A regime with electron heat confinement improvement was recently found in the initial phase of discharges in the TUMAN-3M tokamak. An internal transport barrier (ITB) formation in this regime was confirmed by Thomson scattering measurements and by transport modelling. Two possible reasons for the ITB formation are discussed in the paper: by reduction of turbulent transport in the presence of low magnetic shear or by plasma sheared rotation. It is demonstrated that low magnetic shear formation is possible in the current ramp-up phase of the Ohmic discharge. The low magnetic shear does not seem to be the only reason for the transport reduction. Results of Doppler reflectometry measurements of poloidal rotation of density fluctuations are presented. It is found that core confinement improvement correlates with the appearance of sheared rotation of the density fluctuations and with a burst of the MHD activity. The ITB formation in the regime seems to be a result of a combined action of reduced magnetic shear and plasma sheared rotation.

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Phone: þ7 (812) 292 73 92, Fax: þ7 (812) 297 10 17 We report a new technique of amorphous metal nanoparticles fabrication based on generation of liquid metal microdrops, their charging in electron flux with subsequent drops fission. Fission of charged metal drop occurs when its charge exceeds a critical value given by Rayleigh instability condition. Nanosize droplets, resulted from fission, cool down at extremely high rate to produce amorphous metal nanoparticles. Initial metal microdrops are generated at the end of an anode tip exposed to strong electric field and electron flux focused to the tip. The emitted drops then enter an electron beam where they are charged up to instability and are involved in fission process. To eliminate secondary electron emission (SEE) which can prevent drop charging we used electron beams of low energy. With beam energy properly chosen, SEE coefficient is less then unity for all drop sizes and drop charging up to unstable state is ensured. Granular films consisting of amorphous copper particles 2 nm in size are fabricated by the described technique. The results of atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies of the fabricated films are presented. Possible applications of the fabricated structures related to their unusual properties are considered.

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