Plasma diagnostics for complex plasmas under microgravity and on ground

AbstractComplex plasmas are low-temperature plasmas containing micron-sized particles (microparticles) such as dust grains. These are present in astrophysical systems (comets, molecular clouds, et al.) and in technological applications (microchip production by plasma etching, deposition of solar cells, et al.). Complex plasmas are also of interest in basic science because these are often used as models for many other strongly coupled many-body systems in solid state, fluid, or plasma physics. Since gravity has a strong influence on the microparticle component, experiments under microgravity (parabolic flights, sounding rockets, International Space Station (ISS)) are performed. Interaction between microparticles depends on plasma parameters such as ion density or ion temperature. Also, the presence of microparticles may change the properties of background plasma. Therefore, the background plasma needs to be characterized to provide adequate interpretation of the microgravity experiments. For this purpose a dedicated high-speed diagnostic system has been set up.

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Plasma diagnostics by laser spectroscopic electric field measurement

Pure and Applied Chemistry ◽

10.1351/pac200577020345 ◽

2005 ◽

Vol 77 (2) ◽

pp. 345-358 ◽

Cited By ~ 12

Author(s):

U. Czarnetzki ◽

D. Luggenhölscher ◽

V. A. Kadetov ◽

H. F. Döbele

Keyword(s):

Electric Field ◽

Density Distribution ◽

Field Measurements ◽

Distribution Functions ◽

Plasma Parameters ◽

Ion Density ◽

Versatile Tool ◽

Low Temperature Plasmas ◽

Energy Distribution Functions ◽

Laser Spectroscopic

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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Assessment of the impact of kinetic effect of ion parallel heat conduction on DEMO relevant SOL plasma using integrated SOL-divertor code SONIC

Plasma Physics and Controlled Fusion ◽

10.1088/1361-6587/ac48bd ◽

2022 ◽

Author(s):

Yuki Homma

Keyword(s):

Heat Conductivity ◽

Mean Free Path ◽

Limiting Factor ◽

Kinetic Effect ◽

Ion Temperature ◽

Plasma Parameters ◽

Ion Density ◽

Tokamak Reactor ◽

Higher Temperature ◽

The Impact

Abstract In plasmas of relatively lower collisionality, such as scrape-off layer (SOL) of fusion tokamak device, parallel heat conductivity of plasma ion becomes smaller than expected by the classical Spitzer-Harm model due to nonlocal kinetic effect. We have assessed, by simulation, impact and role of such kinetic effect of ion heat conductivity (abbreviated by ion KE in this paper) on DEMO relevant tokamak SOL plasma, supposing Japanese demonstration tokamak reactor concept JA DEMO. A series of test simulation, where the ion KE is modeled by a widely used Free-streaming energy (FSE) limited model, has demonstrated the following significant impact of the ion KE on JA DEMO SOL plasma at the baseline operation scenario: (1) the ion KE decreases the ion parallel heat flux density around X-point and further upstream of low field side (LFS) area along the separatrix, where the parallel collisionality tends to decrease due to combination of higher temperature, lower density (i.e. longer mean free path of ion collisions) and higher temperature gradient (shorter characteristic length). Up to 40-60 % of decrease, compared to the case w/o ion KE, is observed among the tested cases where the ion KE level, specified by parameter αi in the FSE-limited model, is scanned over the possible range 0.2 < αi < 2.0. (2) The ion KE leads to significant increase in the ion temperature Ti (up to 600 % of increase among the tested cases) and significant decrease in the ion density ni (up to -80 % of decrease among the tested cases), widely over SOL upstream. By energy balance analysis, it has been suggested that the ion KE affects the upstream ni and Ti, respectively by power of 0.4 and -0.4 of the flux limiting factor, around the separatrix upstream as far as spatial change in plasma parameters are moderate. The results of this study serve as a fundamental assessment of the ion KE for DEMO relevant SOL plasma, clarifying the need of further sophistication of the modeling toward quantitaive prediction.

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Electrostatic wave breaking limit in a cold electronegative plasma with non-Maxwellian electrons

Scientific Reports ◽

10.1038/s41598-021-85228-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

I. S. Elkamash ◽

I. Kourakis

Keyword(s):

Wave Breaking ◽

Density Ratio ◽

Negative Ions ◽

First Integral ◽

Energy Balance Equation ◽

Plasma Parameters ◽

Ion Density ◽

Electrostatic Wave ◽

Nonthermal Electrons ◽

Electronegative Plasma

AbstractA one-dimensional multifluid hydrodynamic model has been adopted as basis for an investigation of the role of suprathermal electrons on the wave breaking amplitude limit for electrostatic excitations propagating in an electronegative plasma. A three-component plasma is considered, consisting of two inertial cold ion populations of opposite signs, evolving against a uniform background of (non-Maxwellian) electrons. A kappa-type (non-Maxwellian) distribution function is adopted for the electrons. By employing a traveling wave approximation, the first integral for the fluid-dynamical system has been derived, in the form of a pseudo-energy balance equation, and analyzed. The effect of intrinsic plasma parameters (namely the ion density ratio, the ion mass ratio, and the superthermal index of the nonthermal electrons) on the wave breaking amplitude limit is explored, by analyzing the phase space topology of the associated pseudopotential function. Our results are relevant to particle acceleration in Space environments and to recent experiments based on plasma-based accelerator schemes, where the simultaneous presence of negative ions and nonthermal electrons may be observed.

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Measurement of the electrical properties of a flowing plasma, including a critical comparison of probe experiment and theory

Journal of Plasma Physics ◽

10.1017/s0022377800004293 ◽

1969 ◽

Vol 3 (2) ◽

pp. 161-178 ◽

Cited By ~ 2

Author(s):

E. W. Billington

Keyword(s):

Major Axis ◽

Wire Mesh ◽

Ion Temperature ◽

Plasma Parameters ◽

Direct Exposure ◽

Current Voltage ◽

Double Electrode ◽

Flowing Plasma ◽

Current Voltage Characteristics ◽

Mesh Grid

The primary quantities characterizing the electricaJ carriers of a flowing plasma in a low density wind tunnel have been determined from measurements using electrostatic probes immersed in the plasma. With the exception of the ion temperature, the plasma parameters have been obtained from the current—voltage characteristics of two types of single electrode probe. The probes consist of a cylinder, the major axis of which is aligned parallel to the flow of the plasma, and a disk, the exposed surface of which is normal to the direction of flow. Experiments with a double electrode probe consisting of a disk-shaped collector electrode which is screened from direct exposure to the plasma by a fine wire mesh, grid electrode, made it possible to obtain current—voltage characteristics with the ion and electron components separated from one another. From the current—voltage characteristic corresponding to collection of ions, using the screen grid probe, values of the ion temperature and drift velocity have been obtained. The measurements have been made at various points along the centre line of flow, for one particular value of the flow rate using argon as the test gas. For a given position of the probes, one value of the ion temperature has been evaluated, together with two independent values of each of the other primary quantities characterizing the electrical carriers of a flowing plasma. Each pair of values agree satisfactorily amongst themselves, good agreement being generally obtained between probe theory and experiment.

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Needed Additions to the Diagnostic System of High-Speed Lines

International Scientific Conference Energy Management of Municipal Facilities and Sustainable Energy Technologies EMMFT 2019 - Advances in Intelligent Systems and Computing ◽

10.1007/978-3-030-57450-5_43 ◽

2020 ◽

pp. 496-505

Author(s):

Viktor Pevzner ◽

Kirill Shapetko ◽

Alexander Slastenin

Keyword(s):

High Speed ◽

Diagnostic System

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A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

MATEC Web of Conferences ◽

10.1051/matecconf/201814503004 ◽

2018 ◽

Vol 145 ◽

pp. 03004

Author(s):

Polya Dobreva ◽

Olga Nitcheva ◽

Monio Kartalev

Keyword(s):

Magnetic Field ◽

Field Model ◽

Specific Aspect ◽

Plasma Parameters ◽

Ion Density ◽

Magnetic Field Model ◽

Wind Spacecraft ◽

The Mean ◽

The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

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Numerical analysis of the neutral beam attenuation rate on the HT-7 and EAST tokamaks

Journal of Plasma Physics ◽

10.1017/s0022377807006502 ◽

2008 ◽

Vol 74 (1) ◽

pp. 9-19 ◽

Cited By ~ 1

Author(s):

GUOPING ZHANG ◽

LIQUN HU ◽

XIANMEI ZHANG ◽

JUAN HUANG ◽

JIN LIU ◽

...

Keyword(s):

Electron Density ◽

Neutral Beam ◽

Beam Power ◽

Impurity Effect ◽

Atomic Processes ◽

Ion Temperature ◽

Plasma Parameters ◽

Beam Attenuation ◽

Attenuation Rate ◽

Temperature Electron

AbstractA diagnostic neutral beam (DNB) is applied to measure the plasma ion temperature and rotation speed in the HT-7 tokamak. Also, a heating neutral beam (HNB) is suggested as an effective method of heating a plasma for the EAST tokamak. As a necessary step to evaluate the required beam power in both applications, the attenuation of the injected neutral beam has been numerically calculated and analyzed considering the effect of various plasma parameters, such as electron temperature, electron density, impurity concentration, and so on. Three basic atomic processes are considered here. It is shown that at the same electron density neutral beam particles can penetrate deeper at higher injection energies and a DNB with the same full energy can attenuate faster at higher electron densities. The impurity effect on the attenuation of a DNB is discussed, and the attenuation of a HNB on the EAST tokamak is also considered.

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The role of BT-dependent flows on W accumulation at the edge of the confined plasma

Nuclear Fusion ◽

10.1088/1741-4326/ac3fe7 ◽

2021 ◽

Author(s):

Shawn Angelo Zamperini ◽

J.H. Nichols ◽

Peter C. Stangeby ◽

David Donovan ◽

Jonah David Duran ◽

...

Keyword(s):

Experimental Evidence ◽

Background Plasma ◽

Ion Temperature ◽

Plasma Flows ◽

Ion Temperature Gradient ◽

Deposition Patterns ◽

Metal Rings ◽

Impurity Transport ◽

Radial Diffusion Coefficient

Abstract Near-separatrix impurity accumulation between the crown and the outer midplane of tokamaks is a common feature in results from codes such as SOLPS-ITER and DIVIMP; however, experimental evidence of accumulation has only recently been obtained and is reported here. The codes find that the poloidal distribution of impurity ions in the scrape-off layer (SOL) depends primarily on toroidal field (BT)-dependent parallel flow patterns of the background plasma and the parallel ion temperature gradient (∇||Tion) force. Experimentally, Mach probes used in L-mode plasmas with favorable (for H-mode access) BT measure fast (M~0.3-0.5) inner-target-directed (ITD) background plasma flows at the crown of single-null discharges. This study reports a set of DIVIMP simulations for two similar H-mode discharges from the DIII-D W Metal Rings Campaign differing primarily in BT-direction to assess the effect that fast ITD flows have on the distribution of W ions in the SOL. It is found that for imposed ITD flows of M = 0.3, W ions that otherwise accumulate due to the ∇||Tion-force are largely flushed out. It is also found that doubling the radial diffusion coefficient from 0.3 to 0.6 m2/s prevents accumulation due to rapid cross-field transport into the far-SOL, where background plasma flows drain W ions to the divertors. Far-SOL W distributions from DIVIMP are then used to specify input to the impurity transport code 3DLIM, which is used to interpretively model collector probe deposition patterns measured in the “wall-SOL.” It is demonstrated that the deposition patterns are consistent with the DIVIMP predictions of near-SOL accumulation for the unfavorable-BT direction, and little/no accumulation for the favorable-BT direction. The wall-SOL collector probes have thus provided the first experimental evidence, albeit indirect, of near-SOL W accumulation – finding it occurs for the unfavorable-BT direction only. For the favorable-BT direction, fast flows can largely prevent accumulation from occurring.

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Direct observations of blob deformation during a substorm

Annales Geophysicae ◽

10.5194/angeo-33-525-2015 ◽

2015 ◽

Vol 33 (5) ◽

pp. 525-530 ◽

Cited By ~ 3

Author(s):

T. Ishida ◽

Y. Ogawa ◽

A. Kadokura ◽

K. Hosokawa ◽

Y. Otsuka

Keyword(s):

High Speed ◽

Temporal Evolution ◽

Dissociative Recombination ◽

Helmholtz Instability ◽

Plasma Parameters ◽

Flow Shear ◽

Expansion Phase ◽

Incoherent Scatter ◽

Direct Observations ◽

Transportation Process

Abstract. Ionospheric blobs are localized plasma density enhancements, which are mainly produced by the transportation process of plasma. To understand the deformation process of a blob, observations of plasma parameters with good spatial–temporal resolution are desirable. Thus, we conducted the European Incoherent Scatter radar observations with high-speed meridional scans (60–80 s) during October and December 2013, and observed the temporal evolution of a blob during a substorm on 4 December 2013. This paper is the first report of direct observations of blob deformation during a substorm. The blob deformation arose from an enhanced plasma flow shear during the substorm expansion phase, and then the blob split into two smaller-scale blobs, whose scale sizes were more than ~100 km in latitude. Our analysis indicates that the Kelvin–Helmholtz instability and dissociative recombination could have deformed the blob structure.

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