Search results for "Plasma parameters"

Measuring the electron temperatures of coronal mass ejections with future space-based multi-channel coronagraphs: a numerical test

2018

Context. The determination from coronagraphic observations of physical parameters of the plasma embedded in coronal mass ejections (CMEs) is of crucial importance for our understanding of the origin and evolution of these phenomena. Aims. The aim of this work is to perform the first ever numerical simulations of a CME as it will be observed by future two-channel (visible light VL and UV Ly-α) coronagraphs, such as the Metis instrument on-board ESA-Solar Orbiter mission, or any other future coronagraphs with the same spectral band-passes. These simulations are then used to test and optimize the plasma diagnostic techniques to be applied to future observations of CMEs. Methods. The CME diagno…

Vessel noise pollution as a human threat to fish: assessment of the stress response in gilthead sea bream (Sparus aurata, Linnaeus 1758)

2016

This study examined the effects of boat noise pollution on the stress indices of gilthead sea bream (Sparus aurata, Linnaeus 1758). To assess the stress response in these fish, biometric values and plasma parameters such as ACTH, cortisol, glucose, lactate, haematocrit, Hsp70, total protein, cholesterol, triglycerides and osmolarity were analysed. After acclimatization of the animals, the experiment was carried out in a tank fitted with underwater speakers where the fish were exposed to sound treatments (in duplicate) consisting of: 10 days of no sound (control treatment; the animals were only exposed to the experimental tank’s background noise) and 10 days of noise derived from original re…

Plasma Parameters of the Endocannabinoid System Are Unaltered in Fibromyalgia.

2018

Diagnostics of Helium-Argon Arc Discharge Plasma Based on Spectral Line Shape Measurements

1999

Electron densities and ion (gas) temperatures on the axis of an arc discharge plasma, produced at atmospheric pressure in a gas mixture of 95% helium and 5% argon, are determined at two arc currents. The evaluation of both main plasma parameters is based on line shape measurements, the ion temperature on the Doppler broadening of selected ArII lines, while the electron density on the Stark broadening of the hydrogen Hp line which appear in the spectrum due to hydrogen traces in the applied gases. The significance of reliable plasma diagnostics for determination of atomic structure data is discussed.

High-frequency electrodeless discharges in helium

2004

Modelling of high-frequency electrodeless discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma?field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electroma…

Fabry–Pérot lineshape analysis in an optically thick expanding plasma

2007

In this work the authors present Fabry–Perot measurements of Ar atom spectral line profiles originating from the expansion of an Ar–N2 thermal plasma into a low pressure environment. The plasma is characterized by strong density, temperature and velocity gradients and it offers a high degree of light absorption for some gas mixtures. First, it is demonstrated that the Abel inversion method cannot be applied under such conditions even if absorption is absent. Second, two approaches are examined to obtain plasma parameters in the case of an optically thick expanding plasma. It is shown that velocity and temperature development along the jet radius can be inferred from experimental lineshapes …

Study of Gasdynamic Electron Cyclotron Resonance Plasma Vacuum Ultraviolet Emission to Optimize Negative Hydrogen Ion Production Efficiency

2019

Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet (VUV) emission. Studying the VUV radiation therefore provides volumetric rates of plasma-chemical processes and plasma parameters. In the past we have used gasdynamic ECR discharge for volumetric negative ion production and investigated the dependencies between the extracted H$^-$ current density and various ion source parameters. It was shown that it is possible to reach up to 80 mA/cm$^2$ of negative ion current density with a two electrode extraction. We report experime…

First experiments with gasdynamic ion source in CW mode.

2016

A new type of ECR ion source—a gasdynamic ECR ion source—has been recently developed at the Institute of Applied Physics. The main advantages of such device are extremely high ion beam current with a current density up to 600–700 emA/cm2 in combination with low emittance, i.e., normalized RMS emittance below 0.1 π mm mrad. Previous investigations were carried out in pulsed operation with 37.5 or 75 GHz gyrotron radiation with power up to 100 kW at SMIS 37 experimental facility. The present work demonstrates the first experience of operating the gasdynamic ECR ion source in CW mode. A test bench of SMIS 24 facility has been developed at IAP RAS. 24 GHz radiation of CW gyrotron was used for p…

Liquid gallium jet–plasma interaction studies in ISTTOK tokamak

2009

Abstract Liquid metals have been pointed out as a suitable solution to solve problems related to the use of solid walls submitted to high power loads allowing, simultaneously, an efficient heat exhaustion process from fusion devices. The most promising candidate materials are lithium and gallium. However, lithium has a short liquid state temperature range when compared with gallium. To explore further this property, ISTTOK tokamak is being used to test the interaction of a free flying liquid gallium jet with the plasma. ISTTOK has been successfully operated with this jet without noticeable discharge degradation and no severe effect on the main plasma parameters or a significant plasma conta…

Comparison of hydrogen Balmer-alpha Stark profiles measured at high electron densities with theoretical results

2005

Profiles of the H-alpha line calculated using the full computer simulation method (FCSM) and the standard theory (ST) agree excellently with a measured profile (at an electron density of Ne = 9.0 × 1016 cm−3 and temperature T = 12 600 K) in an argon–hydrogen (minority) arc plasma. Calculated widths (FCSM) and shifts (ST) also agree well with experimental data from flash-tube plasmas and gas-linear pinch plasmas. Some discrepancies are probably caused by experimental flaws. Our analysis of the so-called generalized theory (GT) shows that this theory is burdened with un-physical approximations, and consequently so are all subsequent modifications based on GT. It is shown that the so-called ac…