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The objectives of this tutorial are as follows: 1) to help students and researchers develop a basic understanding of how pulsed-power systems are used to create high-energy-density (HED) matter; 2) to develop a basic understanding of a new, compact, and efficient pulsed-power technology called linear transformer drivers (LTDs); 3) to understand why LTDs are an attractive technology for driving HED physics (HEDP) experiments; 4) to contrast LTDs with the more traditional Marx-generator/pulse-forming-line approach to driving HEDP experiments; and 5) to briefly review the history of LTD technology as well as some of the LTD-driven HEDP research presently underway at universities and research laboratories across the globe. This invited tutorial is part of the Mini-Course on Charged Particle Beams and High-Powered Pulsed Sources, held in conjunction with the 44th International Conference on Plasma Science in May of 2017.

The technique of a linear transformer driver (LTD) now allows building the generators of high-power nanosecond pulses with the current rise time of $\sim 100$ ns without intermediate power compression stages. This technique is being examined for use in high-current high-voltage electron sources based on plasma-filled diodes. The power of a plasma-filled diode is determined by the driving circuit parameters and the transition diode resistance. The problem of power rise can be solved by increasing the stored energy in the circuit inductance provided that the diode resistance rise rate is constant. In experiments on the LTD (53 nF, 480 kV), the possibility has been checked out for such increase in the stored energy. A current increase from 50 to 180 kA was obtained by increasing the current rise rate from 0.4 to 1.9 kA/ns. Stored energy has been increased, respectively, from 0.2 to 3.6 kJ. The time of energy transfer into the circuit inductance was about 120–140 ns. Maintaining the diode resistance rise rate at 0.5 $\Omega $ /ns has been shown. Diode power has been increased up to 170 GW. Further increase in power of the plasma-filled diode has been obtained using simulation circuit of the Megavolt (MV) range LTD. To simulate such a linear transformer, the driver circuit was made as Marx generator with coaxial water line (5.3 $\Omega $ , 56 ns, and 1.5 MV), providing a current input of 160 kA into the 550-nH inductance in 120 ns. Stored energy in the inductance was about 7 kJ. The following diode parameters were obtained: 150 kA, 1.9 MV, and 250 GW at a resistance rise rate more than 0.5 $\Omega $ /ns. The experiments prove that the resistance rise rate of the plasma-filled diode is constant on increasing the stored energy in the inductance up to 7 kJ. It allows scaling the power of an electron source based on the plasma-filled diode.

A test bench for studying two-electrode spark gaps rated at a voltage of 300 kV and a pulse repetition rate of up to 10 Hz and operating in air at elevated pressure. The typical time of pulse charging of a capacitive storage in the bench equals about 100 μs. The object of investigation is a spark gap the operating stability of which at a level of 10% of the rate voltage is achieved by initiating a corona discharge at the prebreakdown stage. It is shown that unstable operation is due to the accumulation of nitrogen oxides in the gap. To maintain the oxide content at an acceptable level, continuous gas purging is applied and necessary gas flow rates are estimated.

An ultra-wideband radiation source based on the excitation of a 64-element array of combined antennas by a generator of bipolar voltage pulses with the length of 1 ns, amplitude of 200 kV and pulse repetition rate of 100 Hz has been designed and studied. The peak power of the voltage pulse was 3.2 GW. The effective potential of the ultra-wideband source radiation reached 4.3 MV.

This paper reports on the creation of a THL-100 multi-terawatt hybrid laser system based on a Start-480M titanium-sapphire starting complex and photochemical XeF(C-A) amplifier with a 25-cm aperture. The complex produces 50-fsradiation pulses of energy up to 5 mJ at a second harmonic wavelength of 475 nm. The active medium of the amplifieris created in a XeF 2 /N 2 mixture under vacuum-ultraviolet radiation of electron beam-excited xenon. The results of firstexperiments on femtosecond pulse amplification in the active medium of the XeF(C-A) amplifier are presented todemonstrate that a laser beam peak power of 14 TW has been attained.Keywords: Chirped pulses; Femtosecond pulses; Hybrid (solid/gas) laser system; Photochemical XeF(C-A) amplifier;Second harmonic INTRODUCTIONAt present, the development of ultra-high power laser sys-tems with a pulse duration of 10–100 fs is based mainly onnear-infrared solid-state titanium-sapphire or parametric am-plifiers and amplification of positively chirped pluses, i.e.,stretched in time (0.5–1 ns), by linear frequency modulation(Strickland & Mourou, 1985) with their subsequent com-pression to the initial duration. Stretching of a pulse is re-quired to decrease its power below a threshold at which thebeam is self-focused; in solid-state systems, pulses are nor-mally stretched about 10

The design and results of investigation of a two-electrode spark-gap switch aimed at connecting a capacitive energy storage are presented. Experiments are carried out at the following parameters: the operating voltage 300 kV; the switching energy, 450 J; the spark-gap switch current, 20 kA; and the pulse repetition rate, 10 Hz. Owing to specific self-breakdown conditions under which a spark current is preceded by a prebreakdown corona, the voltage stability of the switch within 10% is reached.

Data are reported for the performance of subnanosecond high-pressure gas-discharge switches aimed at generating high-voltage bipolar voltage pulses with a width of less than 1 ns, an amplitude of up to 200 kV, and a repetition rate of 100 Hz. Pulse formers, in which the polarity of the current passing through the switch does not change in the course of switching, seem to be the most appropriate. When the current changes sign, passing through zero, the effect of its momentary interruption is observed. The explanation of this effect is that, when the voltage across the gap reverses, a certain time interval is necessary for a cathode layer to form, which can transmit a high discharge current at a low voltage drop across the layer.

Sources of high-power ultra-wideband electromagnetic pulses of nanosecond duration are described. A bipolar voltage pulse with a length of 0.5 ns and an amplitude of ∼200 kV is fed to the input of a radiating system (a 16-element array antenna or a single antenna). The values of the effective radiation potential EpR = 260 kV for a source with a single antenna and EpR = 690 kV for a source with a 16-element antenna array were obtained at a pulse repetition frequency of 100 Hz.

High-energy switches and trigger generators are required for MJ-level capacitor banks. We have developed a compact gas switch and a matched series injection trigger generator. A series inductance is required for isolation of the trigger pulse from the surrounded circuit. A saturable inductor is employed here because low inductance is needed after the switch breakdown. The switch is of coaxial two-electrode design with electrodynamic acceleration of a spark channel. The switch operates at atmospheric pressure. The spark gap can be triggered reliably down to zero voltage (at 50 kV self-breakdown voltage) with less than 35 ns timing jitter. Energy losses in this spark gap have been accurately investigated. The main results are as follows: energy losses in the switch do not exceed 4% at voltages higher than 15 kV, i.e., when operation voltage exceeds ∼36% of the self-breakdown voltage. The spark gap is designed for 24 kV charging voltage, at a current up to 250 kA, and ∼70 C charge transfer. In this paper, we present a design for the spark gap, inductor and trigger generator. Test bed schematics and results of the tests are also described.

Power increase of high current relativistic electron beam is related to the necessary increase in the current density. Plasma-filled diode concept looks promising from that point view. Electron beam generation occurs in a plasma-filled diode in a double sheath with plasma as an anode boundary. It provides smaller accelerated gap, lower impedance and larger current density than it possible with a vacuum diode for a given voltage. It also provides possibility to exclude the anode foils, separating regions of the beam generation and transportation to target.

This paper describes the configuration and operation of a seven-cavity linear transformer driver (LTD) system. This LTD system is configured to deliver ~1 MV and 125 kA into a critically damped load. A detailed transmission line model coupled to particle-in-cell simulations is used to assess the system electrical performance. The evolution of the electron power flow in negative polarity is simulated, and the impact of this flow on the operation of the system with a large-area hollow electron beam diode is examined. The simulation results are compared with available electrical measurements and with dose rate measurements where a flash X-ray pulse is produced by an annular electron beam diode. These comparisons suggest that the LTD system meets the design specifications and is a robust pulsed power architecture. Additionally, the positive polarity operation for the LTD system driving a rod-pinch diode load is modeled to further assess the utility of the LTD system

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.

We have developed a compact gas switch intended for operation in oscillatory (low damping) regime of discharge. It is two-electrode switch with electrodynamic acceleration of a spark channel and a matched series injection trigger generator. A series inductance is employed for isolation of a trigger pulse from a surrounded circuit. Two operations regimes have been investigated, namely "fast" regime with current amplitude ~ 160 kA, total charge ~ 12 C, period of oscillations 60 μ s, full pulse length ~ 400 μ s and "slow" regime with current amplitude ~ 30 kA, total charge 18 C, period of oscillations 360 μ s, full pulse length ~ 3 ms. The spark gap can be triggered reliably from 16 to 50 kV (at 72 kV self-breakdown voltage). Time delay in firing was less than 35 ns at 1 ns jitter at 30 mm gap and 40 kV charging voltage. The spark gap is designed for 50 kV charging voltage, at a current up to 200 kA, and up to 20 C charge transfer. Arc motion and electrodes erosion in this spark gap have been investigated. The main results are as follows: the arc channel moves on ~ 18 cm in fast regime and ~ 25 cm in slow regime. Results of the switch operation in slow and fast regimes with operational voltage of 40 kV and stored energy 32 kJ promise to get high lifetime. In this paper we present design for the spark gap and trigger generator. Test bed schematics and results of the tests are also described.

Preliminary creation of ion flow in a vacuum diode before applying the voltage pulse allows removing the beam current limitation by own space charge, reducing the diode impedance, and increasing the beam power. The sources based on the surface dielectric breakdown are most widely used to create a plasma flow. Plasma extends as a result of hydrodynamic expansion with a velocity of ∼106 cm/s determined by the plasma temperature (units of eV). Besides this, the ions with the velocities exceeding the thermal velocity are recorded. It is evident that this flow can be used for ion compensation of the electron beam charge in high-current relativistic diodes. This paper presents the results of oscillographic study of the ion flow propagation from a capillary plasma gun in combination with single-frame photography of plasma glow with a resolution up to 3 ns. Ignition of a high-current low-resistance discharge with the current of 100 kA in the absence of complete filling of the diode gap with plasma is demonstrated. The situation in which plasma fills only a part of the diode gap prior to ignition of high-current discharge is favorable for the realization of the current cutoff with a high rate.

The characteristics of the plasma-filled diode when changing the current rise rate by 2 times were obtained. The rise rate was varied by changing the inductance of the secondary coil vacuum line of the linear transformer used as a pulsed power driver. The possibility of increasing the current amplitude by increasing its rise rate was demonstrated at fixed initial conditions. So, increase in the current rise rate by 2 times resulted in the rise of the current amplitude from 100 to 185 kA, transmitted charge from 6 to 10 mC while retaining the low-resistance phase duration of 100 ns. At the current amplitude rise by more than 1.5 times, the diode impedance rise rate in a high-resistance phase was retained at the level of 0.5 Ω/ns which allowed increasing the diode power by 1.6 times from 100 to 160 GW. The diode voltage remained at the level of approximately 1 MV due to the fast current drop in a high-resistance phase. Conservation of the resistance rise rate allows forecasting the growth of the diode voltage proportional to the current in case of increasing the current rise rate without reducing the inductance.

Long time implosion experiments with argon double gas puffs have been conducted on the GIT-12 [S. P. Bugaev et al., Izv. Vyssh. Uchebn. Zaved., Fiz. 40, 38 (1997)] generator at the current level of 2.2–2.4 MA. A double gas puff was used as one of the alternative ways to improve implosion stability at implosion times from 230 to 340 ns. The results of these experiments were compared with two-dimensional snowplow simulations. The experiments and the simulations show that the final pinch is sufficiently stable when the inner-to-outer shell mass ratio is greater than 1. The maximum argon K-shell yield obtained in the experiments is 740 J/cm with 220 GW/cm radiation power. At the long implosion times, the K-shell yield obtained in the double gas puff implosion is twice the K-shell yield of a 4-cm-radius single gas puff, with more than an order of magnitude increase in radiation power.

Experimental and theoretical investigations were made of the excitation and emission from a high-power HF laser pumped by a nonchain chemical reaction initiated by a radially converging electron beam. The distribution of the specific radiation energy in the output beam was determined and the distribution of the input energy over the laser chamber cross section was calculated for various gas mixtures. The space-charge field influenced the input energy distribution. The output radiation energy of a mixture of the SF6 : H2=8 : 1 composition was ~115 J at a pressure of 0.45bar when the active volume was ~30 litres, the efficiency relative to the input energy was ~7%—8%, and the distribution of the radiation energy over the output beam cross section was relatively uniform. For the same input energy, because of the high density of SF6, a pressure jump in SF6— H2(D2) mixtures resulting from the combined effect of the electron beam injection and the chemical reaction was several times less than in active mixtures of exciplex lasers.

A novel configuration of a deuterium $z$ pinch has been used to generate fusion neutrons. Injecting an outer hollow cylindrical plasma shell around an inner deuterium gas puff, neutron yields from DD reactions reached ${Y}_{\mathit{n}}=(2.9\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}1{0}^{12}$ at 700 ns implosion time and 2.7 MA current. Such a neutron yield means a tenfold increase in comparison with previous deuterium gas puff experiments at the same current generator. The increase of beam-target yields was obtained by a larger amount of current assembled on the $z$-pinch axis, and subsequently by higher induced voltage and higher energies of deuterons. A stack of CR-39 track detectors on the $z$-pinch axis showed hydrogen ions up to 38 MeV. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial time-of-flight detectors, respectively. The number of DD neutrons per one joule of stored plasma energy approached $5\ifmmode\times\else\texttimes\fi{}{10}^{7}$. This implies that deuterium gas puff $z$ pinches belong to the most efficient plasma-based sources of DD neutrons.

In this paper we present the design and test results of pulse generators based on air-insulated linear-transformer-driver stages that drive a vacuum transmission line. A custom designed unit, referred to as a capacitor block, was developed for use as a main structural element of the transformer stages. It incorporates two capacitors GA 35426 (40 nF, 100 kV) and a multichannel multigap gas switch. Two types of stages were developed: (1) stage LTD-20 with four modules in parallel and five capacitor blocks in each module (in tests of this stage current amplitude up to 850 kA with $\ensuremath{\sim}140\text{ }\text{ }\mathrm{ns}$ rise time was obtained on a $0.05\text{ }\ensuremath{\Omega}$ load at 100 kV charging voltage); (2) stage LTD-4 with two modules in parallel and two capacitor blocks in each module. Several installations were built on the base of these stages, including a linear transformer, consisting of two identical LTD-20 stages in series, and a high power electron accelerator on the base of LTD-4 stages. The design, tests results, and main problems are presented and discussed in this paper for these installations.

A novel configuration of a deuterium z-pinch has been used to generate a nanosecond pulse of fast ions and neutrons. At a 3 MA current, the peak neutron yield of (3.6 ± 0.5) × 1012 was emitted within 20 ns implying the production rate of 1020 neutrons/s. High neutron yields resulted from the magnetization of MeV deuterons inside plasmas. Whereas deuterons were trapped in the radial direction, a lot of fast ions escaped the z-pinch along the z-axis. A large number of >25 MeV ions were emitted into a 250 mrad cone. The cut-off energy of broad energy spectra of hydrogen ions approached 40 MeV. The total number of >1 MeV and >25 MeV deuterons were 1016 and 1013, respectively. Utilizing these ions offers a real possibility of various applications, including the increase of neutron yields or the production of short-lived isotopes in samples placed in ion paths. On the basis of our experiments with various samples, we concluded that a single shot would have been sufficient to obtain GBq positron activity of 13N ...

Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6 ohms damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (approximately 0.08 ohms). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70-100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70-100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24x1.2x0.18 m(3) and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus.

In this article we present the design and test results of the most powerful, fast linear transformer driver (LTD) stage developed to date. This 1-MA LTD stage consists of 40 parallel RLC (resistor R, inductor L, and capacitor C) circuits called ``bricks'' that are triggered simultaneously; it is able to deliver $\ensuremath{\sim}1\text{ }\text{ }\mathrm{MA}$ current pulse with a rise time of $\ensuremath{\sim}100\text{ }\text{ }\mathrm{ns}$ into the $\ensuremath{\sim}0.1\mathrm{\text{\ensuremath{-}}}\mathrm{Ohm}$ matched load. The electrical behavior of the stage can be predicted by using a simple RLC circuit, thus simplifying the designing of various LTD-based accelerators. Five 1-MA LTD stages assembled in series into a module have been successfully tested with both resistive and vacuum electron-beam diode loads.

Sharing similarities with the GEPI pulser which is dedicated to Isentropic Compression Experiments (ICE), VELOCE, an even more compact electrical pulser, has been designed and built in duplicate for SNL and WSU. This type of machine complements gun and laser facilities in the study of material response. In order to achieve a broad loading capability and fast turn around, the design is built around a solid dielectric transmission line to couple current from low inductance capacitors and electrically triggered switches. Peaking capacitors enhanced by a low inductance, multi‐channel sharpening switch reduce the quarter period of the pulser to about 470 ns (0–100%). Gas mixtures in the switch cavity and inductances in parallel allow modification of the shape of the induced pressure wave. At 80 kV of charge voltage, the peak current can reach 3.5 MA. Design of the pulser, range of pressures and velocities, as well as potential applications are presented. A consistent numerical tool developed for pulsers design based on a circuit code coupled to a 1D MHD code is also introduced.

The multi-stage hybrid laser system producing ultrashort pulses of radiation with peak power ~10 14 - 10 15 W now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amplification of ultrashort pulses produced by solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C-A)laser excited by VUV radiation of an e-beam pumped Xe 2 lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(CA) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High- Current Electronics: electron energy ~600 keV, specific input power ~ 300-500 kW/cm 3 , e-beam pulse duration ~ 100- 200 ns. A possibility of using Kr 2 F as an active medium with saturation energy 0.2 J/cm 2 for amplification of ultrashort laser pulses is also under consideration. There was theoretically demonstrated that the energy of a laser pulse at the exit of the final stage of the laser system could come up to ~ 17 J with pulse duration ~50 fs in the case of KrF laser, and ~75 J with pulse duration of 25 fs in the case of XeF laser. Two Ti:Sa laser systems producing ~50 fs pulses with energy ~0.5 mJ at the wavelength 248 nm and ~5 mJ at the wavelength 480 nm have been already developed and are being now installed at the Lebedev Institute. Preliminary experiments on amplification of UV femtosecond pulses were carried out with electric discharge KrF laser amplifier.

Summary form only given. Within the context of the pulsed power system's development undertaken by CEA for the megajoule laser (LMJ) facility, new capacitor bank module (CBM) is developed by ILICE (Tomsk) and ITHPP (France). Two CBMs were produced and tested in Tomsk. Large number of modules (480) in the complete LMJ installation imposes strict requirements to CBM's parameters. These include reliability of the elements (30 years estimated LMJ lifetime), cost minimization, ability' to withstand failure regime, stability from shot to shot in controlled parameters, limits on size and weight, easy maintenance, and a row of other technical requirements. Main parts of the CBM are: HV power supply, control system, air conditioning system, capacitor block, cables delivering the energy to the load. The capacitor block includes 1 preionization and 10 main capacitors, 1 preionization and 1 main switches, charging and damping resistors, pulse shaping inductors, high voltage relays and safety system. Control system provides operation of the capacitor block in selected mode, monitoring and recording currents as well as voltages, command for dumping at failure and some other functions. CBM's parameters are: total capacitance 3000 muF, charge voltage up to 24 kV, peak current amplitude 240 kA, peak stored energy 864 kJ, pulse width at 10% of peak power 360 mus, dimensions 2.3times1.5times2.5 m3, weight ~2500 kg. In nominal regime (24 kV, 40 m cables), the energy delivered to the flash lamps in each channel is 74 kJ (86% efficiency). No failures were observed in more than 1000 test shots and all the CBM parameters are well within the requirements. Detailed description of the CBM and test results is given in the report.

The multi-stage hybrid laser system producing ultrashort pulses of radiation with peak power ~10 14 - 10 15 W now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amplification of ultrashort pulses produced by solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C-A)laser excited by VUV radiation of an e-beam pumped Xe 2 lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(CA) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High- Current Electronics: electron energy ~600 keV, specific input power ~ 300-500 kW/cm 3 , e-beam pulse duration ~ 100- 200 ns. A possibility of using Kr 2 F as an active medium with saturation energy 0.2 J/cm 2 for amplification of ultrashort laser pulses is also under consideration. There was theoretically demonstrated that the energy of a laser pulse at the exit of the final stage of the laser system could come up to ~ 17 J with pulse duration ~50 fs in the case of KrF laser, and ~75 J with pulse duration of 25 fs in the case of XeF laser. Two Ti:Sa laser systems producing ~50 fs pulses with energy ~0.5 mJ at the wavelength 248 nm and ~5 mJ at the wavelength 480 nm have been already developed and are being now installed at the Lebedev Institute. Preliminary experiments on amplification of UV femtosecond pulses were carried out with electric discharge KrF laser amplifier.

The multi-stage hybrid laser system producing ultras hort pulses of radiation with peak power ~10 14 - 10 15 W being now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amp lification of ultrashort pulses produced by a solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C- : )-laser excited by VUV radiation of an e-beam pumped Xe 2 lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(C-A) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High-Current Electronics: electron ener gy ~600 keV, specific i nput power ~ 300-500 kW/cm

Results of the experiments carried out on the GIT‐12 generator at the current level of 3.5 MA and the Z‐pinch implosion times from 700 ns to 1.1 μs are presented. A multi‐shell (triple‐shell) load configuration with the outer gas puffs (neon) and the inner wire array (aluminum) was used in the experiments. In the course of the research, implosion dynamics of the triple‐shell z‐pinch was studied, and the radiation yield in the spectral range of neon and aluminum K‐lines have been measured. Optimization of the inner wire array parameters aimed at obtaining the maximum aluminum K‐shell radiation yield has been carried out. As a result of optimization of the gas‐puff‐on‐wire‐array Z‐pinch load, the aluminum K‐shell radiation yield (hv> 1.55 keV) up to 4 kJ/cm in the radiation pulse with FWHM less than 30 ns has been obtained. Comparison of the experimental results with the results of preliminary 1D RMHD simulations allows a conclusion that at least 2/3 of the generator current is switched from a gas puff to a...

The Project of petawatt excimer laser was started at Lebedev Physical Institute (LPI) in collaboration with High‐Current Electronics Institute (HCEI). It utilizes Ti:Sa front‐end to generate 1mJ, 50 fs pulses, frequency conversion into 2ω or 3ω and direct amplification of short pulses in a chain of excimer amplifiers with e‐beam or photochemical pumping. Multi‐terawatt output in 20‐J, subpicosecond pulses at KrF (λ = 248 nm) is projected being combined with 4‐kJ, nanosecond pulses. Petawatt femtosecond pulses at Kr2F (400 nm) might be expected, if transient absorption could be reduced in e‐beam‐pumped gain medium. For photochemically‐pumped XeF amplifiers (480 nm) multi‐petawatt level is attainable with a high temporal contrast.

The development of a high-power HF laser pumped by a chemical nonchain reaction initiated by a radially converging electron beam is reported. A radiation energy of ∼ 115 J with an efficiency of ∼ 8% in terms of deposited energy has been achieved in a mixture with an active volume of ∼ 30 liters. It is shown that because of the high SF6 density, the total pressure jump in SF6–H2(D2) mixtures caused by the electron beam injection and the chemical reactions is several times smaller than that in the active mixtures of exciplex lasers for the same input energies. This factor considerably facilitates the development of wide-aperture HF and DF lasers with an SF6 fluorine donor pumped by an electron-beam-initiated chemical nonchain reaction.

A 250 J/210 ns four-stage XeCl laser system named Photons has been developed. Five lasers in MOPA chains characterized by different pumping techniques are described. Also, the main experimental results of the Photons are given.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Particle-in-cell simulations of a seven-cavity linear transformer device system are carried out to assess, in part, the evolution of the electron power flow in negative polarity and the impact of this flow on the operation of the system with simple large-area hollow electron beam diode loads.

This paper describes a multiterawatt hybrid laser system based on a Ti : sapphire front end and 25-cm-aperture photodisso- ciation XeF(C - A) amplifier. The front end generates 50-fs pulses with second-harmonic (l = 475 nm) energies of up to 5 mJ. The gain medium of the amplifier is produced in a XeF2 - N2 mixture by VUV radiation excited in xenon by a high-power electron beam. Through amplification of a negatively chirped 1-ps pulse, followed by pulse compression in bulk fused silica, a peak power of 14 TW, record-high for the visible range, has been achieved.

Summary form only given, as follows. All wire array implosion experiments have been carried out on the inductive storage generators GIT-4 (0.6MJ, 1.5 MA) and GIT-8 (1.2 MJ, 1.9 MA). The maximum radiation power in the region of 1.5-2 keV observed in the experiments were 70 GW/cm and 150 GW/cm respectively for the GIT-4 and GIT-8 generators. The increase in the radiation power is primarily related to the increase in the current derivative (5.10/sup 13/ A/s for the GIT-8, and 2.10/sup 13/ a/s for the GIT-4). The measurements of the K-shell radiation power and the K-shell radiation yield as a function of liner mass and diameter have been performed. The results of the recent gas-puff on wire array experiments are also presented.

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.

A high current e-beam accelerator for pumping of the 200 liter eximer laser is developed providing electron energy of 550 keV, diode current of 320 kA, e-beam current of 250 kA. The high voltage part of the accelerator consists of two linear transformers with the stored energy of 98 kJ. In order to reduce the influence of the self magnetic field on e-beam formation the vacuum diode is divided into 6 separate magnetically isolated diodes.

The results are presented of experimental and theoretical investigations of excitation and generation of the HF laser pumped by nonchain chemical reaction initiated by a beam of electrons as well as of the KrF and XeCl lasers pumped by beams of electrons. The effect of the volume charge field on the distribution of energy over the cross section of a laser cell and of the radiant energy density over the cross section of an output laser beam in mixtures with different concentrations of halogen is analyzed. The output energy density distribution over the beam cross section for lasers excited by the radially convergent beam of electrons and the total pump energy are determined. The pump energy distribution over the laser cell cross section and the total pump energy in various gas mixtures are calculated.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Basing on energetic processes studying in the near-field radiator zone, a new concept of antenna synthesizing for ultrawideband electromagnetic pulse radiation has been suggested. The results of experimental investigations of the antennae developed with using of this concept for high-power applications are presented. The antennae have small dimensions, high electrical strength, cardioid pattern with linear polarization of the pulse radiated and they are ideally adapted to be used as a steering antenna array element. A high-voltage nanosecond bipolar pulse generator design to excite antennae is described.

A high-voltage pulse technology is one of effective techniques for the disintegration and milling of rocks, separation of ores and synthesized materials, recycling of building and elastoplastic materials. We present here the design and test results of two portable HV pulsed generators, designed for materials fragmentation, though some other technological applications are possible as well. Generator #1 consists of low voltage block, high voltage transformer, high voltage capacitive storage block, two electrode gas switch, fragmentation chamber and control system block. Technical characteristics of the #1 generator: stored energy in HV capacitors can be varied from 50 to 1000 J, output voltage up to 300 kV, voltage rise time ~ 50 ns, typical operation regime 1000 pulses bursts with a repetitive rate up to 10 Hz.Generator #2 is made on an eight stages Marx scheme with two capacitors (100 kV–400 nF) per stage, connected in parallel. Two electrode spark gap switches, operated in atmospheric air, are used in the Marx generator. Parameters of the generator: stored energy in capacitors 2÷8 kJ, amplitude of the output voltage 200÷400 kV, voltage rise time on a load 50÷100 ns, repetitive rate up to 0.5 Hz. The fragmentation process can be controlled within a wide range of parameters for both generators.

Experiments with deuterium (D2) triple shell gas puffs were carried out on the GIT-12 generator at a 3 MA current level and microsecond implosion times. The outer, middle and inner nozzle diameters were 160 mm, 80 mm and 30 mm, respectively. The influence of the mass of deuterium shells on neutron emission times, neutron yields and neutron energy spectra was studied. The injected linear mass of deuterium varied between 50 and 255 µg cm−1. Gas puffs imploded onto the axis before the peak of generator current at 700–1100 ns. Most of the neutrons were emitted during the second neutron pulse after the development of instabilities. Despite higher currents, heavier gas puffs produced lower neutron yields. Optimal mass and a short time delay between the valve opening and the generator triggering were more important than the better coincidence of stagnation with peak current. The peak neutron yield from D(d, n)3He reactions reached 3 × 1011 at 2.8 MA current, 90 µg cm−1 injected linear mass and 37 mm anode–cathode gap. In the case of lower mass shots, a large number of 10 MeV neutrons were produced either by secondary DT reactions or by DD reactions of deuterons with energies above 7 MeV. The average neutron yield ratio Y>10 MeV/Y2.5 MeV reached (6 ± 3) × 10−4. Such a result can be explained by a power law distribution for deuterons as . The optimization of a D2 gas puff Z-pinch and similarities to a plasma focus and its drive parameter are described.

A series of collaborative experiments on complex plasma loads have been carried out on the large inductive energy storage (IES) generator, GIT-4, over the last three years. The aim of the experiments is to explore the different configurations for the formation of ultra-high energy density plasmas in high voltage pulsed power systems by direct electromagnetic energy coupling. In this paper, the authors present some of the underlying philosophy on these experiments and the results obtained. Particular emphasis is placed on the pulsed power aspects and the effect of source-load coupling.

The results of an experimental study of the laser action on XeCl*, KrF*, and N2 molecules and by the atomic transitions of xenon and neon are presented. Laser radiation energies of 110, 90, 3, 100, 50, and 0.5 J have been obtained at (lambda) equals 308, 249, 358, 1730, 2030, and 585 nm, respectively. The experiments were carried out on two accelerators producing radially convergent electron beams, that pumped laser chambers 20 mm in diameter with a beam current of FWHM duration 0.3, 30, and 100 microsecond(s) .© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.