Sergey V. Loginov

Decimeter-band frequency-tunable sources of high-power microwave pulses

This article describes S-band sources of high-power microwave (HPM) pulses: a resonant backward wave oscillator (BWO) producing ∼5-GW, 100-J pulses, based on the SINUS-7 electron accelerator, and a double-section vircator with a peak power of ∼1 GW and a pulse width of 20-50 ns, powered from either the SINUS-7 accelerator or the MARINA inductive-store pulse driver with a fuse opening switch.

Primary energy storages based on linear transformer stages

Primary storages based on a linear transformer scheme were developed long ago. In this scheme, the secondary turn only has to be insulated from the high output voltage. Seven years ago at the High Current Electronics Institute (HCEI) a primary storage based on a linear transformer scheme and called the Linear Transformer Driver (LTD) stage was designed. In LTD stages, the primary turn, the storage capacitors with the switches, the core, and the outer conductor of the secondary turn are integrated into the stage cavity representing one separate building block of the primary storage. The body of the LTD cavity keeps ground potential during the shot allowing us to assemble them in series or in parallel depending on load requirements. Such flexibility of the storage structure and high output power of the LTD stages allows us to replace for some applications the traditional water line technology with LTD-based primary storages that are connected directly to the load (Direct Drive Scheme-DDS). In this article, we present the design of several LTD stages developed at HCEI and give examples of high-power energy storages produced by using the LTD technology.

S-band vircator with electron beam premodulation based on compact pulse driver with inductive energy storage

This paper describes an S-band vircator system with electron beam premodulation, built on the base of the MARINA compact high-voltage pulser with inductive energy storage. The peak microwave output was /spl sim/1 GW with /spl sim/5% power efficiency and 50-ns full-width at half-maximum. The microwave frequency was constant during the pulse as determined by the resonator. Substantial spontaneous shortening of the microwave pulse was observed. Possible mechanisms for this phenomenon are discussed and supported by three-dimensional KARAT simulations.

Plasma and Magnetic-Field Dynamics in Conduction Phase of Opening Switch

Self-consistent plasma and magnetic-field dynamics in the plasma-opening-switch conduction phase is considered within the framework of 1-D single-fluid magnetohydrodynamics. The profiles of plasma-flow parameters and magnetic field in the switch current channel, depending on plasma conductivity, are obtained. An analytical solution for the magnetic-field profile in the current channel is presented. The energy partition in the current channel is calculated. The issue of plasma conductivity during the magnetic-field pulse is discussed.

Plasma Dynamics in Opening Switches

The energy balance of a plasma opening switch in the conduction stage is calculated, in which the dominant process is magnetic field penetration into the plasma volume due to the magnetic piston effect. This mechanism is typical for a microsecond plasma opening switch of the mega-ampere range. It is also shown that the process of magnetic field penetration into the switch plasma is determined by the field diffusion near the magnetic piston, followed by the convective transport of magnetic field in the plasma. This transport is due to the field being frozen-in into the plasma flow behind the shock wavefront, which is formed in the plasma accelerated by the magnetic field pressure. The shock wave propagation leads to the formation of directed plasma flow with falling density, velocity, and pressure in the region between the magnetic piston and the shock wavefront. The following analysis of gas dynamics and related electromagnetic problems reveals the most important processes determining plasma and magnetic field dynamics.

A Vacuum Feedthrough Insulator at a Voltage of ∼1 MV

The design and results of tests of a vacuum feedthrough insulator for a pulsed electron accelerator with a voltage of ∼1 MV, a current of ∼20 kA, and a half-height voltage-pulse duration of ≥ 400 ns are presented. A method for distributing the voltage over the sections of the insulator due to an electron emission from specially created surfaces is proposed.

Electron Loss in Microsecond Megaampere Plasma Opening Switches

This paper discusses the efficiency of energy transfer from an inductive energy store to a short-circuit load with a microsecond megaampere plasma opening switch (POS). A very simple electrotechnical technique for estimation of electron current loss is proposed, and its operability is proven. The applicability of the technique for analysis of experimental data is considered. The low rate of rise of the POS resistance along with considerable current loss causes weak pulse sharpening with a time shift of the current pulse and a decrease in its magnitude.

Plasma Opening Switch Operation Scenario

The regularities of current conduction and opening in microsecond megaampere plasma opening switches are considered. Switch conduction current scaling is determined by plasma pushing by magnetic field pressure and is compared with experimental results. Current channel structure is conditioned by diffusion and convective magnetic field transport into the accelerated plasma flow. An analytical solution for the magnetic field profile in the current channel is presented. Based on experimental results, the dependence of switch voltage on switch parameters is presented. Switch reclosure limits the energy output efficiency from an inductive storage into load.

Power Flow in the POS-to-Load Transition Region

This paper provides analysis of experiments aimed at defining the capabilities of plasma opening switch (POS) for energy transfer to a load of inductance comparable with the inductance of the energy store vacuum section. The analysis is performed using the substantiated technique that allows quantitative estimation of the POS efficiency. Under the same conditions with a conduction current of ~1 MA and POS voltage of ~1 MV, the energy transferred to the load depends strongly on the transmission line design. When the electrode gap in the line is ~1 cm, the energy delivered to the load is ~40 kJ. Increasing the gap to ~4-cm increases this energy to ~100 kJ.

High-energy wide-aperture lasers pumped by radially convergent electron beams

The results of the experimental study of UV and IR lasers pumped by electron beams are presented. The accelerators with radially convergent electron beam for pumping gas mixtures under pressure up to 3 atm were used. Laser radiation energies of up to 2 kJ, 200 J, 100 J, 50 J have been obtained at the wavelengths of 308 nm, ~2.8 μm, 250 nm and 1.73 μm, 2.03 μm, correspondingly.