Estimation of the plasma sheath thickness and particle number density in the axial phase of plasma coaxial accelerator

Al-Halim, Mohamed A. Abd

doi:10.1016/j.vacuum.2017.01.027

Cited by 13 publications

(6 citation statements)

References 40 publications

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“…Table II presents the peak and average values of density and temperature of the sheath when it reaches the end of the inner electrode for the extreme taper angle cases and the straight electrode. The temperature and density values obtained with this computational model are consistent with those reported on the literature for both simulations and experiments [32,[37][38][39]. Figure 9 shows the internal energy of the sheath when it reaches the end of the inner electrode as a function of taper angle.…”

Section: Effect Of Electrode Taper On Plasma Accelerationsupporting

confidence: 86%

“…However, reasonable estimates can be obtained without resorting to adding significant complexity to the computational model presented here. Following an approach reported in the literature [31,32], it is assumed that the sheath is a normal shock wave characterized by a shock pressure P S and velocity v S corresponding to each current sheath element. For convenience we will describe the case of diatomic molecules, and specifically the case of deuterium gas.…”

Section: Estimation Of Density and Temperature In The Current Sheathmentioning

confidence: 99%

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Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

2021

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A 2D computational model, incorporating the Snowplow approximation in the mass balance, is used to simulate the acceleration of an annular current sheath along two coaxial electrodes, with the inner one having either cylindrical or conical shape. The circuit, mass and momentum equations are simultaneously solved in 2D (r, z) considering initial breakdown along the insulator surface, ideal gas mass accretion by the current sheath (snowplow model) and distributed inductance along a coaxial transmission line short-circuited by the current sheath. Plasma density and electron temperature in the current sheath are estimated using standard planar shock theory. Numerical integration of the model’s equations for a given electrode geometry yields the temporal evolution of the current sheath parameters during the axial acceleration phase. In order to see the effect of the inner electrode shape on sheath parameters (i.e. transit time, kinetic energy, total mass, shape, etc.) and/or circuit properties (i.e. circuit inductance, voltage and current evolution, etc.), the portion of the inner electrode beyond the insulator was given a conical shape. By changing the cone slant in a range between ±5°, it was found that the current driven on the plasma sheath varies nonlinearly with the angle. The divergent (positive angle) electrode gives the sheath the highest kinetic energy, being twice the value corresponding to that of the straight inner electrode case, and the transit time is reduced from 1.34 to 1.20 µs. The estimates of plasma density and electron temperature indicate that the achievable ion densities are on the order of 4x1022 m-3, which corresponds to 30 % ionization, and typical temperatures at the end of the rundown phase are on the order of 8 eV. These values are comparable with those measured in experimental devices. The development of this tool will enable us to benchmark its results against an experimental installation currently close to being operational, and a future follow-up paper will be devoted to the comparison between the prediction of the rundown phase behavior and experimental results utilizing conical electrodes.

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Section: Effect Of Electrode Taper On Plasma Accelerationsupporting

confidence: 86%

Section: Estimation Of Density and Temperature In The Current Sheathmentioning

confidence: 99%

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

2021

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“…Effective charge (Z eff ) [31] and specific heat ratio (γ) [16] are calculated for nitrogen and neon gases using the corona model as follows:…”

Section: Spf Modelmentioning

confidence: 99%

Spherical plasma focus operated with nitrogen and neon gases for soft x-rays (bremsstrahlung radiation, line radiation, and radiative recombination)

2021

Plasma Phys. Control. Fusion

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X-ray emissions (bremsstrahlung radiation, line radiation, and radiative recombination) from spherical plasma focus (SPF) device are investigated with the developed spherical MHD model for nitrogen (N) and neon (Ne) gases with respect to gas pressure, which is varied from 0.1 Torr to 7 Torr. Ion density, plasma velocity, pinch temperature, and peak current are also calculated for N and Ne gases. The total capacitance, external inductance, charging voltage, and stored energy as the operational conditions of the SPF device in this study are 432 µF, 36 nH, 25 kV, and 135 kJ. The maximum current is achieved at 7 Torr for both N (1561 kA) and Ne (1525 kA). It is found that there is an optimum pressure point for both x-rays (bremsstrahlung radiation, line radiation, and radiative recombination) and the used gases (N and Ne), separately. While the optimum pressure of bremsstrahlung radiation for N and Ne gases are 0.9 Torr and 1 Torr, respectively, these optimum pressures of radiative recombination and line radiation are 1 Torr for N gas and 1.1 Torr for Ne gas, respectively. It is also found that line radiation constitutes the big portion of the soft x-ray (SXR) emissions from SPF device. Line radiations of N at 1 Torr and Ne at 1.1 Torr are 911 J (91% of total N SXRs) and 3036.5 J (93.1% of total Ne SXRs), respectively, which shows that SPF device can be considered as a good SXR source. Ion densities and peak currents at 7 Torr are calculated as 21.88 × 1023 m−3 with 1561 kA peak current for N gas and 15.98 × 1023 m−3 with 1525 kA peak current for Ne gas.

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“…A shock wave is generated and moved ahead of the CS when the CS motion is highly supersonic. The shock wave can be estimated by the following relation: 32,35)…”

Section: ( ) /mentioning

confidence: 99%

Experimental investigation of a low-energy linear plasma propulsion device

Ahmed¹,

Diab²,

Gaber³

et al. 2020

Jpn. J. Appl. Phys.

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This paper presents preliminary results for a new design of a pulsed linear plasma device that generates electromagnetic plasma propulsion. The current sheath dynamics and the plasma propulsion along an extension tube have been studied. Breakdown of helium gas occurs between coaxial electrodes when applying a high-voltage pulse. This paper presents measurements with a number of probes, as well as camera images of the plasma propagation. A plasma is ejected and fills a 40 cm length extension tube. Additionally, the measurements show that the length of the propelled plasma column and its intensity inside the expansion tube is increased by increasing the charging voltage, while the plasma propulsion current is decreased along the extension tube. It is noted that a lower critical time; 4.7 μs, is needed to ionize the gas and form the plasma current sheath.

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Estimation of the plasma sheath thickness and particle number density in the axial phase of plasma coaxial accelerator

Cited by 13 publications

References 40 publications

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

Spherical plasma focus operated with nitrogen and neon gases for soft x-rays (bremsstrahlung radiation, line radiation, and radiative recombination)

Experimental investigation of a low-energy linear plasma propulsion device

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