Dynamo and Electrical Jet in Hall Plasmas, Application to Astrophysics

The magnetic field in Hall plasmas is frozen in the electron component and is advected not only with the plasma motion but also with the electrical current flow. Its coupling with the plasma may be not as strong as characteristic of the MHD approximation. The rotation and slipping of the magnetic field result in a very different and less efficient magnetic field generation by dynamo - rotating plasma disk in magnetic field. We found a some exact analytical solutions of nonlinear equations describing the dynamo. In particular, the dynamo may not dissipate the energy in the steady state limit. The 3-component magnetic field and magnetic energy are generated and accumulated during the transition time only. An electrical jet is the other unusual phenomenon for MHD. It was investigated theoretically and experimentally for laboratory plasmas during the last 15 years and now is used for fast current switching. We found periodical or shock-like nonlinear wave traveling along a Hall plasma column and not associated with plasma motion. A nonlinear equation describing a possible steady state magnetic field distribution and current flow in Hall plasma conductor is derived that differs from the Grad-Shafranov equation for the low pressure MHD plasma. In conclusion we discuss application of our results to astrophysical plasmas. This physics could be important for understanding the evolution of dusty plasma disks and jets around new stars.Comment: PDF, 8 pages with 1 figure, found stabilizing term for magneto-rotational instabilit

Mirror instability in a plasma with cold gyrating dust particles

In this work linear stability analysis of a magnetized dusty plasma with an anisotropic dust component having transversal motions much stronger than motions parallel to the external magnetic field, and isotropic light plasma components is described. Such a situation presumably establishes in a shock compressed space dusty plasma downstream the shock front. Oblique low-frequency magneto-hydrodynamic waves ($\omega\ll \omega_{cd}$, $\omega_{cd}$ being the dust cyclotron frequency) are shown to be undergone to the mirror instability. Consequences for nonthermal dust destruction behind shock fronts in the interstellar medium are discussed.Comment: 13 pages, 5 figs, accepted to Phys. Pasma

Characterization of the initial filamentation of a relativistic electron beam passing through a plasma

The linear instability that induces a relativistic electron beam passing through a return plasma current to filament transversely is often related to some filamentation mode with wave vector normal to the beam or confused with Weibel modes. We show that these modes may not be relevant in this matter and identify the most unstable mode on the two-stream/filamentation branch as the main trigger for filamentation. This sets both the characteristic transverse and longitudinal filamentation scales in the non-resistive initial stage.Comment: 4 page, 3 figures, to appear in PR

Terahertz Spectroscopy System of Gas Mixtures Based on a Solid State Superconducting Source and a Terahertz Receiver

Abstract: The application of a Josephson generator of the terahertz range based on a long superconductor–insulator–superconductor tunnel junction matched with a transmitting antenna and emitting a signal into open space is demonstrated for gas spectroscopy. The generator is used as an active source, the signal of which is absorbed by a sample of a gas mixture in a cell with a length of 60 cm and then recorded by a spectrometer based on a superconductor–insulator–superconductor receiver with a spectral resolution better than 100 kHz. In the experiment, the absorption lines of ammonia and water in the terahertz range were recorded, and the dependence of the spectral characteristics of the absorption lines on the pressure of the gas mixture in a wide range (from 0.005 to 10 mbar) was demonstrated

Experimental Signatures of Critically Balanced Turbulence in MAST

Beam Emission Spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, the particle (ion) streaming time along the magnetic field and the magnetic drift time are consistently comparable, suggesting a "critically balanced" turbulence determined by the local equilibrium. The resulting scalings of the poloidal and radial correlation lengths are derived and tested. The nonlinear time inferred from the density fluctuations is longer than the other times; its ratio to the correlation time scales as $\nu_{*i}^{-0.8\pm0.1}$, where $\nu_{*i}=$ ion collision rate/streaming rate. This is consistent with turbulent decorrelation being controlled by a zonal component, invisible to the BES, with an amplitude exceeding the drift waves' by $\sim \nu_{*i}^{-0.8}$.Comment: 6 pages, 4 figures, submitted to PR

An Antenna with a Feeder for a Superconducting Terahertz Josephson Oscillator with Phase Locking

A principal layout of a Josephson terahertz radiation oscillator integrated with a transmitting antenna-lens system and a harmonic mixer (HM) for phase locking of radiation has been proposed and was successfully implemented. Two antenna-feeder systems designed for the central frequencies of 0.3 and 0.6 THz and located on the same chip with the oscillator are numerically simulated and fabricated. A microstrip transmission line between the oscillator and the antenna is used as the feeder. A study was carried out on matching the oscillator power and HM for two designs; the frequency range of pumping HM was 0.25-0.45 and 0.5-0.68 THz for the designs at 0.3 and 0.6 THz, respectively. Good agreement was obtained between experimental results and numerical simulations. A study of the spectral characteristics of the radiation of the oscillator into the external space for the 0.6 THz design using a superconducting integrated spectrometer was carried out. The linewidth of an emission line in free-running regime was of the order of several megahertz; in the phase locking regime down to tens of kilohertz with a signal-to-noise ratio of more than 20 dB was obtained

ТРЕХЭЛЕКТРОДНЫЙ ВОЗДУШНЫЙ КОММУТАТОР С ГРАФИТОВЫМИ ЭЛЕКТРОДАМИ КВТГ-50 НА НАПРЯЖЕНИЕ ДО ±50 КВ И ИМПУЛЬСНЫЙ ТОК АМПЛИТУДОЙ ДО ±220 КА

Purpose. Development and creation of the simplified construction of a high-voltage heavy-current air three-electrode switchboard with graphite electrodes, intended for operation in composition the powerful generator of large impulsive current of artificial of linear lightning. Methodology. Electrophysics bases of technique of high-voltage and scientific and technical bases of planning of devices of high-voltage impulsive technique. Results. Developed and made a new construction of a high-voltage heavy-current air three-electrode switchboard with the graphite electrodes of KATG-50 on nominal voltage ±50 kV. This construction of switchboard KATG-50 has been passed experimental approbation in composition the heavy-current bit chain of powerful high-voltage generator of the аperiodic impulses of current of artificial linear lightning rationed on operating foreign standards with amplitude of Im=±(200±20) кА at their duration τP=(350±35) μs at level 0,5∙Im. Originality. First in domestic practice of development and creation of high-voltage heavy-current switchboards for the generators of large impulse currents of artificial lightning the ground of necessity of the use for their basic and managing electrodes of electrical engineering graphite is carried out. Practical value. The developed and made high-voltage heavy-current switchboard of cascade-tray KATG-50 from application in its composition of graphite electrodes possesses an enhanceable working resource and enhanceable stability of wearing-out at the use of similar switchboard in the bit chain of powerful pulsed current of the imitated linear lightning.Представлены основные технические характеристики и краткое описание конструкции высоковольтного трехэлектродного сильноточного воздушного коммутатора с графитовыми электродами КВТГ-50 на номинальное напряжение ±50 кВ. Созданный образец коммутатора предназначен для работы в разрядной цепи мощного высоковольтного генератора нормированных микросекундных импульсов тока искусственной молнии с амплитудой Im=±(200±20) кА при их длительности τp=(350±35) мкс на уровне 0,5∙Im. Данный коммутатор каскадного типа из-за применения графитовых электродов обладает повышенным рабочим ресурсом и повышенной стабильностью срабатывания при его использовании в составе генератора тока имитированной линейной молнии.Представлені основні технічні характеристики і короткий опис конструкції високовольтного трьохелектродного сильнострумового повітряного комутатора з графітовими електродами КВТГ-50 на номінальну напругу ±50 кВ. Створений зразок комутатора призначений для роботи в розрядному колі потужного високовольтного генератора нормованих мікросекундних імпульсів струму штучної блискавки з амплітудою Im=±(200±20) кА при їх тривалості τp=(350±35) мкс на рівні 0,5∙Im. Даний комутатор каскадного типу із-за застосування графітових електродів володіє підвищеним робочим ресурсом і підвищеною стабільністю спрацьовування при його використанні у складі генератора струму імітованої лінійної блискавки

THREE-ELECTRODE AIR SWITCHBOARD WITH THE GRAPHITE ELECTRODES OF KATG-50 ON VOLTAGE TO ±50 KV AND IMPULSE CURRENT BY AMPLITUDE TO ±220 KA

Purpose. Development and creation of the simplified construction of a high-voltage heavy-current air three-electrode switchboard with graphite electrodes, intended for operation in composition the powerful generator of large impulsive current of artificial of linear lightning. Methodology. Electrophysics bases of technique of high-voltage and scientific and technical bases of planning of devices of high-voltage impulsive technique. Results. Developed and made a new construction of a high-voltage heavy-current air three-electrode switchboard with the graphite electrodes of KATG-50 on nominal voltage ±50 kV. This construction of switchboard KATG-50 has been passed experimental approbation in composition the heavy-current bit chain of powerful high-voltage generator of the аperiodic impulses of current of artificial linear lightning rationed on operating foreign standards with amplitude of Im=±(200±20) кА at their duration τP=(350±35) μs at level 0,5∙Im. Originality. First in domestic practice of development and creation of high-voltage heavy-current switchboards for the generators of large impulse currents of artificial lightning the ground of necessity of the use for their basic and managing electrodes of electrical engineering graphite is carried out. Practical value. The developed and made high-voltage heavy-current switchboard of cascade-tray KATG-50 from application in its composition of graphite electrodes possesses an enhanceable working resource and enhanceable stability of wearing-out at the use of similar switchboard in the bit chain of powerful pulsed current of the imitated linear lightning.Представлены основные технические характеристики и краткое описание конструкции высоковольтного трехэлектродного сильноточного воздушного коммутатора с графитовыми электродами КВТГ-50 на номинальное напряжение ±50 кВ. Созданный образец коммутатора предназначен для работы в разрядной цепи мощного высоковольтного генератора нормированных микросекундных импульсов тока искусственной молнии с амплитудой Im=±(200±20) кА при их длительности τp=(350±35) мкс на уровне 0,5∙Im. Данный коммутатор каскадного типа из-за применения графитовых электродов обладает повышенным рабочим ресурсом и повышенной стабильностью срабатывания при его использовании в составе генератора тока имитированной линейной молнии.Представлені основні технічні характеристики і короткий опис конструкції високовольтного трьохелектродного сильнострумового повітряного комутатора з графітовими електродами КВТГ-50 на номінальну напругу ±50 кВ. Створений зразок комутатора призначений для роботи в розрядному колі потужного високовольтного генератора нормованих мікросекундних імпульсів струму штучної блискавки з амплітудою Im=±(200±20) кА при їх тривалості τp=(350±35) мкс на рівні 0,5∙Im. Даний комутатор каскадного типу із-за застосування графітових електродів володіє підвищеним робочим ресурсом і підвищеною стабільністю спрацьовування при його використанні у складі генератора струму імітованої лінійної блискавки

Gyrokinetic simulations of microinstabilities in stellarator geometry

A computational study of microinstabilities in general geometry is presented. The ion gyrokinetic is solved as an initial value problem. The advantage of this approach is the accurate treatment of some important kinetic effects. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally-efficient systematic study of the impact of the magnetic structure on microinstabilities