Optical emission spectroscopy investigation of the current sheet in a small-bore parallel-plate electromagnetic plasma accelerator

Liu, Shuai; Huang, Yan; Zhang, Yongpeng; Wang, Zhan; Yu, Menghan; Yang, Lanjun

doi:10.1063/1.5055054

Cited by 7 publications

(2 citation statements)

References 39 publications

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“…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%

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Zhao¹,

Chen²,

Song³

et al. 2022

Plasma Phys. Control. Fusion

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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.

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Section: Characteristics Of Plasmamentioning

confidence: 99%

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Zhao¹,

Chen²,

Song³

et al. 2022

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…The canting current sheet then develops an axial component which produces a Lorentz force with a radial outward component, resulting in an accumulation effect of plasma mass in the cathode region [30,31]. Using photodiodes and optical emission spectrum, Liu et al [32,33] performed the measurement of the current sheet velocity and electron density at different propagation distances in a parallel-plate electromagnetic plasma accelerator. In addition, Poehlmann and Rieker et al [34,35] at Stanford University characterized the dynamics of the current distribution within the interior of a coaxial plasma gun and observed the evolution of the plasma operating in both the prefilled and gas-puff modes.…”

Section: Introductionmentioning

confidence: 99%

Effects of bias magnetic field on plasma ejection and dynamic characteristics of a coaxial gun operated in gas-puffed mode

Qi¹,

Song²,

Zhao³

et al. 2021

Plasma Phys. Control. Fusion

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The effects of bias magnetic field on the discharge characteristics of a coaxial gun and the parameters of ejected plasma are studied. At constant initial conditions (charging voltage, gas-puffed), magnetic probe data at different axial positions reveal the influence of the external bias magnetic field on the current distribution within the annular flow channel. Both photodiode signals and plasma radiation images show the plasma ejection characteristics. It is found that either applying or not applying the bias magnetic field results in two types of plasma with distinct ejection characteristics: spheromak or jet. By comparing the plasma parameters with and without bias magnetic field, it is found that the variation of jets velocity and momentum with discharge conditions are consistent with the snowplow model, whereas the spheromak plasma is subjected to a retarding force −J ϕ B r ⇀ z during the ejection, which decelerates the spheromak. Irrespective of the bias magnetic field, an increase in the discharge current amplitude leads to an elevation in electron density and temperature. The density of the spheromak is lower than that of the jet, but the temperature is higher. This is due to the fact that the electromagnetic focusing mechanism in the jet leads to a further increase in density, while the magnetic field lines stretched during the formation of the spheromak inhibit the focusing effect and expand freely after ejection. In addition, the magnetic field stretching process consumes part of the axial kinetic energy from the plasma and converts it into magnetic energy. The subsequent magnetic reconnection event causes the magnetic energy to be dissipated resistively by heating the plasma and then be converted into thermal energy. These results give us a better understanding in the interaction between plasma and magnetic field.

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Transition from snowplow to deflagration mode in a gas-prefilled parallel-plate plasma accelerator

Liu

Lin

et al. 2020

Physics of Plasmas

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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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Optical emission spectroscopy investigation of the current sheet in a small-bore parallel-plate electromagnetic plasma accelerator

Cited by 7 publications

References 39 publications

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Effects of bias magnetic field on plasma ejection and dynamic characteristics of a coaxial gun operated in gas-puffed mode

Transition from snowplow to deflagration mode in a gas-prefilled parallel-plate plasma accelerator

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