Laser diagnostics of plasma relative to about-wall range of tokamaks

The research is concerned with an about-wallplasma and a surface contacting with it. As a result, sections and lengths of waves for several lines of the spontaneous rotational combination scattering spectrum in hydrogen have been calculated for the second harmonic of the neodymium laser. The parameters of an electronic plasma component of the TW-1 tokamak have been determined by a method of Tomson scattering of the second harmonic of the neodymium laser; a selective coefficient of iron spraying by means of helium ions has been defined in conditions of a charge with a hollow cathode by a method of laser induced fluorescence. The interaction of a laser flare with target surface has been investigated by means of a laser proection microscope. Firstly it has been discovered, that a microrelief is formed after finishing of a laser impulseAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Hydrogen isotope ratios measurements by Penning gauge spectroscopy of molecular Fulcher-α band

Penning gauge spectroscopy of Balmer-α lines of hydrogen isotopes is widely used in fusion experiments to determine the hydrogen isotope ratios and the partial pressures in the pump duct. The Balmer-α line isotopic shifts are very small < 0.176 nm and the lines partially overlap because of the presence of energetic atoms produced by molecular dissociation. The ro-vibrational emission bands of each hydrogen isotopomer consist of many narrow spectral lines, covering a wide wavelength span and have an unique signature. To investigate the capability of the hydrogen molecular spectroscopy for the isotopic ratio determination, an Alcatel-type Penning gauge was coupled by the optical fiber to the Echelle spectrometer having 365–715 nm spectral range and the spectral resolving power above 20,000. The intensities of both atomic Balmer-α lines and molecular Fulcher-α bands were measured in the range of 6·10−6 – 4·10-3 mbar. The rotational and vibrational populations were almost independent of the gas pressure below 2·10-4 mbar. The total intensities of the Fulcher-α molecular bands were linearly proportional to the gas pressure. The H2 and D2 molecular emission in 599–639 nm spectral range were in a good agreement with the isotopic composition of the used gas mixtures

NEUTRON RADIATION DAMAGE IN CCD CAMERAS AT JOINT EUROPEAN TORUS (JET)

The neutron and gamma radiations in large fusion reactors are responsible for damage to charged couple device (CCD) cameras deployed for applied diagnostics. Based on the ASTM guide E722-09, the ‘equivalent 1 MeV neutron fluence in silicon’ was calculated for a set of CCD cameras at the Joint European Torus. Such evaluations would be useful to good practice in the operation of the video systems

Short-term retention in metallic PFCs: modelling in view of mass spectrometry and LIBS

Based on the conventional model of hydrogen retention in plasma-facing components, the question of hydrogen outgassing during and after plasma exposure is addressed in relation to mass spectrometry and laser-induced breakdown sprectroscopy (LIBS) measurements. Fundamental differences in retention and release data acquired by LIBS and by mass spectrometry are described analytically and by modelling. Reaction-diffusion simulations are presented that demonstrate possible thermal outgassing effects caused by LIBS. Advantages and limitations of LIBS as a tool for analysis of short term retention are discussed

Improving accuracy of Penning gauge spectroscopy for the determination of hydrogen isotope H/D ratios

Atomic spectral lines emitted from a Penning discharge are often used to quantify partial pressures and isotopes ratios in gases. To identify the potential of this method for thermal desorption studies, the hydrogen emission spectrum lines (Hα and Dα) were examined by an Alcatel Penning gauge. The hydrogen/deuterium pressures were measured by both a capacitive vacuum gauge and the Penning gauge. Different gas mixtures were produced by varying of hydrogen/deuterium flows. The Balmer-alpha lines intensities were recorded with help of a high etendue spectrometer coupled to the Penning gauge using relay optics together with fiber bundle and equipped with Peltier cooled CCD camera. Subsequent measurements using hydrogen and deuterium gases revealed for identical pressures in the range of 10−6–10−3 mbar that the Hα line intensities are systematically higher the Dα line intensities by a factor of 1.28 ± 0.01. This observation can be explained by the dissociative excitation of the molecular hydrogen by electron impact. In addition the Hα line intensity for the H2 gas having constant partial pressure is slightly increased with total gas mixture pressure. Taking into account of both effects essentially improves the accuracy of the determination of partial pressures and isotope H/D ratios