[en] In the vast majority of plasmas produced in the JET tokamak the x-ray emission at energies above about 1 keV is dominated by bremsstrahlung radiation from the background deuterium ions, and both bremsstrahlung and recombination radiation from one or two light impurity species such as beryllium and carbon. Under these circumstances local values of impurity densities and concentrations, or alternatively of the effective charge Z_eff of the ion mixture, are derived from tomographic measurements of the local x-ray emissivity at energies above 1--3 keV, in conjunction with measurements of electron density and temperature profiles. These calculations are performed using the intrinsic emissivities due to the impurity ions. The emissivities into the relevant energy bands, determined by the detector and filter characteristics, were calculated assuming coronal ionization equilibrium, and tabulated as a function of electron temperature. This method offers a good spatial and temporal resolution, and is successfully applied to most plasma conditions where the relative proportions of impurities are known. We also present a detailed sensitivity study to assess the effects of errors in the input data, and a comparison with established methods based on visible bremsstrahlung measurements, and charge exchange spectroscopy

[en] The outlook of X-ray spectroscopy for study of collisions of electrons with multiply charged ions in dense laser produced plasmas is discussed. The data on dielectronic recombination rate coefficients as well as on transition rates between excited states are obtained. The experimental evidence of decreasing of recombination rate with the electron density increasing is given. The corresponding experimental data for He-like Mg, Ca, Ti and Fe ions are presented. (Auth.)

[en] Results of experimental study on control of the plasma filament position in the ''Tuman-3'' adiabatic-compression tokamak are given. The control system of the vertical plasma filament position consists of two circuits. The system provides the 10 Gs/ms field growth rate on the plasma current front and 57 Gs/ms on the plateau. The control system of the horizontal plasma filament position consists of a capacitor battery (400 V, 2.5 kA, 600 kJ), a vertical field fast winding, a filament position measurement system. The maximum winding field is 90 Gs. The 1 to 1.5 cm displacement to the magnetic surface centre is shown to correspond to optimum operating conditions of the tokamak. The experimental results testifying to the correlation between the ion tempe-- rature and filament displacement are obtained at (7 to 8)x10¹² cm^-3 plasma concentration under ohmic heatina conditions. While operating with pUlsed gas injection, the plasma confinement, near the point shifted inside by 1 to 1.5 cm, favours attaining operating modes at a higher concentration. At approximately 3 to 4 cm displacements the impurity level growth is observed

[en] The Thomson scattering has been used to determine the density and temperature of an inhomogeneous nonstationary plasma. A common method to calibrate the Thomson scattering device consists in replacing the plasma by a gas and measuring the Rayleigh scattering cross section. The angular distribution of the scattered light in Argon is measured, the incident light is a ruby laser with Δt = 30ns and lambda = 6943nm and vertically polarized. We have found that angular distribution is strongly favored in the forward direction (30⁰, 45⁰, 60⁰) and defavored for backward direction (90⁰, 120⁰, 135⁰, 150⁰) in agreement with the results of George, et al, but in disagreement with the Rayleigh theory which assumes a uniform distribution. Our results may be related to the form of the scattered light spectrum which undergoes a dramatic change through the kinetic-hydrodynamic transition. The general form of the spectrum is determined by the parameter y = 1/Kl (where K = 4π sin (theta/2)/lambda, theta is the scattering angle and l is the free path path), which increases in the direction of the hydrodynamic regime (small angles). By analogy, the Thomson scattering presents the same aspects with α = 1/Klambda /SUB D/ (where lambda /SUB D/ is the Debye length). The deviation from the uniform distribution provides the possibility to determine the plasma turbulence spectrum from the scattered light

[en] A time-resolving spectrograph has been used to survey the forbidden magnetic dipole emissions of titanium, vanadium, chromium, iron, and nickel ions injected into the TFR (Tokamak de Fontenay-aux-Roses) plasma. A number of magnetic dipole transitions within the n = 2 ground configuration of the isoelectronic sequences from FI to BI were identified in the tokamak spectra; in some cases, experimental values of the wavelength were measured for the first time. The spectrograph had a photoelectric multispectral detector and a calibrated linear photometric sensitivity; thus, reliable determinations of the brightnesses in typical tokamak discharges could be made for these lines

[en] The Tokamak Fusion Test Reactor (TFTR) being built at Princeton Plasma Physics Laboratory is the largest such facility in the U.S. and places tremendous demands on the instrumentation in general and remote positioning equipment in particular. The Universal Diagnostic Probe System is a mechanism that inserts several types of scientific plasma measuring instruments into the plasma edge of the Fusion Reactor. It operates below the reactor substructure and makes a reliable and accurate insertion approximately 4.5 meters vertically from the stowed position. Provision is also made for rotating the instrumentation at the probe head and its 16 electrical conductors (2 of which are high voltage) 360 degrees at a varying rate, when in the fully extended or stowed position. This system is exposed to harsh environments of temperature (in excess of 200⁰C), high vacuum (less than 10^-9 Torr), high radiation levels (4 x 10⁵ rad (SI)), and high magnetic impulses (150 Tesla/sec), without outgassing contaminants to the fusion plasma

[en] The Advanced Stellarator WENDELSTEIN VII-AS is an upgraded version of the existing W VII-A Stellarator at Garching, Germany. Optimized field configuration, modular coil set, improved access for external heating, and increased plasma radius are the main properties of the new device. The aim of this experiment is to investigate a net current free plasma in an Advanced Stellarator configuration produced by various external heating methods (neutral beam injection, electron and ion cyclotron heating). This paper presents a survey of the design features and characteristic data of the newly designed Stellarator experiment W VII-AS and gives some more detailed information on the stress calculation of the nonplanar coils in the modular field system, the manufacturing process of such coils, as well as on the calculation, design and fabrication of the unconventionally shaped modular vacuum vessel, its ports and flanges, and on the assembly of the whole machine. An overview will also be given on the external heating equipment. Finally, a prospect of further Stellarator development will complete this paper

[en] The population distributions over the rotational levels of excited electronic-vibrational states of the hydrogen molecule were obtained in low-pressure plasma of capillary arc discharge by measuring certain emission band intensities. It is shown that simple excitation models (based on assumptions of the direct electron impact excitation and on the independence of the effective mean lifetime of the excited molecules on the rotational quantum number) are applicable fairly well in the investigated plasma. In particular, the values of the gas temperature given by different bands coincide within the experimental errors. Therefore, it is possible to determine the gas temperature in these non-equilibrium conditions with an acceptable accuracy (better than 5-7%). (author)

No abstract available

[en] Using 80 miniature soft-X-ray detectors viewing along chords through a plasma cross-section at one toroidal location, tomographic reconstructions of emissivity have been obtained without the need for assuming any symmetry or rotation of the plasma. In one class of plasma discharges, it is found that a large m=1 oscillation, which previously had been ascribed to the rotation of an MHD instability, actually is not rotating at all. (author)