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Journal articles on the topic 'PLASMA SHEATH'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 January 2023

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1

Shaikh, Zubair I., Anil N. Raghav, Geeta Vichare, Ankush Bhaskar, and Wageesh Mishra. "Comparative statistical study of characteristics of plasma in planar and non-planar ICME sheaths during solar cycles 23 and 24." Monthly Notices of the Royal Astronomical Society 494, no. 2 (April 22, 2020): 2498–508. http://dx.doi.org/10.1093/mnras/staa783.

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ABSTRACT Planar magnetic structures (PMS) are often observed in sheath regions driven by interplanetary coronal mass ejections (ICMEs) and in corotating interaction regions (CIRs). Here, we study plasma properties statistically within planar and non-planar ICME sheath regions using in situ data from the Advanced Composition Explore (ACE) spacecraft. The study includes 420 ICME-driven sheaths from 1998–2017. We found that 146 ($\sim 35{{\ \rm per\ cent}}$) ICME-driven sheaths are planar, whereas 274 ($\sim 65{{\ \rm per\ cent}}$) are non-planar. This study found that the average plasma temperature, density, speed, plasma beta, thermal pressure and magnetic pressure are higher in planar sheaths than in non-planar sheaths. This implies that high compression plays an essential role in the formation of PMS in sheath regions. Interestingly, our analysis reveals explicitly that the strength of the southward/northward magnetic field component is almost double in planar sheath regions compared with non-planar sheath regions. This suggests that planar sheaths are more geoeffective than non-planar sheaths.

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2

Das, G. C., R. Deka, and M. P. Bora. "Revisiting the plasma sheath—dust in plasma sheath." Physics of Plasmas 23, no. 4 (April 2016): 042308. http://dx.doi.org/10.1063/1.4946865.

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3

Ala-Lahti, Matti M., Emilia K. J. Kilpua, Andrew P. Dimmock, Adnane Osmane, Tuija Pulkkinen, and Jan Souček. "Statistical analysis of mirror mode waves in sheath regions driven by interplanetary coronal mass ejection." Annales Geophysicae 36, no. 3 (May 24, 2018): 793–808. http://dx.doi.org/10.5194/angeo-36-793-2018.

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Abstract. We present a comprehensive statistical analysis of mirror mode waves and the properties of their plasma surroundings in sheath regions driven by interplanetary coronal mass ejection (ICME). We have constructed a semi-automated method to identify mirror modes from the magnetic field data. We analyze 91 ICME sheath regions from January 1997 to April 2015 using data from the Wind spacecraft. The results imply that similarly to planetary magnetosheaths, mirror modes are also common structures in ICME sheaths. However, they occur almost exclusively as dip-like structures and in mirror stable plasma. We observe mirror modes throughout the sheath, from the bow shock to the ICME leading edge, but their amplitudes are largest closest to the shock. We also find that the shock strength (measured by Alfvén Mach number) is the most important parameter in controlling the occurrence of mirror modes. Our findings suggest that in ICME sheaths the dominant source of free energy for mirror mode generation is the shock compression. We also suggest that mirror modes that are found deeper in the sheath are remnants from earlier times of the sheath evolution, generated also in the vicinity of the shock. Keywords. Interplanetary physics (plasma waves and turbulence; solar wind plasma) – space plasma physics (waves and instabilities)

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4

Main, Geoffrey L., and S. H. Lam. "A general solution condition for collisionless sheaths." Journal of Plasma Physics 38, no. 2 (October 1987): 287–300. http://dx.doi.org/10.1017/s0022377800012587.

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A general solution condition for collisionless sheaths is developed. Previous work has assumed that the Bohm criterion or the generalized Bohm criterion ensures a self-consistent sheath solution. This paper shows that for nonmonotonic collisionless sheath structures, such as double sheaths containing trapped ions, the generalized Bohm criterion is a necessary but not a sufficient condition. The general solution condition developed is always sufficient and the generalized Bohm criterion is shown to be special case of it. The general solution condition is applied to a double emitter sheath containing trapped ions. First, it is shown that the low-energy part of the plasma ion distribution coming into the sheath cannot be neglected as claimed in some analyses, because the shift in mean ion velocity through the pre-sheath (generalized Bohm speed) depends strongly on low-energy ions. Second, it is shown that the presence of trapped ions moves the point of critical self-consistency away from the collisionless sheath-neutral plasma asymptotic match and into the collisionless sheath. Consequently, both the sheath structure and the generalized Bohm speed depend on the amount of trapped ions. Thus collisional effects may dominate the structure of a presumably collisionless sheath through the trapping mechanism and the collisional pre-sheath which determines the low-energy ion component entering the collisionless sheath.

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5

Riemann, K.-U. "Plasma and sheath." Plasma Sources Science and Technology 18, no. 1 (November 14, 2008): 014006. http://dx.doi.org/10.1088/0963-0252/18/1/014006.

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6

Xing, Yunqi, Yixuan Wang, Jiakai Chi, Haoliang Liu, and Jin Li. "Study on Improving Interface Performance of HVDC Composite Insulators by Plasma Etching." Coatings 10, no. 11 (October 27, 2020): 1036. http://dx.doi.org/10.3390/coatings10111036.

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High-voltage direct-current composite insulators are faced with various challenges during operation, such as creeping discharge, umbrella skirt damage, abnormal heating and insulator breakage. Among them, the aging of the interface between the core rod and the sheath is one of the important causes of composite insulator failure. In order to improve the electrical resistance of the composite insulator interface, this study uses plasma etching to modify the surface of the glass-fiber-reinforced epoxy resin plastic to prepare the high-voltage direct-current composite insulator core rod–sheath samples. By analyzing the surface morphology of the epoxy resin, static contact angle and surface charge transfer characteristics, the control mechanism of the plasma etching treatment on the interface bonding performance and leakage current of composite insulator core rod–sheath samples were studied. The results show that proper etching time treatment can improve the trap energy level distribution and microstructure of epoxy resin and increase the discharge voltage along the surface; chemical bonding plasma etching can improve the interfacial bonding performance of core rod–sheath samples sheaths, reduce the leakage current of composite insulator core rod–sheath samples sheath specimens and improve their interfacial performance.

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7

Lavine, E. S., S. V. R. Rocco, W. M. Potter, J. Angel, E. Freeman, J. T. Banasek, J. Lawson, et al. "Measurements of the imploding plasma sheath in triple-nozzle gas-puff z pinches." Physics of Plasmas 29, no. 6 (June 2022): 062702. http://dx.doi.org/10.1063/5.0084352.

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Gas-puff z-pinch implosions are characterized by the formation of a dense annular plasma shell, the sheath, that is driven to the axis by magnetic forces and therefore subject to the magneto-Rayleigh–Taylor instability. Here, the conditions within these sheaths are measured on the 1-MA COBRA generator at Cornell University [Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)] for various gas species and initial fill densities. The gas-puff loads are initialized by a 7 cm diameter triple-nozzle gas valve assembly with concentric outer and inner annular nozzles and a central gas jet. Thomson scattering and laser interferometry provide spatially resolved flow, temperature, and electron density profiles midway through the implosion, while extreme ultraviolet pinhole cameras record the evolution of the plasma column and photoconducting diodes measure x-ray emission. Analysis of the scattering spectra includes a means of discriminating between thermal and non-thermal broadening to test for the presence of hydrodynamic turbulence. Two types of sheath profiles are observed, those with sharp discontinuities at the leading edge and those with smooth gradients. In both cases, non-thermal broadening is generally peaked at the front of the sheath and exhibits a characteristic decay length that roughly scales with the sheath ion mean free path. We demonstrate that this non-thermal broadening term is inconsistent with laminar velocity gradients and is more consistent with dissipative turbulence driven by unstable plasma waves in a collisionless shock. The resulting differences in sheath profile are then set by the sheath ion collisionality in a manner consistent with recent 1D kinetic simulations [Angus et al., Phys. Plasmas 28, 010701 (2021)].

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8

Stenzel, Reiner L., Johannes Grünwald, Codrina Ionita, Roman Schrittwieser, and Manuel Urrutia. "Sheaths and Double Layers with Instabilities." Journal of Technological and Space Plasmas 2, no. 1 (March 24, 2021): 70–92. http://dx.doi.org/10.31281/jtsp.v2i1.16.

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The properties of sheaths and associated potential structures and instabilities cover a broad field which even a review cannot cover everything. Thus, the focus will be on about a dozen examples, describe their observations and focus on the basic physical explanations for the effects, while further details are found in the references. Due to familiarity the review focuses mainly on the authors work but compared and referenced related work. The topics start with a high frequency oscillations near the electron plasma frequency. Low frequency instabilities also occur at the ion plasma frequency.The injection of ions into an electron-rich sheath widens the sheath and forms a double layer. Likewise, the injection of electrons into an ion rich sheath widens and establishes a double layer which occurs in free plasma injection into vacuum. The sheath widens and forms a double layer by ionization in an electron rich sheath. When particle fluxes in "fireballs" gets out of balance the double layer performs relaxation instabilities which has been studied extensively. Fireballs inside spherical electrodes create a new instability due to the transit time of trapped electrons. On cylindrical and spherical electrodes the electron rich sheath rotates in magnetized plasmas. Electrons rotate due to $\mathbf E \times \mathbf B_0$ which excites electron drift waves with azimuthal eigenmodes. Conversely a permanent magnetic dipole has been used as a negative electrode. The impact of energetic ions produces secondary electron emission, forming a ring of plasma around the magnetic equator. Such "magnetrons" are subject to various instabilities. Finally, the current to a positively biased electrode in a uniformly magnetized plasma is unstable to relaxation oscillations, which shows an example of global effects. The sheath at the electrode raises the potential in the flux tube of the electrode thereby creating a radial sheath which moves unmagnetized ions radially. The ion motion creates a density perturbation which affects the electrode current. If the electrode draws large currents the current disruptions create large inductive voltages on the electrode, which again produce double layers. This phenomenon has been seen in reconnection currents. Many examples of sheath properties will be explained. Although the focus is on the physics some examples of applications will be suggested such as neutral gas heating and accelerating, sputtering of plasma magnetrons and rf oscillators.

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9

Ghomi, Hamid, Mansour Khoramabadi, Padma Kant Shukla, and Mahmod Ghorannevis. "Plasma sheath criterion in thermal electronegative plasmas." Journal of Applied Physics 108, no. 6 (September 15, 2010): 063302. http://dx.doi.org/10.1063/1.3475508.

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10

Yang, Xiaocui, Kai Yuan, Yuhao Wang, and Mingyang Mao. "Numerical modeling on the bit error rate of EHF communication in time-varying hypersonic plasma sheath." AIP Advances 12, no. 4 (April 1, 2022): 045318. http://dx.doi.org/10.1063/5.0087974.

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Plasma sheaths enveloping hypersonic vehicles could yield a communication blackout. Many previous studies have shown that the electromagnetic wave in an extremely high frequency (EHF) band could penetrate a hypersonic plasma sheath effectively. In other words, the EHF communication could be a potential solution to the communication blackout problem. Nevertheless, most of those works used to concern only the EHF signal attenuation. In addition, those works normally treated plasma sheaths as a static plasma layer. However, plasma sheaths always keep evolving. In the present study, the modulated EHF signal propagation in a time-varying plasma sheath was investigated numerically. The plasma sheath was obtained with a hypersonic hydrodynamical model that has been utilized in previous studies. The EHF signal propagation was modeled based on theories of geometrical optics. The frequencies studied are 94, 140, and 225 GHz. The investigation revealed that not only signal attenuation but also the phase shifts for carrier waves vary with time. Their impact on the bit error rate (BER) of the EHF communication system was studied numerically. The modulation modes concerned in the present study are 2ASK, 2PSK, 4QAM, and Non-Coherent demodulation 2FSK (NC-2FSK). According to the study, the BER keeps varying with time. This study also showed that the BER is impacted by the carrier frequency, modulation mode, and the demodulation method. According to the comparison and the analysis, the suggested modulation modes are 2PSK and 4QAM at the carrier frequency of 140 GHz, which could lead to smaller and more stable BER for the EHF communication system utilized by hypersonic vehicles.

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11

UHM, HAN S. "Reduction of sheath electric field by multidielectric slabs in a plasma." Journal of Plasma Physics 63, no. 2 (February 2000): 129–37. http://dx.doi.org/10.1017/s0022377899008144.

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The properties of plasma sheaths developed along plasma boundaries are investigated analytically, assuming that dielectric slabs are present between electrodes. A collisionless plasma is confined by two planar electrodes. Planar dielectric slabs with finite thickness partition the plasma into many pieces. The sheath electric field is inversely proportional to the sum of 2(1+l)+Δ/ελ, where Δ and ε are the total thickness and the relative dielectric constant respectively of the dielectric slabs, l is the number of slabs and λ is the Debye length of the high-density plasma. In this context, the plasma sheaths may easily be controlled by appropriate choices of dielectric materials and their size.

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12

Sheridan, T. E., and J. Goree. "Collisional plasma sheath model." Physics of Fluids B: Plasma Physics 3, no. 10 (October 1991): 2796–804. http://dx.doi.org/10.1063/1.859987.

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13

Mun, J.-H., M. Muraglia, O. Agullo, C. Arnas, and L. Couedel. "Ion temperature profile importance in collisional sheath modelling." Journal of Physics: Conference Series 2397, no. 1 (December 1, 2022): 012016. http://dx.doi.org/10.1088/1742-6596/2397/1/012016.

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Abstract A plasma fluid model is being developed for the simulation of a direct current plasma discharge simulation including the sheath regions. The code uses a second order centered finite difference scheme and time integration is done by strong stability preserving third order Runge-Kutta method. The separation of scalar and vectorial quantities in two different grids gives stable results. After validation by comparison with theoretical ion sheath profiles, a one dimensional direct current argon discharge was simulated and compared to 1D3v particle-in-cell simulation results. It is shown that the inclusion of a non constant ion temperature profile is mandatory in fluid models in order to recover correct increase of ion velocity in sheaths and thus to simulate direct current (DC) discharges where collisions are not negligible in the sheaths.

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14

Ivchenko, N., L. Facciolo, P. A. Lindqvist, P. Kekkonen, and B. Holback. "Disturbance of plasma environment in the vicinity of the Astrid-2 microsatellite." Annales Geophysicae 19, no. 6 (June 30, 2001): 655–66. http://dx.doi.org/10.5194/angeo-19-655-2001.

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Abstract. The presence of a satellite disturbs the ambient plasma. The charging of the spacecraft creates a sheath around it, and the motion of the satellite creates a wake disturbance. This modification of the plasma environment introduces difficulties in measuring electric fields and plasma densities using the probe technique. We present a study of the structure of the sheath and wake around the Astrid-2 microsatellite, as observed by the probes of the EMMA and LINDA instruments. Measurements with biased LINDA probes, as well as current sweeps on the EMMA probes, show a density enhancement upstream of the satellite and a plasma depletion behind the satellite. The electric field probes detect disturbances in the plasma potential on magnetic field lines connected to the satellite.Key words. Space plasma physics (spacecraft sheaths, wakes, charging; instruments and techniques)

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15

Yang, Min, Haojie Zhang, Xiaoping Li, Qianqian Sun, and Jiancheng Tang. "The PSK Channel Capacity Estimation under Dynamic Plasma Sheath Channel." International Journal of Antennas and Propagation 2020 (April 9, 2020): 1–9. http://dx.doi.org/10.1155/2020/3652429.

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During the reentry process, the plasma sheath covering the surface of the hypersonic aircraft will cause the amplitude attenuation and phase jitter of the communication electromagnetic waves. Channel parameters such as the electron density and collision frequency of the plasma sheath reflect the changing trend of the plasma sheath, and these parameters can be measured by physical means. However, these parameters cannot directly reflect the change of the channel communication ability and cannot directly serve the design of communication methods in the plasma sheath. Due to the particularity of the plasma sheath, the traditional channel estimation method for Additive White Gaussian Noise channels will no longer be applicable. This paper presents a channel capacity estimation method for dynamic plasma sheath. First, the plasma sheath is equivalent to a discrete input continuous output memoryless channel, and then the channel capacity expression is derived according to Shannon formula. Finally, the channel capacity of the dynamic plasma sheath is estimated by calculating the transition probability density function. The simulation results show that the channel capacity of the dynamic plasma sheath is affected by both the signal-to-noise ratio (SNR) and the dynamic parameters of the plasma sheath. When the electron density is small, the channel capacity is mainly affected by the SNR. As the electron density increases, the dynamic parameters of the plasma sheath gradually become the main factor affecting the channel capacity. This method is a theoretical analysis of the channel capacity when the channel parameters of the plasma channel are known, and it is meaningful for conducting the work of communication methods design.

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16

ZHANG, Qifan, Yiping HAN, Qinlu DONG, and Chang DONG. "Analysis of the influence of sheath positions, flight parameters and incident wave parameters on the wave propagation in plasma sheath." Plasma Science and Technology 24, no. 3 (March 1, 2022): 035003. http://dx.doi.org/10.1088/2058-6272/ac2e53.

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Abstract The plasma sheath covering hypersonic vehicles has a significant effect on the propagation of electromagnetic waves. Based on the calculation of the flow field of a conical cylindrical, this work studies the propagation of electromagnetic waves in plasma sheath at L-band and Ku-band, and discusses the propagation characteristics in the head, side and tail of the sheath. The dielectric properties of plasma sheath are related to flight speed and altitude. A flight condition corresponds to a unique distribution of dielectric properties. For the conical cylindrical, the results show that flight speed is generally negatively correlated with the transmissivity of the plasma sheath. The reflection characteristics of electromagnetic waves at the L-band and Ku-band when obliquely incident to the plasma sheath show a downward trend. When the frequency is increased to Ku-band, the propagation characteristics of electromagnetic waves in the plasma sheath are related to the position of the sheath.

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17

GHOMI, HAMID, and MANSOUR KHORAMABADI. "Influence of ion temperature on plasma sheath transition." Journal of Plasma Physics 76, no. 2 (October 13, 2009): 247–55. http://dx.doi.org/10.1017/s0022377809990304.

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AbstractUsing a two-fluid model, the ion transition from plasma sheath boundary is investigated taking into account the effect of the finite ion temperature. It is shown that by considering the effects of neutral-ion elastic collision on the sheath, there will be an upper as well as a lower limit for the ion transition velocity into the sheath. The dependency of upper and lower limits of the ion transition velocity on the ion temperature is investigated, and it is shown that the finite ion temperature only affects lower limits in non-hot plasmas.

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18

Czarnetzki, U., D. Luggenhölscher, V. A. Kadetov, and H. F. Döbele. "Plasma diagnostics by laser spectroscopic electric field measurement." Pure and Applied Chemistry 77, no. 2 (January 1, 2005): 345–58. http://dx.doi.org/10.1351/pac200577020345.

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Laser spectroscopic electric field measurements have the potential to become a versatile tool for the diagnostics of low-temperature plasmas. From the spatially and temporally resolved field distribution in the sheath close to electrodes or surfaces in general, a broad range of important plasma parameters can be inferred directly: electron temperature; ion density distribution; displacement-, ion-, electron-diffusion current density; and the sheath potential. Indirectly, the electron and ion energy distribution functions and information on the ion dynamics in the sheath can also be obtained. Finally, measurements in the quasi-neutral bulk can also reveal even the plasma density distribution with high spatial and temporal resolution. The basic concepts for analysis of the field data are introduced and demonstrated by examples in hydrogen discharges.

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Yu, Pengcheng, Yu Liu, Xiangqun Liu, and Jiuhou Lei. "Sheath expansion effect of double flush mounted probe in weakly ionized plasma." Physics of Plasmas 29, no. 9 (September 2022): 093508. http://dx.doi.org/10.1063/5.0099065.

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Sheath expansion is a distinctive feature of the double flush mounted probe because of the embedded configuration. Previously, the sheath expansion effect was usually neglected in weakly ionized plasma dominated by collisions between charged particles and neutrals. In this work, we investigated the sheath expansion effect of the double flush mounted probe in weakly ionized plasma. Results indicate that measurements using the double flush mounted probe were also influenced to a certain extent by the sheath expansion effect in weakly ionized plasma. To eliminate the influence, an empirical analytical formula has been presented to eliminate the influence of sheath expansion. In addition, a fitting curve is given based on experimental data, which indicates that sheath expansion should be considered in processing the measured data when the plasma pressure is lower than 200 Pa. In summary, this work indicates that the ion–neutral collision is a crucial factor that affects sheath expansion in addition to the radius parameter and probes' bias, which can be extended to double flush mounted probe diagnostics in collisional plasma such as the reentry plasma sheath and high-powered plasma thruster.

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20

Pannese, Ennio. "The structure of the perineuronal sheath of satellite glial cells (SGCs) in sensory ganglia." Neuron Glia Biology 6, no. 1 (February 2010): 3–10. http://dx.doi.org/10.1017/s1740925x10000037.

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In sensory ganglia each nerve cell body is usually enveloped by a satellite glial cell (SGC) sheath, sharply separated from sheaths encircling adjacent neurons by connective tissue. However, following axon injury SGCs may form bridges connecting previously separate perineuronal sheaths. Each sheath consists of one or several layers of cells that overlap in a more or less complex fashion; sometimes SGCs form a perineuronal myelin sheath. SGCs are flattened mononucleate cells containing the usual cell organelles. Several ion channels, receptors and adhesion molecules have been identified in these cells. SGCs of the same sheath are usually linked by adherent and gap junctions, and are functionally coupled. Following axon injury, both the number of gap junctions and the coupling of SGCs increase markedly. The apposed plasma membranes of adjacent cells are separated by 15–20 nm gaps, which form a potential pathway, usually long and tortuous, between connective tissue and neuronal surface. The boundary between neuron and SGC sheath is usually complicated, mainly by many projections arising from the neuron. The outer surface of the SGC sheath is covered by a basal lamina. The number of SGCs enveloping a nerve cell body is proportional to the cell body volume; the volume of the SGC sheath is proportional to the volume and surface area of the nerve cell body. In old animals, both the number of SGCs and the mean volume of the SGC sheaths are significantly lower than in young adults. Furthermore, extensive portions of the neuronal surface are not covered by SGCs, exposing neurons of aged animals to damage by harmful substances.

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Riemann, K.-U., J. Seebacher, D. D. Tskhakaya, and S. Kuhn. "The plasma–sheath matching problem." Plasma Physics and Controlled Fusion 47, no. 11 (October 14, 2005): 1949–70. http://dx.doi.org/10.1088/0741-3335/47/11/006.

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Hrach, Rudolf, Věra Hrachová, and Miroslav Vicher. "Sheath evolution in electronegative plasma." Computer Physics Communications 147, no. 1-2 (August 2002): 505–8. http://dx.doi.org/10.1016/s0010-4655(02)00355-7.

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23

Franklin, R. N. "The plasma–sheath boundary region." Journal of Physics D: Applied Physics 36, no. 22 (October 30, 2003): R309—R320. http://dx.doi.org/10.1088/0022-3727/36/22/r01.

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24

Ignatov, A. M., P. P. J. M. Schram, and S. A. Trigger. "Surface Tension of Plasma Sheath." Contributions to Plasma Physics 45, no. 3-4 (July 2005): 192–97. http://dx.doi.org/10.1002/ctpp.200510020.

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Clements, R. M., J. R. Dawe, S. A. H. Rizvi, and P. R. Smy. "Measurement of sheath characteristics in the presence of convection and ionization." Canadian Journal of Physics 74, no. 9-10 (September 1, 1996): 671–75. http://dx.doi.org/10.1139/p96-096.

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A flame plasma whose electron and (or) ion density can be varied over several orders of magnitude is constrained to flow perpendicular to a planar grid Langmuir probe. The probe is biased negative to the plasma, and the current–voltage characteristics and the thickness of the ion sheath formed at the probe are measured. The level of the electron and (or) ion density is set within a range at which the probe current due to thermal ionization throughout the sheath is comparable with the current of ions convected into the sheath. The experimental results are compared with the predictions of a recent theoretical paper that calculates the effect of recombination upon the characteristics of planar, cylindrical, and spherical probes with boundary layer sheaths. The theoretical predictions and experimental results for an idealized planar configuration show good agreement over wide ranges of variation of probe bias and plasma electron and (or) ion density. This verification of the theoretical planar electrode – perpendicular-flow model, which is the basis for all three boundary layer relations, is seen as providing strong backing for these relations, which have application to ionization measurements in various forms of recombinant plasma.

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Song, Lihao, Bowen Bai, Xiaoping Li, Gezhao Niu, Yanming Liu, Liang Zhao, and Hui Zhou. "Analysis of Hypersonic Platform-Borne SAR Imaging: A Physical Perspective." Remote Sensing 13, no. 23 (December 5, 2021): 4943. http://dx.doi.org/10.3390/rs13234943.

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The usage of a hypersonic platform for remote sensing application has promising prospects, especially for hypersonic platform-borne synthetic aperture radar (SAR) imaging. However, the high-speed of hypersonic platform will lead to extreme friction between the platform and air, which will cause the ionization of air. The ionized gas forms the plasma sheath wrapped around the hypersonic platform. The plasma sheath will severely affect the propagation of SAR signal and further affect the SAR imaging. Therefore, hypersonic platform-borne SAR imaging should be studied from a physical perspective. In this paper, hypersonic platform-borne SAR imaging under plasma sheath is analyzed. The SAR signal propagation in plasma sheath is computed using scatter matrix method. The proposed SAR signal model is verified by using a ground experiment system. Moreover, the effect of attenuation caused by plasma sheath on SAR imaging is studied under different SAR parameters and plasma sheath. The result shows that attenuation caused by plasma sheath will degrade the SAR imaging quality and even cause the point and area targets to be submerged into the noise. The real SAR images under plasma sheath also illustrate this phenomenon. Furthermore, by studying imaging results under different SAR and plasma parameters, it can be concluded that the severe degradation of SAR imaging quality appears at condition of high plasma sheath electron density and low SAR carrier frequency. The work in this paper will be beneficial for the study of hypersonic platform-borne SAR imaging and design of hypersonic SAR imaging systems in the future.

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Ewart, Robert J., Felix I Parra, and Alessandro Geraldini. "Sheath collapse at critical shallow angle due to kinetic effects." Plasma Physics and Controlled Fusion 64, no. 1 (December 6, 2021): 015010. http://dx.doi.org/10.1088/1361-6587/ac3966.

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Abstract The Debye sheath is known to vanish completely in magnetised plasmas for a sufficiently small electron gyroradius and small angle between the magnetic field and the wall. This angle depends on the current onto the wall. When the Debye sheath vanishes, there is still a potential drop between the wall and the plasma across the magnetic presheath. The magnetic field angle corresponding to the predicted sheath collapse is shown to be much smaller than previous estimates, scaling with the electron-ion mass ratio and not with the square root of the mass ratio. This is shown to be a consequence of the kinetic electron and finite ion orbit width effects, which are not captured by fluid models. The wall potential with respect to the bulk plasma at which the Debye sheath vanishes is calculated. Above this wall potential, it is possible that the Debye sheath will invert.

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Tang, Xian-Zhu, and Zehua Guo. "Sheath energy transmission in a collisional plasma with collisionless sheath." Physics of Plasmas 22, no. 10 (October 2015): 100703. http://dx.doi.org/10.1063/1.4933415.

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Din, Alif. "Plasma sheath in the presence of surface-emitted negative ions." Physics of Plasmas 29, no. 12 (December 2022): 123507. http://dx.doi.org/10.1063/5.0112937.

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The need for negative hydrogen ion sources for heating in future fusion devices demands a full investigation of its production and interaction with plasma. To understand the interaction of emitted negative ions with plasma sheath, a one-dimensional collisionless kinetic model of a negative ion emitting electrode/grid in a low-density isotropic plasma is developed for conventional and the inverse sheath. The plasma electron and emitted negative ions are assumed to be half Maxwellian along with cold positive plasma ions for the conventional sheath and half Maxwellian for the inverse sheath. The influence of surface-produced negative ions, from floating and current-carrying electrode/grid, with varying temperatures on sheath structures, is analyzed for subcritical, critical, and supercritical emissions. The formation of potential well and inverse sheath is observed at high and very high emitted negative ion temperatures, respectively. The critical emission is observed at specific values of emitted negative ion temperature and number density, below which the solution does not exists. In critical and supercritical emission, the emitted negative ion number density remains low compared with plasma positive ions, but it is high in inverse sheath. The inverse sheath solutions for floating and current-carrying negative ion-emitting electrode/grid are also discussed, and a rough estimation between the experiment and this theory shows the existence of inverse sheath in currently existing negative ion sources, but for full understanding, we need further investigations.

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Allam, Tarek M., Hanaa A. El-Sayed, and Hanaa M. Soliman. "Plasma Current Sheath Motion in Coaxial Plasma Discharge." Energy and Power Engineering 03, no. 04 (2011): 436–43. http://dx.doi.org/10.4236/epe.2011.34054.

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31

Xin Xin Wang and Tsin Chi Yang. "Effect of plasma sheath structure in plasma focus." IEEE Transactions on Plasma Science 21, no. 1 (1993): 175–80. http://dx.doi.org/10.1109/27.221118.

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32

Jia, Long, and Hong Guang Ma. "Study of the Attenuation Characteristic of Electromagnetic Waves in Plasma Sheath." Advanced Materials Research 1044-1045 (October 2014): 104–10. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.104.

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Plasma sheath that seriously impacts the propagation of electromagnetic waves will be produced when an aircraft flying in the atmosphere at very high speed. This thesis concentrates on the study of the attenuation characteristic of electromagnetic waves in plasma sheath. Through discussing the formation mechanism of plasma sheath and analyzing the propagation characteristic of electromagnetic waves, the scope of communication outage will be learned. The plasma sheath is segmented into plentiful subshells which are considered as uniform layers. Ultimately the factors which affect the attenuation of electromagnetic waves will be known.

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George, A., T. Kalvas, S. Melanson, M. Dehnel, and N. G. R. Broderick. "H^- beam emittance analysis in a multicusp ion source." Journal of Physics: Conference Series 2244, no. 1 (April 1, 2022): 012038. http://dx.doi.org/10.1088/1742-6596/2244/1/012038.

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Abstract Emittance of the ion beam extracted from an ion source is dependent on the initial focusing action at the plasma sheath. The properties of the plasma sheath is further dependent on the local electric fields and charge densities around the sheath. Experiments are conducted for creating different sets of conditions around the plasma sheath in an H- multicusp filament ion source and the resulting emittance of the extracted H- ion beam is measured. Variation of beam emittance under different plasma densities, electrode voltages and gas flows are analysed.

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Kaphle, Vikash, and Raju Khanal. "Sheath Structure in Oxygen Plasma for Different Presheath Plasma Density." Himalayan Physics 1 (July 27, 2011): 10–13. http://dx.doi.org/10.3126/hj.v1i0.5164.

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Zinc oxide films are used as transparent conductive electrode for preparing organic light-emitting devices. In plasma-enhanced vapor deposition oxygen plasma is formed which then react with zinc atoms forming zinc oxide plasma, which is then deposited to the substrate. Hence, the proper understanding of the oxygen plasma-wall interaction is of crucial importance because of its application in plasma depositions. We have studied the sheath structure in oxygen plasma formed in front of an absorbing material wall for different density at the presheath side. We have used a kinetic trajectory simulation model to simulate the oxygen plasma. It has been observed that the sheath structure is highly affected by the plasma density at the presheath side. Hence, the densities of particles reaching the wall can be controlled by adjusting the presheath plasma density which is the key to thin film deposition.Keywords: Plasma; Sheath; Presheath; Quasineutrality; Bohm criterionThe Himalayan Physics Vol.1, No.1, May, 2010Page: 10-13Uploaded Date: 28 July, 2011

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Barnwal, Prashant K., A. Ganguli, R. Narayanan, and R. D. Tarey. "Effect of plasma boundary and electrode asymmetry in planar DC discharge system." Physics of Plasmas 29, no. 7 (July 2022): 072102. http://dx.doi.org/10.1063/5.0091108.

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This paper present presents a detailed characterization and analysis of plasma formation using different anode sizes in two contrasting configurations in a planar DC discharge system. One configuration has a conducting boundary (CB) formed by the conducting wall of the vacuum chamber that acts as an extended cathode. The second configuration, the Small Volume Insulated Boundary (SVIB) with a volume 22.5 times smaller than the CB system, is realized by confining the plasma completely within a fully insulating boundary. Anode sizes may be equal to the cathode size (symmetric electrodes) or smaller (asymmetric electrodes). In general, CB discharges require much lower applied voltages, showing very little variation with the pressure. Although the s ymmetric CB discharges have only single electron population, the asymmetric electrode discharges exhibit two electron populations, a high-density bulk population ( Te ∼ 2–3 eV) and a very low-density warm population ( Tw ∼ 40 eV) that serves to enhance ionization and compensate for reduced anode size. In contrast, the SVIB discharges require high voltages, show considerable variation in discharge voltage both with pressure and anode size, and have higher densities. In addition, one finds two electron populations for all anode sizes. From estimates of the anode sheath drop, it is possible to show that all CB discharges have an electron-rich anode sheath for all anode sizes. In contrast, the SVIB discharges exhibit ion-rich anode sheaths for all anode sizes, although for small-sized anodes and high pressures the sheaths transform to an electron-rich sheath.

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Sahu, Rupali, Albina Tropina, and Richard Miles. "Isentropic plasma sheath model for improved fidelity." Physics of Plasmas 29, no. 4 (April 2022): 040701. http://dx.doi.org/10.1063/5.0084712.

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A model is developed for a collisionless plasma sheath assuming isentropic electrons in contrast to the standard isothermal electron assumption. This approach is enabled by the approximation of a Maxwellian electron velocity distribution function across the sheath, which is justified by near wall measurements. The conservation of entropy leads to a modified Boltzmann relation and a modified Bohm criterion. The predicted floating sheath potential is in excellent agreement with experimental data. Takamura's model for a space-charge limited plasma sheath near an emissive surface is also modified for isentropic electrons and with that modification agrees well with numerical results from a full fluid plasma model.

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KALITA, P., and G. C. DAS. "Characteristic behaviour of dust grains in a sheath formed in plasma with negative ions." Journal of Plasma Physics 69, no. 6 (November 25, 2003): 551–63. http://dx.doi.org/10.1017/s0022377803002277.

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The motivation of this paper is to study the formation of a sheath in plasma contaminated with additional negative ions. Sheath formation has been analysed through the solution of the Sagdeev potential equation derived in a plasma by using the pseudopotential method. Because of the negative ions, it has been shown that the sheath formation, in contrast to that in a simple plasma, faces difficulties. A potential barrier from which modes are reflected is introduced and the potential variation beyond it is complex which, in turn, shows new findings. It is also revealed that the potential variation should be estimated in the plasma sheath in the presence of low as well as high negative-ion concentrations. The levitation of a dust grain into the sheath and its characteristic behaviour have also been investigated. Furthermore, the dust size in the ideal plasma sheath along with the causes of formation of the dust atmosphere have been studied.

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Oksuz, L., and N. Hershkowitz. "Plasma, presheath, collisional sheath and collisionless sheath potential profiles in weakly ionized, weakly collisional plasma." Plasma Sources Science and Technology 14, no. 1 (February 1, 2005): 201–8. http://dx.doi.org/10.1088/0963-0252/14/1/022.

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Chen, Yuqing, Lei Wang, Lishan Zhao, Junpu Ling, Xingjun Ge, and Juntao He. "Simulation study of alleviating the communication blackout using high-power microwave irradiating plasma sheaths." Physics of Plasmas 29, no. 12 (December 2022): 123505. http://dx.doi.org/10.1063/5.0105947.

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During hypersonic vehicle flight at high speed, plasma sheath on the vehicle surface will attenuate or even interrupt the communication signal, leading to the “communication blackout” problem. The vehicle probably moves a long distance during the communication blackout due to its high speed, which is a serious threat to the safety of the vehicle. This paper proposes a method to solve the communication blackout problem using high-power microwave (HPM) irradiation. The multicomponent compressible model, finite difference time domain algorithm, and multi-fluid model are used to simulate the interaction between HPM and plasma sheath. The results show that after HPM irradiation, the electromagnetic (EM) wave transmissivity of the plasma sheath will change, and the electric field (E-field) amplitude and irradiation time of HPM significantly influence the change of transmissivity. Thereafter, analyses of the changes of the collision and plasma frequencies of the plasma sheath after HPM irradiation showed the transmissivity of the plasma sheath to low-frequency EM waves is improved by optimizing E-field amplitude and irradiation time of HPM. Therefore, HPM irradiation can be performed to enhance the transmissivity of the plasma sheath to the communication signal, thus alleviating the communication blackout problem.

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Dahal, Prem, Roshan Chalise, and Raju Khanal. "Effect of Permittivity of Plasma Medium on the Particle Properties and Electric Field in a Magnetized Plasma Sheath." Amrit Research Journal 3, no. 01 (December 23, 2022): 101–8. http://dx.doi.org/10.3126/arj.v3i01.50505.

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The plasma sheath, a thin layer having sharp gradients, is necessary to be formed at any material wall in exposure with plasma for its stability. Characteristics of magnetized plasma sheath formed in front of a material wall for different permittivity of plasma medium has been studies using the kinetic trajectory simulation (KTS) model. The electron density, ion density, electric field and potential decreases on moving away from the sheath entrance but total charge density increases. As plasma is composed of charged particles, any variation in the permittivity of the medium has significant effects on the sheath properties. It is found that on increasing the permittivity of the medium, the electric potential strength and hence electric field decreases because of increased shielding ability of the plasma. The results are in qualitative agreement with earlier studies based on the fluid approach but the kinetic approach is more accurate quantitatively providing a better perception of plasma-wall transition phenomena.

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Liu, Jiang Fan, Guo Bin Wan, Jin Sheng Zhang, and Xiao Li Xi. "Analysis of the Impact of Plasma Sheath on GPS Antenna." Applied Mechanics and Materials 229-231 (November 2012): 1614–17. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.1614.

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The electromagnetic simulation software CST was used to analyze the effects of reentry plasma sheath on the GPS navigation antenna. The Impedance and radiation characteristics of antenna were studied on condition that the antenna was coated with uniform and nonuniform electron density distribution plasma sheath respectively. The results show that, the antenna coated with the uniform plasma sheath, the plasma electron density increasing, the antenna operating frequency moves to high-frequency and that the directivity decreases as well; when the antenna was coated with nonuniform plasma, with the higher electron peak density of plasma sheath, besides that the operating frequency also moves to high-frequency, the bandwidth stretches wide and the return loss reduces; the antenna radiation pattern distorts seriously at the electron peak density of 1018m-3.

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Stenzel, R. L., J. Gruenwald, C. Ionita, and R. Schrittwieser. "Electron-rich sheath dynamics. I. Transient currents and sheath-plasma instabilities." Physics of Plasmas 18, no. 6 (June 2011): 062112. http://dx.doi.org/10.1063/1.3601858.

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Zhao, Liang, Wei Min Bao, and Chun Ye Gong. "An Overview of the Research of Plasma Sheath." Advanced Materials Research 1049-1050 (October 2014): 1518–21. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.1518.

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The plasma sheath can be regarded as a model of a phenomenon of spacecraft reentry or hypersonic vehicles and causes so called radio blackout, which interferes with radio signals. This paper gives a survey on several aspects of plasma sheath, including the characteristic of plasma sheath, experiments to deal with the blackout and numerical solutions. The numerical methods includes WKB, finite-difference time-domain method, particle-in-cell method, CFD based method and Monte Carlo method. Some discussions are also presented.

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Seng, Y. S., P. Lee, and R. S. Rawat. "Current sheath formation in the plasma focus." International Journal of Modern Physics: Conference Series 32 (January 2014): 1460321. http://dx.doi.org/10.1142/s2010194514603214.

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The shaping and formation of the current sheath takes place in the breakdown phase of a plasma focus device. Achieving a clear understanding of the current sheath formation process is important because the plasma focus device performance depends on the quality of this sheath. In this paper, we created and successfully run an electromagnetic particle in cell code to simulate the breakdown phase. Magnetic effects are self-consistently incorporated in this formalism, allowing us to carry the simulation all the way to the point prior to breakdown.

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Zhao, Ziyang, Bo Bai, Kai Yuan, Rongxin Tang, Jiawei Xiong, and Kaili Wang. "Effect of Terahertz Antenna Radiation in Hypersonic Plasma Sheaths with Different Vehicle Shapes." Applied Sciences 12, no. 4 (February 10, 2022): 1811. http://dx.doi.org/10.3390/app12041811.

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Communication blackout caused by the plasma sheath surrounding hypersonic vehicles is a serious threat to the safety of hypersonic vehicles. Terahertz (THz) communication is considered to be a potential solution to the blackout problem. However, hypersonic plasma sheaths can affect not only electromagnetic wave propagation, but also the radiation performance of onboard antennae. Therefore, it is necessary to investigate the radiation performance of THz antennae in hypersonic plasma sheaths. In the present study, the impact of vehicle shapes (blunt-coned and sharp-coned vehicles) on plasma sheaths was investigated numerically. The antenna involved in the present study was a 0.14 THz array antenna. The antenna performance was compared with the aspects of mainlobe gain, mainlobe direction, and mainlobe width. The present study shows that both sharp-coned and blunt-coned plasma sheaths are inhomogeneous. Nevertheless, their structures are obviously different. Such differences yield different antenna performance in sharp-coned and blunt-coned plasma sheaths. Compared with sharp-coned plasma sheaths, blunt-coned plasma sheaths can refract antenna radiation direction, which can result in worsened communication quality in the expected direction. In addition, the phenomena are discussed in detail. Suggestions of vehicle shape design to guarantee communication quality in hypersonic flight missions are proposed.

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Zou Xiu, Liu Jin-Yuan, Wang Zheng-Xiong, Gong Ye, Liu Yue, and Wang Xiao-Gang. "Plasma sheath in a magnetic field." Acta Physica Sinica 53, no. 10 (2004): 3409. http://dx.doi.org/10.7498/aps.53.3409.

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Carter, M. D., D. B. Batchelor, and E. F. Jaeger. "Electromotive excitation of a plasma sheath." Physics of Fluids B: Plasma Physics 4, no. 5 (May 1992): 1081–91. http://dx.doi.org/10.1063/1.860466.

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Holland, D. L., B. D. Fried, and G. J. Morales. "Sheath structure in a magnetized plasma." Physics of Fluids B: Plasma Physics 5, no. 6 (June 1993): 1723–37. http://dx.doi.org/10.1063/1.860806.

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Badsi, Mehdi, Michel Mehrenberger, and Laurent Navoret. "Numerical stability of a plasma sheath." ESAIM: Proceedings and Surveys 64 (2018): 17–36. http://dx.doi.org/10.1051/proc/201864017.

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We are interested in developing a numerical method for capturing stationary sheaths, that a plasma forms in contact with a metallic wall. This work is based on a bi-species (ion/electron) Vlasov-Ampère model proposed in [3]. The main question addressed in this work is to know how accurately classical time-dependent Vlasov-Ampère numerical schemes preserve in long time these non-homogeneous stationary solutions with emission/absorption boundary conditions. In the context of high-order semi-Lagrangian methods, due to their large stencil, interpolation near the boundary of the domain requires also a specific treatment.

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Wei-dong, Huang, Hu Min, and Zhan Ru-juan. "Sheath Characteristic in ECR Plasma Nitriding." Plasma Science and Technology 3, no. 2 (April 2001): 727–32. http://dx.doi.org/10.1088/1009-0630/3/2/009.

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