В эксперименте получены плазменно-пылевые облака из вещества метеорита Царев, имитатора лунного реголита LMS-1D и ильменитового концентрата с помощью микроволнового разряда в порошковых средах. Для каждого из образцов зарегистрирована динамика развития разряда и образования плазменно-пылевого облака с последующей релаксацией после окончания микроволнового импульса. По спектрам излучения плазмы и поверхности твердого тела определены температуры газа, электронов и поверхности. Проведенное сравнение фазового и элементного состава исходных образцов и образцов после воздействия плазмы показало, что существенного изменения состава не происходит. Однако результаты сканирующей электронной микроскопии четко указывают на сфероидизацию исходных угловатых частиц и частиц неправильной формы. Также наблюдается появление сферических частиц, размеры которых больше, чем линейные размеры частиц в исходном образце. Полученные результаты указывают на возможность использования таких экспериментов для исследования химических и плазмохимических процессов синтеза и модификации веществ в условиях плазменно-пылевых облаков, встречающихся в космических явлениях.

In the experiment, plasma–dust clouds were obtained from the substance of the Tsarev meteorite, a simulant of lunar regolith LMS-1D and ilmenite concentrate using a microwave discharge in powder media. For each of the samples, the dynamics of the development of the discharge and the formation of a plasma–dust cloud with subsequent relaxation after the end of the microwave pulse were recorded. From the emission spectra of the plasma and the surface of a solid body, the temperatures of the gas, electrons and surface were determined. A comparison of the phase and elemental composition of the initial samples and samples after exposure to plasma showed that there is no significant change in the composition. However, scanning electron microscopy results clearly indicate spheroidization of the original angular and irregularly shaped particles. The appearance of spherical particles is also observed, the dimensions of which are larger than the linear dimensions of the particles in the original sample. The results obtained indicate the possibility of using such experiments to study chemical and plasma-chemical processes of synthesis and modification of substances under conditions of plasma–dust clouds encountered in space phenomena.

Results are presented of the determination of the temperature of the surface of powders in experiments on plasma-chemical synthesis of micro- and nanosize structures in the mixtures of aluminum oxide Al2O3 and palladium Pd with different palladium concentrations. The obtained estimates of surface temperature (2400–3100 K) are between the melting and boiling points at atmospheric pressure of the components of the powder mixture Al2O3 and Pd, which creates suitable conditions for the ignition of self-sustained (chain) plasma-chemical reactions.

ИМПУЛЬСНО-ПЕРИОДИЧЕСКИЙ РЕЖИМ ЭЦР-НАГРЕВА ПЛАЗМЫ В СТЕЛЛАРАТОРЕ Л-2М

Impurity injection into plasma caused by the sputtering of the wall coating in the L-2M stellarator during auxiliary electron cyclotron resonance heating leads to a change in the level of plasma density fluctuations with frequencies above 0.25 MHz: suppression of long-wavelength (k ⊥ = 2 cm–1) density fluctuations in the edge plasma, intensification of short-wavelength (k ⊥ = 30 cm–1) and long-wavelength (k ⊥ = 1 cm–1) fluctuations at the midradius of the plasma column, and intensification of short-wavelength fluctuations (k ⊥ = 20 cm–1) in the plasma center (including the gyroresonance region). At the same time, the level of fluctuations with frequencies below 0.25 MHz remains unchanged. In the edge plasma, a decrease in the plasma potential and suppression of its fluctuations is observed during impurity injection, which also causes an increase in MHD activity.

The experiments on ECR plasma heating were carried out at the L-2M stellarator at very high volume power density (up to 3.0 MW/m3). Under these conditions, non-monotonous hollow density profiles were measured. At the maximum heating power of P = 0.75 MW, the concavity in the axial region becomes drastic ne(0)/nemax = 0.5. In these experiments, plasma temperature profiles measured in the axial plasma region r/ap < 0.4 occur to be rather flat. We have also measured two-slope SXR spectra in the range from 2 to 12 keV. The possible reasons for these observed phenomena were discussed. However, with growing ECRH power up to PECRH = 0.75 MW, we have not observed dramatic deterioration of plasma confinement at the L-2M stellarator. The measured energy lifetime is generally consistent with that determined from the international LHD scaling.

currentless plasma of the L-2M stellarator after switching-on of auxiliary ECR heating G.M. Batanov, M.S. M.S. Berezhetskii, V.D. Borzosekov, S.E. Grebenshchikov, I.A. Grishina, N.K. Kharchev, A.A. Kharchevskii, Yu.V. Khol’nov, L.V. Kolik, E.M. Konchekov, N.F. Larionova, A.A. Letunov, V.P. Logvinenko, D.V. Malakhov, A.I. Meshcheryakov, A.E. Petrov, K.A. Sarksyan, S.V. Shchepetov, N.N. Skvortsova, V.D. Stepakhin, I.Yu. Vafin, D.G. Vasilkov A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow

Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia, e-mail: meshch@fpl.gpi.ru 1. EXPERIMENTAL SETUP Experiments on plasma creation and heating by microwave radiation of high power density of PECRH/VP = (2.0 -4.0) MW/m -3 were carried out at the L-2M stellarator [1]. In these experiments, nonmaxwellian SXR spectra were measured. The L-2M device is a classical two-pole stellarator (l = 2, N = 7) with a major radius of R = 1 m, minor plasma radius of a = 0.115 m, and toroidal magnetic field of B0 = 1.34 T. The rotational transform varies from ι = 0.18 at the magnetic axis to ι = 0.78 at the plasma edge. A gyrotron with a power of up to 600 kW is used to create and heat plasma at the frequency 75 GHz (the second harmonic of the electron gyrofrequency). The resonance region was in the center of plasma. Microwaves were delivered to the plasma by the waveguide (k⊥B0). The section in which heating was performed was spaced at a distance of about 1 m from the section in which the SXR spectrometer was arranged. Spectral measurements were carried out by the SXR spectrometer which is capable of measuring spectra in the energy range from 1 to 80 keV and has the count rate of V = 1.7·10 5

Results are presented from L-2M stellarator experiments on testing a possible method for detection of water microleakages in the cooling system of the first wall and vacuum chamber of ITER. The method consists in the spectroscopic detection of spectral lines of the OH hydroxyl, which forms via the dissociation of water molecules in plasma. Emission in the spectral band of 305–310 nm can be detected even at water leakage rates less than 10 −4 Pa m 3 /s. Chemical reactions between water and boron compounds on the vacuum chamber wall delay the detection of leakages up to ∼2000 s. A similar phenomenon can be expected when a leakage will occur in ITER, where the materials suggested for the first wall (Be, Li) can also chemically react with water.

Results of testing of a possible method for location of water microleakages in the cooling system of the first wall and vacuum chamber of ITER are presented. The method consists in spectroscopic detection of the emission lines of atoms and ions of the Xe additive dissolved in water. These lines are excited when the water with dissolved Xe contacts the plasma. The high electron cyclotron resonance heating (ECRH) power deposited in a relatively small plasma volume in the L-2M stellarator ( P = 0.5 MW, V = 0.24 m 3 , and the specific heating power ∼2 MW/m 3 ) makes it possible to achieve plasma parameters close to those in the edge plasma of ITER for different operating modes, including the H-mode with an edge transport barrier. In test experiments, several lines of Xe ions were revealed suitable for detection of xenon in plasma with parameters close to those in the edge plasma of ITER at leakage rates at a level of ∼10 −6 Pa m 3 s −1 and spatial resolution of ∼0.5 cm.

ИЗМЕНЕНИЕ СОСТАВА И СТРУКТУРЫ БОРОУГЛЕРОДНОЙ ПЛЁНКИ В ПРОЦЕССЕ РАБОТЫ СТЕЛЛАРАТОРА Л-2МА.И.Мещеряков 1 , В.М.Шарапов 2 , В.П.Логвиненко 1 , А

Experimental results on boronization in plasma shots at the T-11M tokamak and stellarator L-2M are presented. Nontoxic and nonexplosive metacarborane C(2)H(12)B(10) was used in boron deposition process. Experiments at the tokamak have been carried out in shots with parameters: toroidal field similar to 1-1.2 T, plasma current I(p) = 70 kA, average shot duration t(p) similar to 150 ms and electron density along the central chord n(e) similar to 2.5 x 10(13) cm(-3). The impurities in wall areas have been suppressed. High vacuum characteristics of the discharge chamber were stabilized. Stabilization of a plasma filament has improved. Experiments at the stellarator have been carried out in ohmic heating discharges with parameters: plasma current I(p) = 18-20 kA, toroidal magnetic field B(o) = 1.25 T, averaged electron density n(e) = (1.0-1.2) 10(13) cm(-3), central electron temperature T(c) = 300 eV and shot duration t(p) = 30-40 ms. High repeatability of experimental results was achieved. The technology developed provides an opportunity for practical production of renewable boron-carbon coatings using plasma shots in large-scale tokamaks and stellarators. (C) 2011 Elsevier B.V. All rights reserved.

2011, вып. 2 Осаждение борокарбидных плёнок в омическом разряде стелларатора Л-2М с использованием карборана 65 УДК 661

A plasma confinement mode characterized by the formation of an edge transport barrier (ETB) was discovered in the L-2M stellarator after boronization of the vacuum vessel wall. The transition into this mode is accompanied by a jump in the electron temperature by 100–200 eV at the plasma edge and a sharp increase in the gradient of the electron temperature T e in this region. The threshold power for the transition into the ETB confinement mode with an increased electron temperature gradient is P thr ▿Te = (60 ± 15)n e [1019 m−3] kW. The formation of the ETB manifests itself also in a substantial change in the electron density profile. A density peak with a steep gradient at the outer side forms at the plasma edge. The threshold power for the transition into the ETB confinement mode corresponding to a substantial increase in the plasma density gradient near r = a is P thr ▿Te = (67 ± 9)n e [1019 m−3] kW, which agrees to within experimental error with the threshold power for the transition into the ETB confinement mode determined from the sharp increase in the gradient of the electron temperature T e . The value of P thr for the L-2M stellarator agrees to within 25% with that obtained from the tokamak scaling. In the ETB confinement mode, the plasma energy W and the energy confinement time τ E determined from diamagnetic measurements increase by 20–30% as compared to those obtained from the stellarator scaling for the confinement mode without an ETB. When the heating power increases by a factor of 2–3 above the threshold value, the effects related to improved energy confinement disappear.