scholarly journals Introduction: Plasma Parameters and Simplest Models

2020 ◽  
Author(s):  
Eduard Vardges Rostomyan
Keyword(s):  
Quantum Plasma ◽  
Plasma Parameters ◽  
Long Distance ◽  
Plasma Properties ◽  
Neutral Gas ◽  
Plasma State ◽  
Spatial Dimensions ◽  
Basic Parameters ◽  
Debye Radius

Plasma is ionized gas (partially or fully). Overwhelming majority of matter in the universe is in plasma state (stars, Sun, etc.). Basic parameters of plasma state are given briefly as well as classification of plasma types: classic-quantum, ideal-nonideal, etc. Differences between plasma and neutral gas are presented. Plasma properties are determined by long distance electrostatic forces. If spatial dimensions of a system of charged particles exceed the so-called Debye radius, the system may be considered as plasma, that is, a medium with qualitatively new properties. The expressions for Debye radius for classical and quantum plasma are carried out. Basic principles of plasma description are presented. It is shown that plasma is a subject to specific electrostatic (or Langmuir) oscillations and instabilities. Simplest plasma models are given briefly: the model of “test” particle and model of two (electron and ion) fluids. As an example, Buneman instability is presented along with qualitative analysis of its complicate dispersion relation. Such analysis is typical in plasma theory. It allows to easily obtain the growth rate.

Long-pulse plasma source for SMOLA helical mirror

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Ivan A. Ivanov ◽  
V. O. Ustyuzhanin ◽  
A. V. Sudnikov ◽  
A. Inzhevatkina
Keyword(s):  
Magnetic Field ◽  
Gas Flow ◽  
Supply Voltage ◽  
Hydrogen Plasma ◽  
Plasma Source ◽  
Lanthanum Hexaboride ◽  
Plasma Stream ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Plasma Gun

A plasma gun for forming a plasma stream in the open magnetic mirror trap with additional helicoidal field SMOLA is described. The plasma gun is an axisymmetric system with a planar circular hot cathode based on lanthanum hexaboride and a hollow copper anode. The two planar coils are located around the plasma source and create a magnetic field of up to 200 mT. The magnetic field forms the magnetron configuration of the discharge and provides a radial electric insulation. The source typically operates with a discharge current of up to 350 A in hydrogen. Plasma parameters in the SMOLA device are Ti ~ 5 eV, Te ~ 5–40 eV and ni ~ (0.1–1)  × 1019 m−3. Helium plasma can also be created. The plasma properties depend on the whole group of initial technical parameters: the cathode temperature, the feeding gas flow, the anode-cathode supply voltage and the magnitude of the cathode magnetic insulation.

scholarly journals Numerical and Experimental Investigation of Longitudinal Oscillations in Hall Thrusters

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 148
Author(s):  
Vittorio Giannetti ◽  
Manuel Martín Saravia ◽  
Luca Leporini ◽  
Simone Camarri ◽  
Tommaso Andreussi
Keyword(s):  
Discharge Current ◽  
Fluid Model ◽  
Low Frequency ◽  
Hall Thruster ◽  
Hall Thrusters ◽  
Current Signal ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Breathing Mode ◽  
Spatio Temporal

One of the main oscillatory modes found ubiquitously in Hall thrusters is the so-called breathing mode. This is recognized as a relatively low-frequency (10–30 kHz), longitudinal oscillation of the discharge current and plasma parameters. In this paper, we present a synergic experimental and numerical investigation of the breathing mode in a 5 kW-class Hall thruster. To this aim, we propose the use of an informed 1D fully-fluid model to provide augmented data with respect to available experimental measurements. The experimental data consists of two datasets, i.e., the discharge current signal and the local near-plume plasma properties measured at high-frequency with a fast-diving triple Langmuir probe. The model is calibrated on the discharge current signal and its accuracy is assessed by comparing predictions against the available measurements of the near-plume plasma properties. It is shown that the model can be calibrated using the discharge current signal, which is easy to measure, and that, once calibrated, it can predict with reasonable accuracy the spatio-temporal distributions of the plasma properties, which would be difficult to measure or estimate otherwise. Finally, we describe how the augmented data obtained through the combination of experiments and calibrated model can provide insight into the breathing mode oscillations and the evolution of plasma properties.

scholarly journals Effect of the gas puff location on the divertor plasma properties in COMPASS tokamak

2020 ◽  
Vol 1492 (1) ◽  
pp. 012003
Author(s):  
M Dimitrova ◽  
M Tomes ◽  
Tsv Popov ◽  
R Dejarnac ◽  
J Stockel ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Vacuum Chamber ◽  
Plasma Potential ◽  
Saturation Current ◽  
Langmuir Probes ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Low Field ◽  
Saturation Current Density ◽  
Deuterium Gas

Abstract Langmuir probes are used to study the plasma parameters in the divertor during deuterium gas puff injection on the high- (HFS) or low-field sides (LFS). The probe data were processed to evaluate the plasma potential and the electron temperatures and densities. A difference was found in the plasma parameters depending on the gas puff location. In the case of a gas puff on the LFS, the plasma parameters changed vastly, mainly in the inner divertor – the plasma potential, the ion saturation-current density and the electron temperature dropped. After the gas puff, the electron temperature changed from 10-15 eV down to within the 5-9 eV range. As a result, the parallel heat-flux density decreased. At the same time, in the outer divertor the plasma parameters remained the same. We thus concluded that using a gas puff on the LFS will facilitate reaching a detachment regime by increasing the density of puffed neutrals. When the deuterium gas puff was on the HFS, the plasma parameters in the divertor region remained almost the same before and during the puff. The electron temperature decreased with just few eV as a result of the increased amount of gas in the vacuum chamber.

scholarly journals THEORETICAL FUNDAMENTALS OF ESTIMATABILITY ASSESSMENT OF TRAIN SITUATION SIGNS FOR WORK OF INTELLECTUAL LOCOMOTIVE CONTROL SYSTEMS

2021 ◽  
Vol 1 (38) ◽  
pp. 223-231
Author(s):  
O. Gorobсhenko
Keyword(s):  
Control Systems ◽  
Random Search ◽  
Information Value ◽  
Train Control ◽  
Relative Value ◽  
Basic Parameters ◽  
Control Decision ◽  
Definition Of

The article is devoted to the problem of implementation of intelligent control systems in transport. An important task is to assess the information parameters of the control systems. In the existing works the question of definition of one of the basic parameters of functioning of locomotive control systems - information value of separate signs of a train situation is not considered. This does not make it possible to determine the order of signal processing at the input and assess their contribution to the adoption of a control decision. Moreover, informativeness is a relative value, which is expressed in the different information value of a particular feature for the classification of different train situations. Also, the informativeness of the feature may depend on the type of decisive rules in the classification procedure. The quality of recognition of a train situation in which the locomotive crew is, depends on the quality of the features used by the classification system. The decisive criterion for the informativeness of the features in the problem of pattern recognition is the magnitude of losses from errors. To determine the range of the most informative features of train situations, the method of random search with adaptation was used. The results of the work make it possible to optimize the operation of automated and intelligent train control systems by reducing the amount of calculations and simplifying their algorithm.

scholarly journals Self-Consistent Cathode–Plasma Coupling and Role of the Fluid Flow Approach in Torch Modeling

2021 ◽  
Author(s):  
Margarita Baeva ◽  
Tao Zhu ◽  
Thorben Kewitz ◽  
Holger Testrich ◽  
Rüdiger Foest
Keyword(s):  
Mach Number ◽  
Gas Flow ◽  
Stokes Equations ◽  
Cathode Plasma ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Flow Rates ◽  
High Mach Number ◽  
Self Consistent ◽  
High Mach

AbstractA two-dimensional and stationary magnetohydrodynamic model of a plasma spray torch operated with argon is developed to predict the plasma properties in a steady operating mode. The model couples a submodel of a refractory cathode and its non-equilibrium boundary layer to a submodel of the plasma in local thermodynamic equilibrium in a self-consistent manner. The Navier–Stokes equations for a laminar and compressible flow are solved in terms of low and high Mach number numerical approaches. The results show that the Mach number can reach values close to one. Simulations are performed for electric currents of 600 A and 800 A, and gas flow rates of 40, 60, and 80 NLPM. The plasma parameters obtained by the two approaches differ, and the differences become more pronounced for higher currents and gas flow rates. The arc voltage, the electric power, and the thermal efficiency from both the low and high Mach number models of the plasma agree well with experimental findings for a current of 600 A and a flow rate of 40 NLPM. For higher currents and gas flow rates, the results of the low and high Mach number models gradually differ and underline the greater appropriateness of the high Mach number model.

scholarly journals OPERATIONAL CHARACTERISTICS OF THE ELECTRON ACCELERATOR BASED ON THE PLASMA-FILLED DIODE

2021 ◽  
pp. 78-83
Author(s):  
E.I. Skibenko ◽  
A.N. Ozerov ◽  
I.V. Buravilov ◽  
V.B. Yuferov
Keyword(s):  
Plasma Density ◽  
Electron Accelerator ◽  
Plasma Parameters ◽  
Atomic Collisions ◽  
Elementary Processes ◽  
Neutral Gas ◽  
Operational Characteristics ◽  
Discharge Gap

The paper is concerned with the plasma-filled diode performance in the intensive mode regulated by means of external gas puffing. The possibility to smoothly vary the plasma parameters in the discharge gap zone, and thus, to optimize the main diode characteristics (Ucutoff, Icutoff) by the external gas puffing method has been confirmed by experiment. The introduction of additional quantity of neutral gas into the discharge causes the change in the plasma density balance due to elementary processes in physics of electronic and atomic collisions, such as ionization, dissociation, recombination. The deviation of actual voltage/current values from their maximum values can be attributed to the mismatch in the generator-load feed circuit.

scholarly journals Positive polarity predicates

Linguistics ◽  
2018 ◽  
Vol 56 (2) ◽  
pp. 361-400 ◽  
Author(s):  
Jack Hoeksema
Keyword(s):  
Binary Classification ◽  
Complex Interaction ◽  
Positive Polarity ◽  
Long Distance ◽  
Recent Proposal ◽  
Polarity Items ◽  
Semantics And Pragmatics ◽  
Negative Quantifiers ◽  
High Degree

Abstract This paper presents Dutch and English predicates that behave as positive polarity items and provides a partial, semantically-grounded classification of this group of PPIs. The items are studied from the perspective of anti-licensing behavior (by negation, either locally or long-distance, in questions, and by weakly negative quantifiers such as little and few). Predicates, unlike quantifiers, do not have wide scope readings (which allow quantificational PPIs such as somebody to appear in the syntactic scope of negation). Using a mixture of corpus data and introspective judgments, we show that anti-licensing among PPIs is not uniform (mirroring earlier results on NPIs which likewise show considerable variation). Rescuing contexts are likewise shown to differ among PPIs. Some of the PPI predicates show complex interaction with illocutionary force (especially mandative force), and others with differences between presupposed and asserted propositions. High degree predicates, finally, point toward the existence of connections between the marking of degree and positive polarity. PPI status is argued to be the result of a complex interaction between the effects of negation and other nonveridical operators, and other semantic factors, which differ among subclasses of PPIs. Anti-licensing by weak negation correlates fairly well with anti-licensing by long-distance negation, a finding which is (partly) in line with a recent proposal by Spector (2014, Global positive polarity items and obligatory exhaustivity. Semantics and Pragmatics 7(11). 1–61) concerning global PPIs. However, we find there to be more variation among the PPIs studied here than the classification of Spector (2014) or any binary classification stipulates.

scholarly journals Classification of topological insulators and superconductors in three spatial dimensions

2008 ◽  
Vol 78 (19) ◽  
Author(s):  
Andreas P. Schnyder ◽  
Shinsei Ryu ◽  
Akira Furusaki ◽  
Andreas W. W. Ludwig
Keyword(s):  
Topological Insulators ◽  
Spatial Dimensions

Spectroscopic Study and Amorphous Film Deposition in RF and Pulsed Plasma Processings

1988 ◽  
Vol 117 ◽  
Author(s):  
Kenji Ebihara ◽  
Seiji Kanazawa ◽  
Sadao Maeda
Keyword(s):  
Processing System ◽  
Optical Emission ◽  
Quantitative Relationship ◽  
Amorphous Film ◽  
Film Deposition ◽  
Rf Discharge ◽  
Pulsed Plasma ◽  
Plasma Parameters ◽  
Optical Emission Spectrum ◽  
Plasma State

AbstractProcessing plasmas generated by three types of discharges are diagnosed spectroscopically in order to estimate the quantitative relationship between plasma parameters and electrical and optical properties of deposited materials. An rf discharge is capacitively produced by a 13.56 MHz rf oscillator. A microwave generator operating at 2.45 GHz is used to supply power to a discharge cavity. Further a pulsed plasma which is inductively generated by pulsed current ( 70 kA peak ) is applied to study dissociation process in the transient plasma and possibility of a novel processing system. The gases used are methane for amorphous carbon formation and silane for amorphous silicon deposition. Measurements of optical emission spectrum are performed to estimate the processing plasma state by the relative spectral intensity method and the Doppler-broadening method.

scholarly journals Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

2016 ◽  
Vol 34 (3) ◽  
pp. 357-367 ◽  
Author(s):  
Takuma Nakamura ◽  
Rumi Nakamura ◽  
Hiroshi Haseagwa
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Real Space ◽  
Diffusion Region ◽  
Electron Mass ◽  
Plasma Parameters ◽  
Electron Diffusion ◽  
Background Density ◽  
Spatial Dimensions ◽  
Inner Region

Abstract. Spatial dimensions of the detailed structures of the electron diffusion region in anti-parallel magnetic reconnection were analyzed based on two-dimensional fully kinetic particle-in-cell simulations. The electron diffusion region in this study is defined as the region where the positive reconnection electric field is sustained by the electron inertial and non-gyrotropic pressure components. Past kinetic studies demonstrated that the dimensions of the whole electron diffusion region and the inner non-gyrotropic region are scaled by the electron inertial length de and the width of the electron meandering motion, respectively. In this study, we successfully obtained more precise scalings of the dimensions of these two regions than the previous studies by performing simulations with sufficiently small grid spacing (1∕16–1∕8 de) and a sufficient number of particles (800 particles cell−1 on average) under different conditions changing the ion-to-electron mass ratio, the background density and the electron βe (temperature). The obtained scalings are adequately supported by some theories considering spatial variations of field and plasma parameters within the diffusion region. In the reconnection inflow direction, the dimensions of both regions are proportional to de based on the background density. Both dimensions also depend on βe based on the background values, but the dependence in the inner region ( ∼ 0.375th power) is larger than the whole region (0.125th power) reflecting the orbits of meandering and accelerated electrons within the inner region. In the outflow direction, almost only the non-gyrotropic component sustains the positive reconnection electric field. The dimension of this single-scale diffusion region is proportional to the ion-electron hybrid inertial length (dide)1∕2 based on the background density and weakly depends on the background βe with the 0.25th power. These firm scalings allow us to predict observable dimensions in real space which are indeed in reasonable agreement with past in situ spacecraft observations in the Earth's magnetotail and have important implications for future observations with higher resolutions such as the NASA Magnetospheric Multiscale (MMS) mission.

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