Zonal flows and their high-frequency counterpart, the geodesic acoustic modes (GAMs) are considered as a possible mechanism of the plasma turbulence self-regulation. In the T-10 tokamak GAMs have been studied by the heavy ion beam probing and multipin Langmuir probes. The wide range of the regimes with Ohmic, on-axis and off-axis electron cyclotron resonance heating (ECRH) were studied (B t = 1.5-2.4 T, I p = 140-300 kA, ne = (0.6-6.0) × 10 19 m −3 , P EC < 1.2 MW). It was shown that GAM has radially homogeneous structure and poloidal m = 0 for potential perturbations. The local theory predicts that f GAM ∼ √ T /m i /R, that means the frequency increases with the decrease of the minor radius. In contrast, the radial distribution of experimental frequency of the plasma potential and density oscillations, associated to GAM, is almost uniform over the whole plasma radius, suggesting the features of the nonlocal (global) eigenmodes. The GAM amplitude in the plasma potential also tends to be uniform along the radius. GAMs are more pronounced during ECRH, when the typical frequencies are seen in the narrow band from 22 to 27 kHz for the main peak and 25-30 kHz for the higher frequency satellite. GAM characteristics and the range of GAM existence are presented as functions of T e , density, magnetic field and P EC .

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.

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Зонды Ленгмюра являются одной из наиболее используемых диагностик, позволяют проводить измерения средних значений и флуктуаций параметров периферийной плазмы: электронной температуры и концентрации, потоков частиц, потенциала, элек-трических полей, изучать турбулентный перенос частиц. В работе исследовано поведение данных параметров в пристеночной области плазмы токамака Т-10. Вблизи последней замкнутой поверхности (LCFS) наблюдается формирование перемежаемой турбулентности, относительный уровень флуктуаций возрастает с увеличением радиуса. Радиальное электрическое поле E r имеет положительный знак в области плазмы, находящейся за диафрагмой (SOL), вблизи LCFS меняет знак. Скорость полои-дального вращения плазмы и скорость E×B-дрейфа в SOL составляют 0,5-1,5 км/с и направлены в сторону ионного диамаг-нитного дрейфа. В периферийной плазме наблюдаются колебания ГАМ-типа (12-18 кГц). Частота колебаний растёт с увели-чением электронной температуры T e , что совпадает с предсказаниями теории ГАМ-осцилляций.Ключевые слова: токамак Т-10, зонды Ленгмюра, турбулентность. INVESTIGATIONS OF THE PERIPHERAL PLASMA BY LANGMUIR PROBES ON THE T-10 TOKAMAK R.Yu. Solomatin, S.A. Grashin NRC «Kurchatov Institute», Moscow, RussiaLangmuir probes are one of the most used diagnostics that allow us to take measurements of mean and fluctuated parameters of the peripheral plasma such as the electron temperature and concentration, particle flux, plasma potential, electric fields, to study the turbulent particle transport. The work represents investigations of these parameters' behavior in the peripheral plasma of T-10 tokamak. Near the LCFS is observed the formation of intermittent turbulence, the relative level of fluctuations rises with the radius. Radial electric field E r is positive in the SOL and changes its sign near the LCFS. The poloidal plasma rotation velocity and the E×B drift velocity in the SOL are close to each other in value 0.5-1.5 km/s and directed towards the ion diamagnetic drift. In the peripheral plasma the GeodesicAcoustic-Mode-like (GAM) oscillations were observed (12-18 kHz). The frequency of oscillations rises with the electron temperature T e , according to the theoretical predictions for GAM-oscillations. ВВЕДЕНИЕВ экспериментах на существующих термоядерных установках (токамаках, стеллараторах и др.) пе-риферийная плазма играет важнейшую роль и во многом определяет процессы в центральной плазме. Особый интерес при этом вызывает исследование взаимодействия плазмы с элементами первой стенки в термоядерных установках, вызывающего загрязнение плазмы поступающими со стенки примесями, что, в свою очередь, влияет на удержание частиц и энергии в основной плазме.Зонды Ленгмюра являются одной из наиболее используемых диагностик периферийной плазмы в то-камаках, так как это простой и недорогой способ измерения как средних значений, так и флуктуаций па-раметров периферийной плазмы: электронная температура и концентрация, потоки частиц, потенциал, электрическое поле и число Маха. Более того, именно эта диагностика позволяе...

Abstract. Fast-scale plasma perturbations (0.5-2 MHz) are studied during disruption instability in the T-10 tokamak. A system of movable magnetic probes is used to measure magnetic field perturbations in the plasma periphery. Spatial distribution of soft X-ray oscillations is measured using silicon surface-barrier detectors. A possible connection between the fast-scale electromagnetic and X-ray oscillations and arc discharges in the plasma edge near localization of the MHD modes during plasma disruption is considered.