An advanced Thomson scattering system has been built for a linear plasma generator for plasma surface interaction studies. The Thomson scattering system is based on a Nd:YAG laser operating at the second harmonic and a detection branch featuring a high etendue (f /3) transmission grating spectrometer equipped with an intensified charged coupled device camera. The system is able to measure electron density (n e ) and temperature (T e ) profiles close to the output of the plasma source and, at a distance of 1.25 m, just in front of a target. The detection system enables to measure 50 spatial channels of about 2 mm each, along a laser chord of 95 mm. By summing a total of 30 laser pulses (0.6 J, 10 Hz), an observational error of 3% in n e and 6% in T e (at n e = 9.4 × 10 18 m −3 ) can be obtained. Single pulse Thomson scattering measurements can be performed with the same accuracy for n e > 2.8 × 10 20 m −3 . The minimum measurable density and temperature are n e < 1 × 10 17 m −3and T e < 0.07 eV, respectively. In addition, using the Rayleigh peak, superimposed on the Thomson scattered spectrum, the neutral density (n 0 ) of the plasma can be measured with an accuracy of 25% (at n 0 = 1 × 10 20 m −3 ). In this report, the performance of the Thomson scattering system will be shown along with unprecedented accurate Thomson-Rayleigh scattering measurements on a low-temperature argon plasma expansion into a low-pressure background.

Impurity transport in the T-10 tokamak plasma with ohmic heating is studied in this paper. The values of various impurities densities, measured with the use of passive spectral diagnostics in the visible (Z eff ), active charge exchange measurements (He, C, O), and integral bolometric measurements with absolute extreme ultraviolet detectors (Fe, W) are shown. The experimental data show that accumulation level is growing with impurity nuclear charge and determined by the parameter1.5 , which is common for all sorts of impurities. Accumulation process is determined by neoclassical processes and begins with the increase of impurity content in the plasma and ends with the formation of density profiles more peaked than the n e (r). In discharges with low γ anomalous transport completely dominates. So it prevents the impurity accumulation and flattens their density profiles down to the n e (r). These observations correlates with measured negative (positive) plasma potential in discharges with high γ (low γ). 1D modelling using ASTRA and STRAHL transport codes is performed to describe the behaviour of impurities in a wide range of T-10 ohmic regimes. It is shown that the coefficients of anomalous transport D an and V an established in Krupin et al (1983 Sov. J. Plasma Phys. 9 529-36) and Krupin et al (1985 12th EPS Conf. on Plasma Physics) by describing the density dynamics of injected argon and potassium ions are applicable for the modelling of the He, C, O, W impurity density profiles and their sources. The analysis of the obtained results allows us to state the existence of a common dependence of the anomalous transport for all ions (impurities and deuterons) on the discharge parameters in the T-10 ohmic regimes.

First experimental results of tungsten transport investigation in OH and ECRH plasmas in the T-10 tokamak with W-limiter and movable Li-limiter are presented. It is shown that tungsten tends to accumulate (a joint process of cumulation and peaking) near the plasma axis in ohmic regimes. The cumulation of W is enhanced in discharges with high values of the parameter that coincides with accumulation conditions of light and medium impurities in T-10 plasmas. Experiments with Li-limiter show the immeasurable level of Li3+ (0.3–0.5% of ne) of T-10 CXRS diagnostics because of the low inflow of Li with respect to other light impurities. Nevertheless, the strong influence of lithium on inflow of light and tungsten impurities is observed. In discharges with lithized walls, vanishing of light impurities occurs and values of are obtained. It is also shown that the tungsten density in the plasma center decreases by 15 to 20 times while the W inflow reduces only by 2 to 4 times. In lithized discharges with high γ, the flattening of the tungsten density profile occurs and its central concentration decreases up to 10 times during the on-axis ECRH. This effect is observed together with the increase of the W inflow by 3 to 4 times at the ECRH stage.

The charge exchange recombination spectroscopy (CXRS) diagnostics on the T-10 tokamak is described. The system is based on a diagnostic neutral beam and includes three high etendue spectrometers designed for the ITER edge CXRS system. A combined two-channel spectrometer is developed for simultaneous measurements of two beam-induced spectral lines using the same lines of sight. A basic element of the combined spectrometer is a transmitting holographic grating designed for the narrow spectral region 5291 ± 100 Å. The whole CXRS system provides simultaneous measurements of two CXRS impurity spectra and Hα beam line. Ion temperature measurements are routinely provided using the C(6+) CXRS spectral line 5291 Å. Simultaneous measurements of carbon densities and one more impurity (oxygen, helium, lithium etc.) are carried out. Two light collecting systems with 9 lines of sight in each system are used in the diagnostics. Spatial resolution is up to 2.5 cm and temporal resolution of 1 ms is defined by the diagnostic neutral beam diameter and pulse duration, respectively. Experimental results are shown to demonstrate a wide range of the CXRS diagnostic capabilities on T-10 for investigation of impurity transport processes in tokamak plasma. Developed diagnostics provides necessary experimental data for studying of plasma electric fields, heat and particle transport processes, and for investigation of geodesic acoustic modes.

We have shown that in spatial structures based on color centers created by electrons in a lithium fluoride crystal, the distances between centers reach 1.6 nm and 3.6 nm for F 1 and F 2 centers respectively. This suggests considerable potential opportunities for using electron technology to form structures in the crystals with spatial resolution of such an order of magnitude. We measured the decrease in fluorine content on the irradiated surface of the crystal. We found the concentrations of F 1 , F 2 , F 3 + , F 3 (R 2 ), and F 4 (N 1 ) centers. We established that the specific characteristics of color center formation by electrons leads to an increase in the efficiency of creation of F 3 and F 4 centers. We determined the decrease in the average luminescence lifetimes of F 2 and F 3 + centers as a result of concentration quenching. We observed distortion of the luminescence con- tour for F 2 centers as a result of absorption of its short-wavelength portion by other centers and emission of radiation by the latter in its long-wavelength portion.Introduction. Formation processes, properties, and characteristics of nanosized media and structures and also the prospects for development of nanotechnologies are quite timely problems which are widely studied today. In this paper, we study and discuss the possibilities for creating nanostructures in crystals when they are bombarded by electrons. Electron bombardment leads to formation of intrinsic radiation-induced color centers in crystals and crystalline films [1]. Color centers considerably alter the optical and other characteristics of crystals and films at the sites where they are located, which makes it possible to form certain structures by controlling the spatial distribution of centers. In [2,3], it is suggested that technologies based on creating color centers by an electron beam be used for fabrication of optics devices with high spatial resolution: photomask templates for microelectronics, waveguides, etc. A review of the first research steps in this direction is given in [4].The spatial resolution of elements in structures created by the indicated method is limited in principle by the sizes of the color centers and the linear resolution limits attainable in electron optics. The sizes of color centers are equal to a few interatomic distances in the crystal in which they are formed. Thus using color centers to form structures or record information makes it possible to achieve the highest possible spatial resolution, limited by the atomic structure of the solid. For example, the distance between adjacent atoms in lithium fluoride crystals (LiF), which we used to conduct all the experiments in this work, is 0.2 nm. Consequently, the size of a single element of the structure created by the color center is equal to ≈1 nm. This is much greater than the possibilities for all media for image recording known at this time.The limiting linear resolution in optics, including electron optics, is directly proportional to the wavelength of the radiation used. The de Broglie...