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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.

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.

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.

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.

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 ...

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.

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 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.

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 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.

We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, X pinch, plasma focus, vacuum spark, etc. The X generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (20nF, 25nH, 0.2Ω, 100kV). It stores ∼0.8kJ at 80kV charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At 76kV charging voltage the generator provides ∼260kA with 120ns rise time and 5nH inductive load and ∼220kA with 145ns rise time and 10nH. Delay of output pulse relative to high voltage triggering pulse is ∼65ns with 5ns jitter. The dimensions of the generator are 1240×1240×225mm3 and the weight is ∼250kg, and only one high voltage power supply is required a...

An experimental investigation was made of the parameters of lasing as a result of atomic transitions in xenon observed when Ar—Xe and He—Ar—Xe mixtures were excited by an electron beam in a laser chamber with an active volume of ~600 litres. Electron beams from six double acceleration diodes were injected axially symmetric into this chamber. This ensured a more efficient utilisation of the pump energy and a uniform distribution of the laser radiation energy over a transverse exit aperture in the maximum specific input energies. An output radiation energy of the order of 100 J was generated with an efficiency of about 2% at λ =1.73 μm and of the order of 50 J with an efficiency of about 1% at λ = 2.03 μm. An analysis was made of the experimental results and of criteria for the optimisation of the pump parameters in order to improve the output characteristics of a wide-aperture laser operating on the basis of atomic transitions in xenon.