Thomson scattering diagnostic systems in the ITER divertor

A diagnostic array has been developed for studying the operating modes of the divertor in the ITER tokamak-reactor using the Thomson scattering technique. The aim of this study is to measure the spatial profiles of the electron temperature and density. The structure of the diagnostic setup was selected on the basis of a classical diagnostic geometry and the high-resolution LIDAR system, which provide access to different regions of the divertor plasma. A severe radiation environment, limited access to the plasma in the ITER divertor, and a high-dust environment (the divertor plate erosion material) in the divertor volume pose many problems for performing diagnostics under unique conditions having no analogs in the tokamaks that are now in operation. Different methods for protecting optical surfaces from plasma-enriched deposition are proposed and analyzed. The efficiency of these methods has been demonstrated in bench tests. The concept of laser and detector systems and diffraction polychromators capable of operating at different electron temperatures with a lower limit of 1 eV, has been justified and approved.     

Developing an edge-plasma diagnostic tool for the Globus-M tokamak based on measuring ratios of HeI lines

A diagnostic technique that is based on measuring the ratios of neutral-helium line strengths has been developed for peripheral distributions of electron temperature and density of tokamak plasma. The main components of the technique are a four-channel filter-lens imaging polychromator (FLIP-4) and a Phantom Miro M110 high-speed camera for recording the images. The polychromator has been assembled, adjusted, and tested on an optical test bench. The optical system was installed on the spherical Globus-M tokamak. Some preliminary experiments were carried out. Images of the plasma-gun jet were obtained at neutralhelium lines.     

Heat and Particle Transport in the Initial Phase of Ohmic Discharges in the Globus-M Spherical Tokamak

Technical Physics Letters - The results of experiments and simulations of the transport of heat and particles in the Globus-M spherical tokamak are presented. Investigations were carried out in the...     

Studying the interaction of high-energy deuterons with plasma in the Globus-M spherical tokamak

Plasma parameters in the Globus-M spherical tokamak have been measured upon injection of a deuteron beam with energy about 30 keV and a power of up to 700 kW. Dependences of the ion temperature and neutron yield on the plasma current and density and the gap width between the wall and plasma are considered. Possible characteristics of fast-ion confinement in the modified Globus-M2 tokamak are discussed.     

The Effect of Low-Frequency Magnetohydrodynamic Modes on the Development of Filaments in the Globus-M Tokamak

Technical Physics Letters - Experimental data are presented that indicate the effect of the magnetohydrodynamic tearing mode in the Globus-M spherical tokamak on the occurrence of filamentary...     

Application of resonant Raman scattering of light for plasma diagnostics

An application of a diagnostics method based on the scattering of laser radiation by atoms in plasma is discussed. The high sensitivity of the method is due to resonant enhancement of the Raman scattering cross section with a small offset from the exact optical resonance with an intermediate level. The measurements of the spatial distribution of the excited argon atoms were performed in the plasma of a high-frequency induction discharge in a wide range of offsets from exact resonance under the conditions of linearity and with saturation of the scattering intensity. The results of the experiments are used to analyze the sensitivity of the method and to formulate the requirements for diagnostics so as to optimize the experimental conditions. Pis’ma Zh. Tekh. Fiz. 25, 46–54 (September 26, 1999)     

Testing of intracavity multipass probing systems for diagnostics of a tokamak plasma by laser photoionization

Efficient laser systems for plasma probing have been developed using stable cavity configurations with low diffraction losses to improve the sensitivity of photoionization diagnostics. These probing systems were tested in demonstration experiments using the FT-1 tokamak. The results indicate that reliable measurements of the neutral hydrogen density may be made in the range 10⁸–10⁹ cm³ in a tokamak plasma. Pis’ma Zh. Tekh. Fiz. 25, 60–65 (February 12, 1999)     

Observation of filaments on the globus-M tokamak by Doppler reflectometry

Experimental results showing evidence for the development of filaments in plasma of the Globus-M spherical tokamak have been obtained by the method of Doppler reflectometry. The correlation between the reflectometric data and results of probe measurements at the periphery of discharge in the tokamak is found. Experimental data were used to determine the rotation velocities of filaments, the moments of their appearance at the transition to improved confinement, and regions of filament formation.     

Observation of geodesic acoustic modes in the Globus-M spherical Tokamak

The first results of an investigation of geodesic acoustic modes (GAMs) in the Globus-M spherical tokamak are presented. The experiments were performed using Doppler reflectometry. The conditions of the appearance of GAMs, the nature of their development, and their radial localization have been studied. The obtained data are compared to experimental results obtained in tokamaks with large aspect ratios.     

Development of laser methods for diagnosing the surface state of the walls of the discharge chambers in tokamak facilities

A method for diagnosing plasma-induced coating deposited on the walls of the discharge chambers in tokamak facilities is described. This method is based on the atomization of the laser-ablated thin layer of the material deposited on the wall and the determination of the amount of the evaporated substance and its elemental composition proceeding from the luminescence intensity of reference lines in the laser-ablated plasma. Experiments performed on a test bench have demonstrated the main characteristics of this technique and limits of its applicability.