B. M. Kovalchuk

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.

Development of the ultra-fast LTD stage

The technology of the fast LTD stages is proposed for 1 MV driver with the goal to get a 60 ns pulse width at 80 % of peak voltage in the diode. For this driver a new LTD-100R stage is designed consisting of 20 GA 35389 capacitors. A 1 MV driver will include 7 such stages in series and provide 1 MV, 125 kA pulse in a critically matched load. The footprint of the whole system is ∼1.75 m2. The report includes the design of the new stage and results of the tests.

Capacitor units with air insulation for linear transformers

The design of two capacitor units intended for use in high-power pulsed generators is described and the results of their tests are presented. Each unit is an assembly consisting of a multichannel spark gap and two capacitors with a total capacitance of 80 or 16 nF and a charging voltage of up to 100 kV. The use of air at atmospheric pressure as the insulating and working medium of the spark gap is a feature of the capacitor units. The following parameters of the output pulses were obtained at a resistive load for the 80- and 16-nF units: currents of ∼48 and ∼20 kA, voltages of ∼55 and ∼52 kV, and times of energy deposition into the load of ∼140 and ∼60 ns, respectively. A model for numerical calculation of the transient discharge process in the capacitor units is presented and the influence of the capacitance of the capacitors and the number of spark channels in the spark gap on the parameters of the generated pulse is analyzed.

Development of a hybrid (solid state/gas) femtosecond laser system of multiterawatt peak power

Terawatt hybrid laser (THL-100) system on the basis of Ti:sapphire starting complex and final amplifier with gaseous optically driven active media on XeF(C-A) molecules is presented. Laser system is built at Institute of High Current Electronics SB RAS, Tomsk, Russia. It consists of Ti:sapphire starting complex and photochemical XeF(C-A) amplifier. The active media of amplifier pumped by VUV radiation has 24 cm aperture and 110 cm length. The results of numerical modeling of the output parameters and first experimental results are presented in this paper.

Development of a 100-terawatt hybrid femtosecond laser system

Terawatt hybrid (solid state/gas) laser (THL-100) system on the basis of Ti:sapphire starting complex (50 fs, 5 mJ) and photochemical XeF(C-A) amplifier with the aperture of 24 cm is presented. Laser system is built at Institute of High Current Electronics SD RAS, Tomsk, Russia. The design and peculiarities of optical pumping of XeF(C-A) amplifier, methods of pump power measuring, gain distribution across the active volume are discussed. The results of numerical modeling of the output parameters simulation are presented and one compared with first experimental results.

A four-channel source of high-power pulses of ultrawideband radiation

A source of nanosecond ultrawideband radiation is described. Four output bipolar pulses from the source can be synchronized with an rms deviation of less than 100 ps in the time of the voltage passage through zero or delayed by the moment of this passage in some pulse formers relative to other ones by a time of up to 300 ps using the pressure control in two-electrode discharge switches. At a 3-ns bipolar-pulse length, the obtained values of the effective potential of radiation at a pulse repetition rate of 100 Hz were 400 kV. The possibility of the wave-beam steering within limits of 12° was demonstrated.

Linear transformer accelerator for the excimer laser

A high-current accelerator for pumping of the 200-L excimer laser is developed, providing electron energy of 550 keV, a diode current of 320 kA, and an e-beam current of 250 kA. The high-voltage part of the accelerator consists of two linear transformers with a stored energy of 98 kJ. To reduce the influence of the self-magnetic field on e-beam formation, the vacuum diode is divided into six separate magnetically isolated diodes.

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.

Wide-aperture CO2 lasers pumped with an electron-beam-controlled discharge

This review paper presents the results obtained during the development and study of three high-power wide-aperture CO2 lasers (λ=10.6 μm) pumped with a discharge controlled by an electron beam. In developing these lasers, the method of formation of a space discharge at elevated pressures due to uniform ionization of the working mixture by an electron beam with an energy of some hundreds of kiloelectron-volts was used, which was proposed by researchers at the Instute of High-Current Electronics (IHCE).

Electron-beam-pumped high-power wide-aperture exciplex lasers and laser systems

High-efficiency, high-power pulsedXeCl* andKrF* lasers pumped with an electron beam and laser systems based on these lasers have been developed. This paper describes the principles embodied in their development and design. The results of investigations on the formation of high-quality, high-power pulses are presented. Pulses with a radiation energy of up to 2000 and 100 J have been obtained at λ=308 and 249 nm, respectively, with a minimum 10 μrad divergence of the beam.