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Pestchanyi S.,Karlsruhe Institute of Technology | Garkusha I.,Institute of Plasma Physics of Ukraine | Landman I.,Karlsruhe Institute of Technology
Fusion Engineering and Design | Year: 2010

Simulations of tungsten armour cracking under small ELM-like plasma heat load, which does not cause surface melting, have been performed using the PEGASUS-3D code. A dedicated series of experiments have been performed in the QSPA-Kh50 facility for measurements of the unknown tungsten thermo-physical properties and for verification of the PEGASUS-3D simulation results. The simulations revealed that a cellular crack network with average mesh size Δ ∼ 0.5 mm formed after first ELMs and the pattern does not change further. With increasing number of repetitive ELMs loads, the average crack width Δ(n) has a maximum value Δm. The ratio of Δm/Δ is equal to the tungsten thermal expansion at the maximum surface temperature. Δ(n) tends to this value exponentially. The number of ELMs nm needed for Δ stabilization depends on the ELMs energy density and time duration, nm ∼ 300 for the simulated ELMs of 0.45 MJ/m2 and 0.25 ms duration. The PEGASUS-3D code is prepared for simulations of tungsten armour damage under action of ELMs of various energy deposition and time duration. These parameters of ELMs depend on ITER regimes of operation and on how successful will be the efforts on ELMs mitigation. © 2010 Elsevier B.V. All rights reserved.


Pestchanyi S.,Karlsruhe Institute of Technology | Garkusha I.,Institute of Plasma Physics of Ukraine | Landman I.,Karlsruhe Institute of Technology
Fusion Engineering and Design | Year: 2011

Brittle destruction of tungsten armour under action of edge localised modes of plasma instabilities (ELMs) in ITER is an important issue determining the lifetime of the divertor. Besides, cracking of the armour produces tungsten dust with characteristic size of 1-10 μm flying from the armour surface with velocities up to 10 m/s. Influx of the tungsten dust into the ITER confinement decreases the temperature of the plasma, reduces the thermonuclear gain and even may run the confinement into disruption. This paper describes experiments in QSPA-Kh50 plasma gun and modeling, which has been performed for providing more insight into the physics of tungsten cracking under action of ELMs and for confirmation of the important result on stabilization of the crack development at the tungsten armour surface, predicted in our previous paper - the same authors, 2010. The threshold value of energy density deposition for start of tungsten cracking has been measured as 0.3 MJ/m2 after 5-10 shots. From analytical considerations three times smaller threshold value has been predicted with increasing number of shots. © 2011 Elsevier B.V. All rights reserved.


Pavlichenko R.O.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2014

A new electron cyclotron emission antenna was designed to be installed outside of Uragan-3M vacuum tank. The system will be utilizing different diagnostic port to minimize the length of the output microwave beam. Its design is based on Gaussian beam optics and consists of two plane and two concave mirrors. The concave mirror surfaces are defined using the concept of elliptical surface, where the origin of emission and outside detection antenna coincide with foci of ellipsoid. The new electron cyclotron emission antenna will be installed for a 2015 experiment to measure the electron temperature profile and its fluctuations. This paper reports the general design of the new quasi-optical antenna system. © 2014, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Dreval M.B.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2014

A miniature pinhole camera array for spatially and temporally resolved measurements of soft X-ray emission has been designed and installed in the URAGAN-3M torsatron. Two features of the U-3M: a) very large vacuum vessel; b) a quite high RF noise from the 8-9 MHz plasma heating generators, form a rather difficult for the SXR system design conditions. In order to increase the SXR brightness in 25-50 times the pinhole camera is placed between helical coils near plasma in the “A-A” cross-section. The size of the pinhole and its location relative to the diode array are optimized to cover the whole poloidal cross section and to achieve a good spatial resolution with minimum overlap in nearby channels. Possible misalignments of the SXR system can cause errors in the line of sight impact parameter less than 30 (similar to the SXR channel viewing angle). The maximum of the measured SXR brightness intensity corresponds to the central channel № 11 of the system. The 2.5 107 V/A SXR photodiode photocurrent amplifiers with additional RF noise suppress electronics have been manufactured. The SXR electronics does successfully work in high vacuum conditions near the plasma. Time evolution of the SXR emission profile and its fluctuations are successfully measuring by the designed diagnostics. © 2014, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Kotenko V.G.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2014

In numerical calculations for the model of combined magnetic system a possibility of existence of closed magnetic surfaces is shown. The model comprises the magnetic system of l=2 torsatron without additional toroidal magnetic field coils (heliotron) with a single current-carrying turn as an element of the mirror-type magnetic system. The turn encircles the heliotron closed magnetic surface region and produces a magnetic field of opposite direction to the heliotron magnetic field. © 2014, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Pavlov S.S.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2015

On the base of the numerical model, taking into account the strong transverse and longitudinal dispersion of plasma, the absorption and dispersion of the Fast Mode of fast magnetosonic wave (FW) near ICR harmonics ω = nωci at the quasiperpendicular propagation regime were investigated. It was shown that in the region of small longitudinal refractive index values N║ there appears the additional absorption that provides the value of optical thickness τ being constant in the entire region of additional absorption. At first and second harmonics the additional absorption can be interesting for FW plasma heating in the reactor-size devices. For higher harmonics it can be important for HF diagnostic purposes and for investigation of astrophysical plasmas. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Dreval M.B.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2015

A miniature pinhole camera array for spatially and temporally resolved measurements of soft X-ray plasma emission has been recently installed on the U-3M. The diagnostics has been tested in different types of the U-3M discharge. In low density frame antenna discharges with so-called “H-like” transition a fast SXR emission profile modification is observed. A phase shift of the SXR perturbation induced by the transition as well as different shapes of the perturbation is observed in different channels. The transition can be associated with MHD instability. Different shapes of the SXR emission profile has been observed in different discharge conditions. The SXR array is en excelent tool for study different types of the MHD activity. Different types of the low frequency MHD activity have been observed in the U-3M torsatron. The recently installed SXR diagnostics opens opportunity of detailed studies of the MHD activity together with its driver–the plasma pressure gradient. In the paper we are presented recent experimental results obtained with the use of SXP, without deep analysis these experiments. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Yeliseyev Y.N.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2015

The low-frequency spectrum of axially-symmetric modes of oscillations of the nonneutral plasma completely filling a waveguide is evaluated. Plasma consists of cold electrons and a small additive of ions produced by ioniza-tion of neutrals of background gas by electron impact. Ions are described by the equilibrium distribution function adequately taking into account the peculiarity of their formation. The spectrum of oscillations consists of the family of lower hybrid modes and families of "modified" of ion cyclotron (MIC) modes. MIC modes intersecting lower hybrid modes are unstable within a wide range of changing of fields and plasma density due to anisotropy of the ion distribution function. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Rudakov V.A.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2015

The spatial distributions of plasma parameters in the stellarators LHD and U-2M, operating under recycling conditions with the assumption of neoclassical transport realization, are calculated using the one-dimensional space-time numerical code. The stable solutions of the system of equations for the spatial distributions of ion and electron temperatures, plasma and neutral neutron density and ambipolar electric field are obtained. The flat spots formation in the radial profiles of plasma parameters near the plasma boundary is shown. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.


Pavlichenko R.O.,Institute of Plasma Physics of Ukraine
Problems of Atomic Science and Technology | Year: 2015

Electron cyclotron emission (ECE) diagnostic (superheterodyne millimeter wave radiometer) is a regular tool to provide the radial distribution and time dependence for a bulk electron population for the Uragan-3M (U-3M) plasmas. Under some plasma conditions when RF heating pulse switched off a substantial increasing of the radiation intensity signal we observed at the frequencies which corresponds to the second and third harmonics of ECE (2ωce, 3ωce) of the extraordinary mode. The existing phenomena could be attributed with the presence of the suprathermal (ST) and/or “runaway” electrons (RE) in U-3M plasmas. A procedure is described by which the electron temperature profile can be obtained from spectral measurements of the cyclotron emission at optically thin frequencies. No absolute calibration of the detection equipment is needed for this method. © 2015, National Science Center, Kharkov Institute of Physics and Technology. All rights reserved.

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