In this paper, a solution on improving a wooden bending beam by means of prestressing in proposed. The load-bearing capacity of a prestressed wooden beam is calculated. It has been established that ...the load-bearing capacity of wooden beams, which are bent in the direction of loading and fixed in this position, grows as compared to the load-bearing capacity of straight beams at the same length and the same surface area and shape of their cross sections.
This work presents first results of observation of parametric decay instabilities (PDI) in plasma formation and current start-up experiments on the spherical tokamak Globus-M by radiofrequency (RF) ...waves without use of induction electric field. In these experiments RF power was used for plasma discharge, as well as for current ramp-up. The current direction was determined on the direction of vertical magnetic field. We used RF generator with operational frequency 900 MHz. Spectral analysis of electromagnetic radiation from plasma showed appearance of big number of low frequency oscillations which was excited by pump wave. These spectra are typical for non-linear parametric instabilities. PDI may lead to the redistribution of the incident RF power between secondary waves with frequencies, differing from pump, to abnormal reflection and even to significant change of plasma-wave interaction mechanism. PDI mostly appeared on the current ramp-up phase. Both sidebands with small shift and with large, about half of pump frequency shift were excited. Relation between PDI and discharge parameters was defined.
Data on the mineralogical composition of clay (<1 μm), fine silt (1–5 μm), medium silt (5–10 μm), and coarser (>10 μm) fractions of meadow solonchakous solonetzes (Calcic Gypsic Salic Stagnic ...Solonetz (Albic, Siltic, Columnic, Cutanic, Differentic)) developing from loesslike loam and clay in the North Crimean Lowland are presented. Fractions >5 μm constitute nearly 50% of the soil mass and are characterized by the same mineralogical composition in the entire profile; they consist of quartz, plagioclases, potassium feldspars, and micas (biotite and muscovite). The eluvial-illuvial redistribution of clay in the course of solonetzic process is accompanied by changes in the portion of mixed-layer minerals and hydromicas in the upper part of the profile; a larger part of the smectitic phase is transformed into the superdisperse state. In the eluvial SEL horizon and in the illuvial BSN horizon, the clay fraction is impoverished in smectitic phase and enriched in trioctahedral hydromicas. Upon calculation of the content of clay minerals per bulk soil mass, the distribution of mixed-layer minerals is either eluvial, or eluvial-illuvial, whereas the distribution of hydromicas has an illuvial pattern without distinct eluvial minimum in the SEL horizons. The eluvial-illuvial distribution pattern of clay minerals in solonetzes of the North Crimean Lowland is compared with the distribution pattern of clay minerals in solonetzes of the West Siberian Lowland. Coefficients characterizing differentiation of solonetzes by the contents of particular mineral components are suggested.
The Globus-M2 spherical tokamak is the considerably upgraded Globus-M facility. Its technical parameters were increased as much as possible to achieve the promising range of physical parameters ...(sub-fusion temperatures and collisionality of much less than unity). These parameters will be achieved in a compact magnetic configuration similar to that of the Globus-M tokamak, the plasma current and toroidal magnetic field amounting to 0.5 MA and 1 T, respectively. The demand to increase the magnetic field and plasma current in the Globus-M2 resulted in the need for a complete redesign of the electromagnetic system because the plasma equilibrium requirements have changed and the mechanical and thermal loads have considerably increased as compared to the Globus-M. The vacuum vessel and the in-vessel components of the new Globus-M2 tokamak remain the same. Power supplies were upgraded to provide the required currents in the toroidal field coil and the central solenoid. The Globus-M2 tokamak was build up and preliminary tests were carried out. New auxiliary heating systems and diagnostics were developed and installed to be used in future experiments. Fist plasma was achieved at the Globus-M2 in April 2018.
Experimental results on the generation and maintenance of the toroidal current in the Globus-M spherical tokamak by using waves in the lower hybrid frequency range without applying an inductive ...vortex electric field are presented. For this purpose, the original ridge guide antennas forming a field distribution similar to that produced by multiwaveguide grills were used. The high-frequency field (900 MHz) was used for both plasma generation and current drive. The magnitude of the generated current reached 21 kA, and its direction depended on the direction of the vertical magnetic field. Analysis of the experimental results indicates that the major fraction of the current is carried by the suprathermal electron beam.
Basic experimental results on cyclotron heating of the ion plasma component in the Globus-M spherical tokamak obtained by means of the ACORD-12 charge-exchange ion analyzer are presented. A procedure ...for determining the maximum energy of fast ions confined in the plasma is described. The procedure was applied to estimate the limiting energy of hydrogen minority ions accelerated during ion cyclotron heating in the Globus-M tokamak. The experimental evaluation of the maximum hydrogen ion energy is confirmed by simulations of ion orbits. Recommendations for optimizing experiments on ion cyclotron heating in the Globus-M tokamak are formulated.
Comparative results of experiments on the ion-cyclotron resonance (ICR) heating of plasma in the Globus-M spherical tokamak using a hydrogen-deuterium mixture are presented. The experimental data are ...analyzed over a long period of time during which the internal surface of the chamber walls was gradually coated with graphite plates. The observed monotonic decrease in the efficiency of ICR plasma heating in the chamber with increasing graphite coverage can be explained by a growth in the high-frequency power absorption in the coating material. Results of numerical simulation of this process are reported.
A conceptual design of the lower hybrid current drive (LHCD) system for the upgraded T-15 tokamak (RNC Kurchatov Institute, Moscow) is presented. A tentative theoretical analysis, including extensive ...numerical simulations of different antenna types and LH wave propagation as well as estimation of LHCD efficiency, is carried out. The analysis has shown the possibility of launching a 4-5 MW radio frequency power through one tokamak port and driving up to a 1 MA LH current at a plasma density of 2-3 × 10
13
cm
−3
. The most suitable design of the whole LHCD system and the antenna, in particular, is discussed as well as the main technical problems of the T-15 LHCD project.
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