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Main parameters of the possible system of electron cyclotron resonance heating of the plasma for the compact tokamak with strong magnetic field (TRT) are presented. Preliminary estimates show that, to deposit radiation with calculated power of 10 MW into the plasma at pulse duration of 100 s, 12 1-MW gyrotron complexes will be required that operate at a frequency of 230 GHz. Preliminary calculations of the main components of the system are presented. [ABSTRACT FROM AUTHOR]

The influence of the magnetic-field profile in the gyrotron interaction space on the generation efficiency and frequency was experimentally studied. A profiled magnetic field was created by a system of several low-inductance coils. It is shown that it is possible to increase the generation efficiency by ~1.3 times, which is comparable with the results that are obtained using single-stage recuperation of the residual electron-beam energy. In this case, the proposed method is easier to implement and can be used jointly with the recuperation. It is also demonstrated that it is possible to control the generation frequency within a range of at least twice the width of the radiation spectrum with characteristic times of the order of milliseconds. This allows one to believe that the gyrotron frequency-stabilization circuit can be successfully performed using small changes in the magnetic field. [ABSTRACT FROM AUTHOR]

The electron cyclotron resonance heating (ECRH) system of the ASDEX Upgrade tokomak has been upgraded over the last 15 years from a 2MW, 2 s, 140 GHz system to an 8MW, 10 s, dual frequency system (105/140 GHz). The power exceeds the L/H power threshold by at least a factor of two, even for high densities, and roughly equals the installed ion cyclotron range of frequencies power. The power of both wave heating systems together (>10MW in the plasma) is about half of the available neutral beam injection (NBI) power, allowing significant variations of torque input, of the shape of the heating profile and of Qe/Qi, even at high heating power. For applications at a low magnetic field an X3-heating scheme is routinely in use. Such a scenario is now also forseen for ITER to study the first H-modes at one third of the full field. This versatile system allows one to address important issues fundamental to a fusion reactor: H-mode operation with dominant electron heating, accessing low collisionalities in full metal devices (also related to suppression of edge localized modes with resonant magnetic perturbations), influence of Te/Ti and rotational shear on transport, and dependence of impurity accumulation on heating profiles. Experiments on all these subjects have been carried out over the last few years and will be presented in this contribution. The adjustable localized current drive capability of ECRH allows dedicated variations of the shape of the q-profile and the study of their influence on non-inductive tokamak operation (so far at q95 > 5.3). The ultimate goal of these experiments is to use the experimental findings to refine theoretical models such that they allow a reliable design of operational schemes for reactor size devices. In this respect, recent studies comparing a quasi-linear approach (TGLF) with fully non-linear modeling (GENE) of non-inductive high-beta plasmas will be reported. [ABSTRACT FROM AUTHOR]

Based on a time-domain model, we demonstrate that a periodic train of powerful ultrashort microwave pulses can be generated in an electron oscillator consisting of two coupled helically corrugated gyrotron travelling wave tubes (gyro-TWTs) operating in regimes of amplification and saturable absorption, respectively. The mechanism of pulse formation in such an oscillator is based on the effect of passive mode-locking widely used in laser physics. Saturable absorption can be implemented in a gyro-TWT in the Kompfner dip regime by a proper matching of the guiding magnetic field. According to simulations with the parameters of an experimentally realized Ka-band gyro-TWT, the peak power of generated pulses with a duration of 200 ps can achieve 400 kW. [ABSTRACT FROM AUTHOR]

The state of the art for terahertz gyrotrons that are needed for various scientific research and practical applications is presented. Powers of 5 kW and 200 kW are obtained at frequencies of 1 and 0.7 THz using pulsed gyrotrons with pulse durations of tens of microseconds. A power of 100 W is demonstrated for cw gyrotrons at frequencies ranging from 0.2 to 0.5 THz. [ABSTRACT FROM AUTHOR]

We have developed the concept and design of a collector with a static nonadiabatic magnetic field, which allow one to exclude the influence of pulsed thermal loads and accumulation of nonelastic deformations in the collector body, as well as achieve the nearly uniform distribution of the heat release power density over its surface for an energy load of about 500 W/cm. Such a collector is characterized by moderate criticality with respect to variations in the electron energy distribution and the effect of an external scattering magnetic field. The decrease in criticality is achieved by choosing the cylindrical shape of the collector and using two pairs of counter-wound low-power solenoids in the collector system. [ABSTRACT FROM AUTHOR]

Viscous fluid flow in the space between a spherical and an ellipsoidal surfaces rotating with different angular velocities was studied. The conditions of the occurrence and features of radial fluid flows are discussed. The results can be used to study a number of geophysical phenomena related to the dynamics of the flow of fluid. [ABSTRACT FROM AUTHOR]

This paper is devoted to the theoretical analysis of Talbot effects in a curved square waveguide. A remote steering antenna as an important application of Talbot effects is considered. It is shown that the wavebeam repetition is considerably spoiled by the curvature even for bending angles about 5° if the steering plane coincides with the bending plane. However, high-efficient repetition exists at certain launching angles. If the wavebeam steering plane is perpendicular to the waveguide bending plane, high-efficient repetition takes place in a broad band of launching angles in the waveguide of the optimized rectangular cross-section. [ABSTRACT FROM AUTHOR]

It is shown that a rotating body containing a permanent magnet may be in stable noncontact equilibrium when placed in the field of a stationary magnet. It is assumed that the magnets are of a cylindrical shape and their magnetizations are aligned with the cylinder axis. The field of the magnets is simulated by two turns with direct current, which makes it possible to analytically find the forces and force moments acting on the movable magnet subjected to the field of the stationary one. Instability of the equilibrium state of a suspended body when its weight is counterbalanced by the repulsive force exerted by a stationary magnet follows from the Earnshaw theorem. It is demonstrated here that such instability may be removed with gyroscopic forces due to rotation of the suspended body. It turns out that the rotation of the movable magnet may stabilize not only its unstable angular but also translational degrees of freedom, which is a newly discovered effect. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]