High Current Generator Research Articles

Plasma high-current generator of wideband high-power microwaves with magnetic self-insulation

A plasma maser that does not use a strong magnetic field for transporting a relativistic highcurrent electron flow is calculated within the particle-in-cell model. Tuning of the average radiation frequency from 3 to 7GHz with a single pulse spectrum width of 2 to 3GHz is demonstrated. The power of a radiation pulse with a duration up to 70 ns is from 0.5 to 0.7GW at the efficiency of 4 to 6%.

Implosion dynamics of a megampere wire-array Z-pinch with an inner low-density foam shell at the Angara-5-1 facility

The implosion dynamics of a pinch with a highly inhomogeneous initial axial distribution of the load mass was studied experimentally. A cascade array consisting of a double nested tungsten wire array and a coaxial inner cylindrical shell located symmetrically with respect to the high-voltage electrodes was used as a load of the Angara-5-1 high-current generator. The cylindrical foam shell was half as long as the cathode− anode gap, and its diameter was equal to the diameter of the inner wire array. It is shown experimentally that two stages are typical of the implosion dynamics of such a load: the formation of two separate pinches formed as a result of implosion of the wire array near the cathode and anode and the subsequent implosion of the central part of the load containing the cylindrical foam shell. The conditions are determined at which the implosion of the central part of the pinch with the foam cylinder is preceded by intense irradiation of the foam with the soft X-ray (SXR) emission generated by the near-electrode pinches and converting it into the plasma state. Using such a load, which models the main elements of the scheme of a dynamic hohlraum for inertial confinement fusion, it is possible to increase the efficiency of interaction between the outer accelerated plasma sheath and the inner foam shell by preionizing the foam with the SXR emission of the near-electrode pinches.

Study of composition of the ultrafine material produced from graphite–catalyst mixture under extreme energy action

Ultrafine materials were produced under conditions of extreme energy effects on the mixture of graphite and Ni-Mn catalysts. For the purpose to obtain various forms of carbon, including diamond-like forms, experiments were performed on a MIG high-current generator with the current amplitude of 2-2.5 MA and current rise time of 100 ns. The composition of the explosion products was studied using x-ray diffraction and x-ray phase analyses, the impedance spectroscopy, optical and scanning electron microscopy, x-ray microanalysis and energy dispersive x-ray analysis and the laser confocal Raman microscopy. It was found that the carbon in the studied materials is in the graphite, diamond-like (the faceted particles or agglomerates of faceted particles in size about or less than 250 nm) and amorphous forms.

Hard X-ray source based on low-impedance rod pinch diode

The results of experiments on the formation of a low-impedance diode in a rod pinch diode configuration preliminarily short-circuited by a radial foil have been described. The low-impedance diode is formed as a result of detachment of the foil (accelerated by the current of a high-current generator) from the anode rod. It has been shown that, by changing the shape of the anode tip, the thickness of the aluminum foil, and its position relative to the anode tip as by reconnecting the current via the foil and rod plasma, it is possible to obtain from one to several sequential hard X-ray pulses.

Behavior specificities of the plasma in the REB - polymeric anode interactions.

To study Relativistic Electron Beam (REB) interaction with a set of polymeric targets we have made experiments for the investigation of the plasma dynamics in high-voltage diode of high-current generator. It is necessary for applied goals, such as correction of mathematical models of high power density deposition in the matter, for testing materials reaction under the powerful impulse of ionizing radiation, etc. An electron-optical streak camera (EOC) was used to measure the velocity of the visible light border of the plasma glowing. It was estimated to be from 10 to 35 km/s at the energy-release density in range of 200 - 800 J/cm2. In a few of experiments, besides regular motion of contrast border in the direction from electrodes to the middle of the diode, the motion from the middle to the periphery of the high-voltage diode with velocity up to 500 km/s was observed. It was by an order of magnitude greater than regular one.

The effect of biofilm thickness on electrochemical activity of Geobacter sulfurreducens

It is widely believed that the high electrochemical performance of Geobacter sulfurreducens relies on its thick and conductive biofilms in bioelectrochemical systems. However, in this study, the G. sulfurreducens biofilm reached the highest electrochemical activity with a biofilm thickness of ∼20 μm, and then the electrochemical activity decreased with increasing thickness until the biofilm growth ceased at a thickness of ∼45 μm. The electrochemical analysis and the metabolic spatial variability showed that in the first 5 cycles the live cells grew fast, which led to a rapid drop of charge transfer resistance and further contributed to high current generation, however, from cycle 5 to 12, a great many inactive cells accumulated in the inner layer of biofilm, which resulted in high diffusion resistance. Thus, although the G. sulfurreducens can always form thick biofilms, its highest electrochemical activity reached at a much thinner thickness, suggesting that the live-cell mass rather than the biofilm thickness is responsible for the high current generation.

A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments.

A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10(-2) Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak current of new generators can be increased to 5-6 MA and about 100 GPa ramp stress can be produced on the metallic samples for high pressure physics, and a conceptual design of CQ-5-MMAF was given.

Skin electric explosion in double-layer conductors with a low-conductivity deposited layer

The experiments on explosion of cylindrical conductors aimed at comparison of plasma formation during skin explosion of homogeneous and double-layer conductors with an external layer with a lower conductivity are carried out on a high-current MIG generator (current amplitude up to 2.5 MA and current rise time 100 ns). The generator is loaded with cylindrical copper conductors with a diameter of 3 mm on the cathode part of which a titanium layer of thickness 20, 50, and 80 μm is deposited in vacuum. This type of loading makes it possible to compare the behaviors of the homogeneous and double-layer conductors in identical conditions. It is shown that using the double-layer structure of the conductor with an external layer of thickness 20–80 μm with a lower conductivity, which is obtained by vacuum arc deposition, higher values of magnetic induction (as compared to homogeneous conductor) can be attained on its surface prior to plasma formation and spread.

Demanding response time requirements on coherent receivers due to fast polarization rotations caused by lightning events.

Lightning events can cause fast polarization rotations and phase changes in optical transmission fibers due to strong electrical currents and magnetic fields. Whereas these are unlikely to affect legacy transmission systems with direct detection, different mechanisms have to be considered in systems with local oscillator based coherent receivers and digital signal processing. A theoretical analysis reveals that lightning events can result in polarization rotations with speeds as fast as a few hundred kRad/s. We discuss possible mechanisms how such lightning events can affect coherent receivers with digital signal processing. In experimental investigations with a high current pulse generator and transponder prototypes, we observed post FEC errors after polarization rotation events which can be expected from lightning strikes.

Underwater Electrical Explosion of Wires and Wire Arrays and Generation of Converging Shock Waves

A brief review of the results obtained in recent research of underwater electrical explosions of wires and wire arrays using microsecond-, submicrosecond-, and nanosecond-timescale high-current generators is presented. In a microsecond-timescale wire explosion, good agreement was attained between the results of experiments and the results of magnetohydrodynamic calculations coupled with equations of state (EOS) and modern conductivity models. Conversely, in a nanosecond-timescale wire explosion, the wire resistance and the EOS were modified in order to fit experimental data. In experiments with cylindrical and spherical wire arrays, generation of a converging shock wave (SW) was demonstrated allowing formation of an extreme state of water in the vicinity of either the axis or the origin of the SW’s implosion. In addition, it is shown that SW convergence in superspherical geometry allows one to achieve larger values of pressure, density, and temperature of water in the vicinity of the axis of convergence than in the case of a spherical implosion. The results of experiments and numerical analysis showed that a cylindrical SW keeps its symmetry along the main path of its convergence. In addition, it is shown that underwater electrical explosion of an X-pinch wire configuration and a cone wire array allows one to generate fast jets of metal and water, respectively, without using chemical explosions.

Mobile Electric-Discharge Blasting Unit for Splitting off and Destruction of Rocks and Concrete

The article describes the pulse power system for electric-discharge blasting of rocks and concrete, the main equipment of which is a high current pulse generator with operating voltage up to 15 kV. The test of short-circuit experiment was produced, the main parameters of the discharge circuit L = 1.01 μH, R = 9 mΩ were calculated. Based on the results of the experiments the impedance Z = 42.5 mΩ of discharge circuit was defined. The pulse power system with mentioned parameters has maximum power condition deviation of about 8.6 %.

Preparation of Fe-doped deuterated polyethylene loads for the angara 5-1 high-current generator

A new method of manufacturing low-density foamed deuterated polyethylene cylinders (20–200 mg/cm3) with a diameter of 1–2 mm and length of 10 mm is designed. Up to 5 wt % Fe dopants can be embedded into the foam for diagnostic analysis. Polyolefine-based microcellular foams are produced by dissolving polymers at high temperatures in aromatic hydrocarbon, subsequently initiating phase separation in a solution (usually during fast cooling) and gel formation. It has been determined that for obtaining high-quality products it is necessary to preliminary cool the system down to 135°C. To avoid wasteful polymer losses, the whole process is carried out in the single ampoule and multiple centrifugation is used for mixing. A solvent is removed using critical-point drying.

Nonlinear diffusion waves in high magnetic fields

The nonlinear diffusion of a magnetic field and the large-scale instabilities arising upon an electrical explosion of conductors in a superstrong (2-3 MG) magnetic field were investigated experimentally on the MIG high-current generator (up to 2.5 peak current, 100 ns current rise time). It was observed that in the nonlinear stage of the process, the wavelength of thermal instabilities (striations) increased with a rate of 1.5-3 km/s.

Shock wave convergence in water with parabolic wall boundaries

The convergence of shock waves in water, where the cross section of the boundaries between which the shock wave propagates is either straight or parabolic, was studied. The shock wave was generated by underwater electrical explosions of planar Cu wire arrays using a high-current generator with a peak output current of ∼45 kA and rise time of ∼80 ns. The boundaries of the walls between which the shock wave propagates were symmetric along the z axis, which is defined by the direction of the exploding wires. It was shown that with walls having a parabolic cross section, the shock waves converge faster and the pressure in the vicinity of the line of convergence, calculated by two-dimensional hydrodynamic simulations coupled with the equations of state of water and copper, is also larger.

Methods of high current magnetic field generator for transcranial magnetic stimulation application

This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR

ENWEndNote BIBJabRef, Mendeley RISPapers, Reference Manager, RefWorks, Zotero AMA Yermakova T. MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR. Health Problems of Civilization. 2015;9(3):20-23. doi:10.5114/hpc.2015.57129. APA Yermakova, T. (2015). MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR. Health Problems of Civilization, 9(3), 20-23. https://doi.org/10.5114/hpc.2015.57129 Chicago Yermakova, Tetyana. 2015. "MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR". Health Problems of Civilization 9 (3): 20-23. doi:10.5114/hpc.2015.57129. Harvard Yermakova, T. (2015). MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR. Health Problems of Civilization, 9(3), pp.20-23. https://doi.org/10.5114/hpc.2015.57129 MLA Yermakova, Tetyana. "MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR." Health Problems of Civilization, vol. 9, no. 3, 2015, pp. 20-23. doi:10.5114/hpc.2015.57129. Vancouver Yermakova T. MORPHOLOGIC CHANGES IN THE NODULAR GOITRE INDUCED BY THE LIGASURE HIGH FREQUENCY CURRENT GENERATOR. Health Problems of Civilization. 2015;9(3):20-23. doi:10.5114/hpc.2015.57129.

Electrically exploded opening switches in high-current explosive magnetic generators

This paper presents a review of publications on the use of electrically exploded foil opening switches to form current pulses up to 100 MA (up to 45 MA in experiments) with a rise time of 0.1–10.0 µs. Physical schemes and models are considered, and the efficiency of foil opening switches for existing and advanced facilities is analyzed.

Электровзрывные размыкатели сильноточных взрывомагнитных генераторов

Электровзрывные размыкатели сильноточных взрывомагнитных генераторов

Temporal response of silicon EUV and soft X-ray detectors

A small-sized generator of picosecond electron beams is used to measure the temporal resolution of EUV and soft X-ray silicon detectors produced by the Ioffe Physical Technical Institute, Russian Academy of Sciences. The temporal resolution of the EUV and soft X-ray detectors based on silicon photodiodes is shown to be ∼1 ns. Preliminary experiments have been performed using these detectors with the aim of investigating the radiation characteristics of a soft X-ray source based on an X-pinch driven by a small-sized highcurrent generator with a current pulse amplitude of 250 kA. This source is used at the Institute of High Current Electronics for soft X-ray backlighting diagnostics of various plasmas.

High-Current Magnetic Field Generator for Transcranial Magnetic Stimulation Applications

This paper describes a novel approach to designing a high-current magnetic field generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. Challenges for robust and practical design are introduced. A few of the main possible solutions for designing versatile and powerful pulses are introduced and discussed. Finally, future improvement in functionality of the HCMFG is proposed.