagration mode of a parallel-plate plasma accelerator under gas-prefilled conditions is studied. The accelerator is powered by a sinusoidal-wave power supply with a first half-period current of 24.3 μs. The current distribution of the current conduction channel is measured by magnetic probes, the optical emission spectrum by a spectroscopic system, and the plasma optical intensity by photodiodes. The parallel-plate plasma accelerator does not form a thin current sheet, but a wide and diffuse current conduction region when the capacitors are charged to 8 kV and 13 kV. The discharge mode is a transition from snowplow mode to deflagration mode, from the current leading edge to the trailing edge. The plasma front region continuously sweeps and ionizes the neutral gas within a certain thickness, which is characteristic of snowplow mode, whereas the plasma tail region is a stationary current conducting channel maintained by ablating the copper electrodes, which is characteristic of deflagration mode. The transition mechanism from snowplow mode to deflagration mode might be breakdown caused by rail electrode overvoltage.
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