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A multi-diagnostic study of the fast ion losses and redistribution during toroidal Alfvén eigenmodes at the Globus-M and Globus-M2 spherical tokamaks was performed. Mode amplitude and frequency evolution are discussed. Local energy-resolved spatial transport was examined using an active neutral particle analyzer. Losses and transport dependences on the mode amplitude were obtained. The change in the ion transport with the increase in plasma current and toroidal magnetic field is reported. The experimental data are compared with the modeling results. [ABSTRACT FROM AUTHOR]

Spatial and temporal structure of Alfvén waves was studied with array of magnetic probes in compact tokamak TUMAN-3M. Poloidal mode numbers have been determined for Alfven instabilities bursts of the two types: short and long ones. Absence of poloidal rotation of magnetic field perturbations was found for both types of bursts. Also, in both cases, no pronounced asymmetry of magnetic field perturbation in the direction of the major radius was detected. [ABSTRACT FROM AUTHOR]

The Alfvén oscillations have been studied in ohmically heated deuterium discharges with LH-transition in the TUMAN-3M tokamak in order to clarify their location in a plasma column. The Alfvén oscillation location was determined by comparison of the oscillation frequency measured with magnetic probes and that calculated from local density assuming the typical dispersion relation for Alfvén waves f = (2π)−1k||vA, where vA is the Alfvén velocity and k|| is the the parallel wave number in the direction of the magnetic field. It was found that they are localized in central part of plasma column inside r/a < 0.5 region. Candidate sets of mode numbers have been determined. [ABSTRACT FROM AUTHOR]

We have experimentally studied the influence of toroidal magnetic field ( B) and plasma current ( I) on the capture and confinement of energetic ions (EIs) formed upon ionization of a neutral beam injected in a tokamak. Based on the results of measurements of the flux of 2.45-MeV fusion neutrons, it is concluded that the amount of EIs significantly grows with increasing B from 0.7 to 1.0 T and Ip from 140 to 180 kA. In addition to the classical Coulomb slowing down, a supplementary channel of EI losses is found that accounts for a 15% decrease in their confinement time. [ABSTRACT FROM AUTHOR]

The influence of toroidal magnetic field on the energy confinement time τ in the ohmic H-mode has been studied in the TUMAN-3M tokamak with low magnetic field. The experiments were performed at a toroidal magnetic field of B = 0.68−1.0 T, which is about twice as large as that (0.25-0.5 T) studied in analogous experiments on the NSTX and MAST spherical tokamaks. The results are indicative of a strong dependence of the energy confinement time on toroidal magnetic field: τ ∝ B. This scaling is much stronger than that projected for the ITER (τ ∝ B), while being somewhat weaker than the scalings observed on the NSTX and MAST devices. The stronger (as compared to the ITER scaling) dependence of τ on B observed in these experiments should be taken into account in designing thermonuclear facilities with small aspect ratios and toroidal magnetic fields-in particular, fusion neutron sources. [ABSTRACT FROM AUTHOR]

In the tokamak, in which the winding generating the toroidal field with induction B is powered from an inductive energy storage, resistive losses are the main factor that causes B to decrease during a discharge. Upgrading of the power supply circuit of the toroidal magnetic field winding (TFW) in the TUMAN-3M tokamak is aimed, primarily, at increasing B in the injection heating phase and, second, at maintaining B quasi-stationarity during the whole tokamak discharge. To do this, an additional two-section capacitive storage commuted by two thyristor switches has been introduced into the available circuit. Either section of the storage is characterized by a charging voltage of 0.25 kV, a capacitance of 4.32 F, and an energy capacity of 135 kJ. The maximum discharge current of the section is 40 kA. The upgraded circuit compensates for the resistive loss in the TFW and ensures thereby a 50% increase in the magnetic field during injection heating relative to the old circuit: B = 1.0 T instead of 0.68 T. In this case, the circuit maintains a TFW current of 110 kA with an accuracy of 10% for ∼60 ms. [ABSTRACT FROM AUTHOR]

Differential circuits consisting of two series arrays of 10-junction parallel SQIFs were developed, designed and fabricated with 4.5 kA/cm^2 Nb HYPRES process. The differential voltage response evolution with applied magnetic field providing opposite frustration of the serial arrays was analysed in detail. Linear differential response with amplitude as high as 22 mV was observed for the serial arrays of 108 parallel SQIFs. It was shown that the response linearity is kept within some range of the applied frustrating magnetic field. [ABSTRACT FROM AUTHOR]

In the current paper a method of plasma position measurement, alternative to magnetic diagnostics, is proposed. The method is based on determination of the last closed flux surface (LCFS) location by detecting the maximum of electrostatic potential profile. The experiments were carried out on the TUMAN- 3M tokamak in a series of similar ohmic heating shots. The method proved effective in LCFS localization; it allowed calculation of corrections for magnetic diagnostics, used routinely for plasma position detection. This method can be used in limiter and divertor tokamaks for independent check and clarification of electromagnetic plasma position diagnostics. [ABSTRACT FROM AUTHOR]

A chain of parallel-connected Josephson elements described by a resistive model is considered as a model for high-temperature Josephson junctions. The calculated spectra of the Josephson generation can account for the experimentally observed subharmonic Sapiro steps on the current-voltage characteristic and for their aperiodic dependence on the external magnetic field. [ABSTRACT FROM AUTHOR]

The peculiarities of the heavy ion beam probe implementation on the small aspect ratio tokamak TUMAN-3M are analyzed. The toroidal displacement of beam trajectory due to the high Ipl/Btor ratio is taken into account when designing the layout of the diagnostic. Numerical calculation of beam trajectories using realistic configuration of TUMAN-3M magnetic fields and parabolic plasma current profile resulted in proper adjustment of probing and detection parameters (probing ion material, energy, entrance angles, detector location, and orientation). Secondary ion energy analyzer gain functions G and F were measured in situ using neutral hydrogen puffed in the tokamak vessel as a target for secondary ions production. The detector unit featured split-plate design and had additional electrodes for secondary electron emission suppression. As a result, the diagnostic is now capable of plasma potential evolution measurement and is sensitive enough to trace the potential profile evolution at the L-H mode transition. [ABSTRACT FROM AUTHOR]