Ion-neutral collision effect on ion-ion two-stream-instability near sheath-presheath boundary in two-ion-species plasmas

Kim, Nam Kyun; Song, Ju Sun; Roh, Hyun-Joon; Jang, Yongwon; Ryu, Sangwon; Huh, Sung-Ryul; Kim, Gon−Ho

doi:10.1088/1361-6595/aa67c4

Cited by 12 publications

(18 citation statements)

References 21 publications

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“…2; thus, the gap initially contains only neutrals. The goal of this geometry is to explore plasmas with relative drift (as in strongly coupled beams [67,68]), fluid instabilities (such as Kelvin-Helmholtz [69,70] and Rayleigh-Taylor [71] instabilities), two-stream [72][73][74] and bump-on-tail [75] instabilities, and stopping-power [76][77][78] geometries. The geometry of the gapped-slab SUNP studied here is shown in Fig.…”

Section: Gapped-slab Sunp: Beam Formationmentioning

confidence: 99%

Sculpted ultracold neutral plasmas

Dharodi

Murillo

2020

Phys. Rev. E

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Ultracold neutral plasma (UNP) experiments allow for careful control of plasma properties across Coulomb coupling regimes. Here, we examine how UNPs can be used to study heterogeneous, nonequilibrium phenomena, including nonlinear waves, transport, hydrodynamics, kinetics, stopping power, and instabilities. Through a series of molecular dynamics simulations, we have explored UNPs formed with spatially modulated ionizing radiation. We have developed a computational model for such sculpted UNPs that includes an ionic screened Coulomb interaction with a spatiotemporal screening length, and Langevin-based spatial ion-electron and ion-neutral collisions. We have also developed a hydrodynamics model and have extracted its field quantities (density, flow velocity, and temperature) from the molecular dynamics simulation data, allowing us to investigate kinetics by examining moment ratios and phase-space dynamics; we find that it is possible to create UNPs that vary from nearly perfect fluids (Euler limit) to highly kinetic plasmas. We have examined plasmas in three geometries: a solid rod, a hollow rod, and a gapped slab; we have studied basic properties of these plasmas, including the spatial Coulomb coupling parameter. By varying the initial conditions, we find that we can design experimental plasmas that would allow the exploration of a wide range of phenomena, including shock and blast waves, stopping power, two-stream instabilities, and much more. Using an evaporative cooling geometry, our results suggest that much larger Coulomb couplings can be achieved, possibly in excess of 10.

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Section: Gapped-slab Sunp: Beam Formationmentioning

confidence: 99%

Sculpted ultracold neutral plasmas

Dharodi

Murillo

2020

Phys. Rev. E

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“…LIF was thus established to be the better diagnostics for IVDFs/NVDFs and were widely used as a tool to measure ion flow [4], ion temperature [5], magnetic field strength [6], and ion density [7]. It is becoming an increasingly popular diagnostic for the studies of basic plasma physics [8][9][10][11][12][13], plasma processing [14][15][16], plasma propulsion [17][18][19][20], among other applications.…”

Section: Introductionmentioning

confidence: 99%

Recent development of LIF diagnostics in ASIPP

Yip,

Jiang,

Jin

et al. 2023

J. Inst.

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In this article, recent research progress of laser induced fluorescence (LIF) diagnostics in ASIPP is reviewed. The fundamental goal of ASIPP's effort on the LIF diagnostics is to develop a working velocity distribution function (VDF) diagnostic to monitor helium ash removal in burning plasmas. Real-time monitoring of helium ash VDF requires consideration in radiation safety, measurement response time, and compatibility of tokamak operation, as well as ion/neutral VDFs with a temperature at possibly >20 eV. These considerations, almost unique to large-scale instruments or specifically to tokamak plasmas, require renewed research and development (R&D) efforts in optical design, automation, and expansion of laser functionality for the LIF diagnostics that were often not considered in conventional applications of the LIF diagnostics. To this end, ASIPP invested a series of research effort into the development of LIF techniques. Signal evaluation has been performed on a diagnostics-test device (LTS), and the obtained signal strength has been extrapolated to tokamak edge and divertor relevant environments with promising results. The extrapolations compared the available solid angle and plasma density between the test device and the design scenario where the LIF diagnostics will potentially be implemented in a tokamak edge and divertor plasma. The estimation neglects the higher density of energetic electrons in the edge and divertor regions, making it a conservative assessment. Automated post-DAQ processing of LIF signals using both “conventional” methods and an AI-augmented method were also explored. Both approaches yielded usable results, but the AI-trained method showed a faster response, which is advantageous for real-time plasma diagnostics. Basic mechanisms of LIF diagnostics were also explored. Specifically, the limitations of lock-in modulation was demonstrated to determine the limitation of time-resolved measurements using such methods. De-modulation and degradation of the LIF signal occurred as the modulation frequency exceeded 1/10th of the fluorescence frequency. This finding sets a practical limit of the modulation frequency up to which we can benefit from lock-in amplification. These published works along with other unpublished progress will be thoroughly discussed in this article to illustrate ASIPP's effort towards the implementation of LIF diagnostics in future tokamak devices and to promote the application of LIF diagnostics in other fields of research.

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“…Therefore, studies on ion acoustic waves [33,34] and a generalized Bohm criterion [35][36][37] depicted this mixture as a simple example for a multi-ion discharge. Recent studies by Kim et al [38] and Adrian et al [39] contributed to those discussions using or referring to Ar/Xe plasmas.…”

Section: Introductionmentioning

confidence: 99%

Ion dynamics in capacitively coupled argon-xenon discharges

Klich,

Wilczek,

Janssen

et al. 2021

Preprint

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An argon-xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radiofrequency discharges are examined utilizing Particle-In-Cell/Monte Carlo Collisions (PIC/MCC) simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data is applied to analyze the findings further. This work focuses on investigating the ion dynamics in a plasma with two ion species and a gas mixture as background. By varying the gas composition and driving voltage of the single-frequency discharge, fundamental mechanics of the discharge, such as the evolution of the plasma density and the energy dispersion, are discussed. Thereby, close attention is paid to these measures' influence on the ion energy distribution functions at the electrode surfaces. The results show that both the gas composition and the driving voltage can significantly impact the ion dynamics. The mixing ratio of argon to xenon allows for shifting the distribution function for one ion species from collisionless to collision dominated. The mixing ratio serves as a control parameter for the ion flux and the impingement energy of ions at the surfaces. Additionally, a synergy effect between the ionization of argon and the ionization of xenon is found and discussed.

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Ion-neutral collision effect on ion-ion two-stream-instability near sheath-presheath boundary in two-ion-species plasmas

Cited by 12 publications

References 21 publications

Sculpted ultracold neutral plasmas

Sculpted ultracold neutral plasmas

Recent development of LIF diagnostics in ASIPP

Ion dynamics in capacitively coupled argon-xenon discharges

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