Determination Of Plasma Parameters Research Articles

Central Collisions of Charged Dust Particles in a Plasma

Elastic dust particle particle interaction in an rf plasma provides a charge measurement method independent of the knowledge of plasma parameters. Assuming a screened Coulomb potential surrounding each particle with a constant charge at fixed plasma conditions, the charge and the screening length can be calculated from the trajectories of two colliding particles. With this method, we determine the charge and screening length of dust particles in the sheath of an rf discharge. The method can also be used to determine plasma parameters taking the dust particles as local probes.

Ion temperature measuring probe in a strongly magnetized plasma

A probe for the measurement of the ion temperature in a strongly magnetized plasma is described. The positive-ion current to a cylindrical probe, whose axis is set parallel to the magnetic field, is calculated in the collision-free regime as a function of the ion temperature and the magnetic-field strength. It is assumed that the electron Larmor radius is negligibly small compared to the radius of the cylinder. Only the ion Larmor radius is treated as finite. The ion temperature can be evaluated from the ratio of ion currents of the two cylindrical electrodes with different lengths, whose surfaces are parallel to the magnetic field. The effect of ion drift along the cylinder axis is also considered. Experiments have been made in the edge plasma of a JFT-2M tokamak to test the above probe for determining plasma parameters during ohmic and NBI heatings.

Fe III emission lines in the optical spectrum of the planetary nebula IC 4997

view Abstract Citations (20) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Fe III Emission Lines in the Optical Spectrum of the Planetary Nebula IC 4997 Keenan, F. P. ; Aller, L. H. ; Hyung, S. ; Conlon, E. S. ; Warren, G. A. Abstract Relative populations for the 17 fine-structure levels in the 5D, 3P, 3H, 3F, and 3G states of the 3d6 configuration in Fe III, calculated using electron impact excitation rates derived with the R-matrix code, are used to derive theoretical electron temperature and density sensitive emission-line ratios applicable to the spectra of astronomical objects in the 4607-5412 A wavelength range. A comparison of these with high spectral resolution observational data for the PN IC 4997 reveals generally good agreement between theory and observation. This provides experimental support for the accuracy of the theoretical ratios and illustrates their usefulness in determining plasma parameters for the Fe III-emitting region of a gaseous nebula. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/172760 Bibcode: 1993ApJ...410..430K Keywords: Emission Spectra; Iron; Planetary Nebulae; Visible Spectrum; Electron Density (Concentration); Electron Energy; Electron Transitions; Astrophysics full text sources ADS | data products SIMBAD (1)

Determination of plasma parameters from plane-probe characteristics in a current-carrying plasma

The authors present an approximate method of determining the temperature and the drift velocity of electrons in a current-carrying plasma. An approximate expression for the determination of plasma density is also derived. The authors consider the probe characteristics obtained by a one-sided plane probe in a plasma in which the electron distribution may be assumed to be a shifted Maxwellian. The method they propose for analysing such characteristics can be regarded as a generalization of the standard probe method for the determination of plasma parameters in a Maxwellian plasma. Application of the method is illustrated by experimental examples. A confirmation of the method is performed by comparing the results with those obtained by other techniques.

Time resolved neutron yield measurements on FT device

A system of four BF 3 proportional chambers for time resolved neutron yield measurements is operative on the FT (Frascati Torus) device. The determination of plasma parameters from neutron yield measurements is a relatively new field of investigation subjected to continuous improvements, also in view of feasible application to the control of future fusion reactors. The absolute calibration of neutron detectors in the presence of extended neutron sources and large scattering masses, such as tokamak devices, presents the major problem. Techniques employed for BF 3 chamber calibration are presented. In thermonuclear plasmas the neutron yield is related to ion temperature through the density. On FT device, neutron yield measurements and charge exchange analysis are the only routine methods of monitoring ion temperature. The method and results for this measurement are presented. Neutron yield measurements in fusion devices give quantative and qualitative informations about ion velocity and nonthermonuclear neutron sources. The results of neutron yield measurements in different working regimes of the FT device are presented.

Helios observational constraints on solar wind expansion

Helios particle and magnetic field observations between 0.3 and 1 AU are used to determine plasma parameters that characterize the bulk and internal energy state of the solar wind. Quantities expected to be conserved in a time‐stationary flow with local spherical symmetry in the ecliptic plane are actually found to be invariant within measurement uncertainties. These are the total mass, energy, and angular momentum fluxes for the anisotropic solar wind plasma composited by electrons, protons, and alphas. Although individual species have nonthermal velocity distributions, the total plasma pressure is almost isotropic (p⊥/p∥ = 0.9). The total heat flux divided by the mass flux Qr/ρur is markedly smaller than thermal speeds squared υ∥,⊥² = p∥,⊥/ρ. By this reason an appropriately defined polytropic index γ is found to be almost 5/3 and rather insensitive to heliocentric distance and flow speed. This index γ does not include terms due to wave turbulence or external heat sources but is solely based on the total particle heat flux. These observational findings indicate that the heat flux beyond 0.3 AU is observationally too small to cause a strong departure from adiabaticity. The solar wind expansion may be conceived in terms of a “single particle” moving in the binding gravitational potential and in the accelerating thermal (enthalpy and heat fluxes) and magnetorotational (azimuthal kinetic energy and Poynting flux) potentials. The radial profiles of these potentials are derived from observations.

Temperature Field Measurements of the Electric Arc Plasma in a Longitudinal Magnetic Field

AbstractTwo methods are described to determine local parameters of the unsteady asymmetric plasma. The basis of one method is the parametric approach. This method is used to determine plasma parameters in the case when an assumption can be made on the shape of the intensity isolines. The temperature field was calculated according to the intensity distributions in X direction obtained simultaneously from two lines of sight. The second method was applied for measurements in arbitrary plasma configuration. In this case the temperature fields were calculated according to measurements from lines of sight simultaneously, and the obtained data were used in the Radon transformation inversion.

Limit on rotational energy available to excite Jovian aurora

There is a fundamental relationship between the power that is extracted from Jupiter's rotation to drive magnetospheric processes and the rate at which mass is injected into the Io plasma torus. Half of this power is consumed by bulk motion of the plasma and the other half represents an upper limit on the energy from rotation available for dissipation and in particular to excite the Jovian aurora. Since the rotation of the planet is the only plausible source of energy, the power inferred from the observed auroral intensities requires a plasma injection rate of 2.6 × 1029 AMU/sec or greater. This in turn leads to a residence time of a torus particle of 48 d. or less. These results raise doubts about the applicability of equilibrium thermodynamics to the determination of plasma parameters in the Io torus.

A magnetically shielded sampling technique for plasma diagnostics in a medium-pressure magnetoplasma

A magnetically shielded sampling technique is developed which permits determination of plasma parameters by orifice probe, electrostatic analyser or mass spectrometer for medium-pressure magnetised plasmas. Experimental results show that: for a retarded-electron current no abnormal peak or non-exponential potential dependence of current potential characteristics as observed by previous orifice probe measurements in a magnetised plasma is observed; electron temperature measurements agree to within 10% with recent positive-column electron temperature theory; and plasma density measurements agree to within a factor of 3 with electrostatic probe measurements.

Determination of plasma parameters from soft X-ray images for coronal holes /open magnetic field configurations/ and coronal large-scale structures /extended closed-field configurations/

In connection with high-quality solar soft X-ray images the 'quiet' features of the inner corona have been separated into two sharply different components, including the strongly reduced emission areas or coronal holes (CH) and the extended regions of looplike emission features or large-scale structures (LSS). Particular central meridian passage observations of the prominent CH1 on August 21, 1973, are selected for a quantitative study. Histogram photographic density distributions for full-disk images at other central meridian passages of CH 1 are also presented, and the techniques of converting low photographic density data to deposited energy are discussed, with particular emphasis on the problems associated with the CH data.

Transient characteristics of a planar Langmuir probe

The technique of determining plasma parameters from the transient characteristics of a Langmuir probe has a number of advantages over the method which uses a probe operating under steady-state conditions [1]. The dynamic characteristics of a probe must also be considered in cases where the plasma is highly nonstationary.

Determination of plasma parameters from the intensity of the continuous spectrum

The relation between the spectral intensity of the recombination radiation and the recombination coefficient has been studied. It is shown that the electron temperature can be determined from the intensity of the continuous spectrum, even when the ratio of the recombination-radiation and bremsstrahlung intensities is unknown. Methods have been developed for determining the recombination coefficients and the electron velocity distribution with respect to the intensity of the continuous spectrum.

Determination of plasma parameters by means of a multi-beam radiointerferometer

Determination of plasma parameters by means of a multi-beam radiointerferometer

Nomogram for the Correction of Ion Saturation Current in The Instantneous Triple-Probe Measurement

A basic consideration on the mechanism of ion sheath formation was made, and the Child-Langmuir space charge equation was used to calculate the Ion Current-Voltage Characteristics of an electrostatic probe as well as the theoretical value of the β which was defined as the gradient of the scivare of the ion current with probe potential. (1) A nomogram based upon the estimated theoretical value of β is presented for the rapid and accurate determination of plasma parameters from the usual-Triple-Probe datas in which β=0 is assumed.Experimental confirmations were made through the measurements of some stationary plasmas, and the advantage of the nomogram has been verified.

On geomagnetic sudden commencements, sudden impulses, and storm durations : Matsushita, S., High Altitude Observatory, Boulder, Colorado, Journal of Geophysical Research, Sept., 1962, 25 pp.

It is common to use imaging instruments such as EUV and X-ray imagers and coronagraphs to study large-scale phenomena such as coronal mass ejections and coronal waves. Although high resolution spectroscopy is generally limited to a small field of view, its importance in understanding global phenomena should not be under-estimated. I will review current spectroscopic observations of large-scale dynamic phenomena such as global coronal waves and coronal mass ejections. The aim is to determine plasma parameters such as flows, temperatures and densities to obtain a physical understanding of these phenomena.

Physical conditions in limb flares and active prominences. VI. Selective excitation conditions : Tandberg-Hanssen, Einar, The Astrophysical Journal, Vol. 137, No. 1, January, 1963, 15 pgs.

It is common to use imaging instruments such as EUV and X-ray imagers and coronagraphs to study large-scale phenomena such as coronal mass ejections and coronal waves. Although high resolution spectroscopy is generally limited to a small field of view, its importance in understanding global phenomena should not be under-estimated. I will review current spectroscopic observations of large-scale dynamic phenomena such as global coronal waves and coronal mass ejections. The aim is to determine plasma parameters such as flows, temperatures and densities to obtain a physical understanding of these phenomena.