A High-Voltage Pulse Generator with Inductive Energy Storage and Thyratron

A high-voltage pulse generator with an inductive energy storage is described. Its operation is based on the current interruption by a thyratron. It was shown that a T2-500/20 thyratron is capable of reliably interrupting the current with an amplitude of 800–850 A in an inductive energy storage, forming from a low-voltage (0.5–2 kV) power source voltage pulses with an amplitude of up to 90 kV and leading edge duration of 200–250 ns at the load.     

Fast energy output from a high-current pulsed capacitor by using a pseudospark gap

Results of works on a fast energy output from a capacitor by using a pseudospark gap are described. For this purpose, an HCEIcap 50-0.1 capacitor was specially designed with a combined paper-film insulation impregnated with a castor oil with three types of films: mylar, polypropylene, and teflon. A TDI1-50K/50 pseudospark gap was modified so that the total circuit inductance did not exceed 10 nH. During tests at 40–45 kV, current pulses of ～100 kA with a 2.4 × 10¹²-A/s rise rate were obtained.     

A High-Current Pulse Generator SIGNAL with an Inductive Energy Storage and a Microsecond Plasma Opening Switch

The primary energy storage in the SIGNAL installation is a 4.7-F capacitor bank with a stored energy of up to 24 kJ switched by a gas-discharge gap switch of the trigatron type. The plasma source and the design of the microsecond plasma opening switch ensure current flow through this switch and inductive storage for a time of up to 1.7 s. The current amplitude reaches 330 kA. The current switched to the load is 20–300 kA in various modes with a rise time of 10–200 ns. The voltage across the feedthrough insulator reaches 400 kV. The installation is used in experimental studies of linear pinches, capillary discharge, and microsecond plasma opening switches.     

High-voltage high-current air-filled spark gaps of an artificial-lightning-current generator

The designs of two high-voltage high-current air-filled spark gaps of an artificial-lightning-current generator-a two-electrode ДMBP-5 gap for a voltage of up to ±5 kV with graphitized-carbon electrodes and a three-electrode TKBP-50 gap for a voltage of up to ±50 kV with steel electrodes—are described, and their main switching characteristics and the results of tests are presented. Tests were performed with a ДMBP-5 spark gap that switched the normalized long C lightning-current component with an amplitude of up to 0.85 kA, a rise time of up to 0.77 × 10⁵ A/s, a maximum duration of 1000 ms, and a transferred electric charge of up to 210 C. When a TKBP-50 spark gap was used, the normalized pulse A lightning-current component with an amplitude of up to 212 kA, a rise time of up to 7 × 10⁹ A/s, a maximum duration of 500 μs, and an action integral of up to 2.07 × 10⁶ A² s was switched.     

Reversible, high-voltage square-wave pulse generator for triggering spark gaps

A design is presented for a reversible, square-pulse generator that employs coaxial cables for charge storage and pulse formation and a thyratron as the switch. The generator has a nominal output voltage of 5-30 kV and a pulse duration determined by the cable's physical length. Two variations are presented: (1) a single-stage one consisting of cable that is charged via its shield on one end and discharged with a thyratron on the opposite end and (2) a two-stage one having an inverting circuit that uses a coaxial cable to reverse the polarity of the pulse. The generator operates with "flying shields," i.e., high-voltage pulses also propagate on the outside of the cables; this calls for a dedicated insulation that avoids breakdown between sections of the cable's shield. The rise time obtained is mostly dictated by the switching time of the thyratron; with the one we used in the tests, rise times in the range of 30-40 ns were obtained. We present the results obtained in the implementation of the generators as well as its application to fire a large Marx generator.     

Fast high-voltage high-current switch: thyratron-spark gap hybrid

A high-voltage high-current switch using a hydrogen thyratron in series with a two-element spark gap is described. The hybrid switch triggers like a thyratron, turns off like a spark gap, and holds off twice the potential of either element alone.     

Faraday cup with nanosecond response and adjustable impedance for fast electron beam characterization

A movable Faraday cup design with simple structure and adjustable impedance is described in this work. This Faraday cup has external adjustable shunt resistance for self-biased measurement setup and 50 Ω characteristic impedance to match with 50 Ω standard BNC coaxial cable and vacuum feedthroughs for nanosecond-level pulse signal measurements. Adjustable shunt resistance allows self-biased measurements to be quickly acquired to determine the electron energy distribution function. The performance of the Faraday cup is validated by tests of response time and amplitude of output signal. When compared with a reference source, the percent difference of the Faraday cup signal fall time is less than 10% for fall times greater than 10 ns. The percent difference of the Faraday cup signal pulse width is below 6.7% for pulse widths greater than 10 ns. A pseudospark-generated electron beam is used to compare the amplitude of the Faraday cup signal with a calibrated F-70 commercial current transformer. The error of the Faraday cup output amplitude is below 10% for the 4-14 kV tested pseudospark voltages. The main benefit of this Faraday cup is demonstrated by adjusting the external shunt resistance and performing the self-biased method for obtaining the electron energy distribution function. Results from a 4 kV pseudospark discharge indicate a "double-humped" energy distribution.     

A Method for High-Resolution and High-Efficiency Spectroscopy of Ultracold Neutrons at a Small Energy Transfer and Low Scattering Probabilities

Geometry and a method are proposed for spectral measurements of quasi-elastically reflected ultracold neutrons with an energy transfer of up to 200 neV and low scattering probabilities. This method is based on the use of a threshold detector moving in the gravitational field. The attainable energy resolution is 3–5 neV. A Monte Carlo simulation of the spectrometer was performed.     

1/4-J discharge pumped KrF laser

Over 1/4-joule per pulse is obtained from a cable-fed uv preionized discharge device where a faster energy deposition rate compensates for a slower voltage rise time. These slower voltage rise-time devices may be scalable to high repetition rates using conventional thyratron switching techniques.     

Low-pressure gas-discharge current interrupters in a generator of high-voltage nanosecond pulses with an inductive energy storage

Designs of grid units with slotted and multiple-aperture configurations of holes that allow an increase in the stability of the current-cutoff process and a reduction in the time to turn the device off in a high-voltage pulse generator with an inductive energy storage were created. Compared to a TGI2-500/20 thyratron, these designs made it possible to reduce the time instability of the instant of the current interruption by factors of 2 and 5 for switches with the multiple-aperture and slotted configurations of the grids, respectively. These constructions allowed the minimum time for disabling a device to be reduced by 25%.     

A Switching System for Capacitive Energy Storage

The system is intended both for synchronous and programmed discharging of large capacitive energy storage systems. As circuit closers, triggered vacuum switches (TVSs) -43 are used. The TVSs can handle a current of up to 200 kA at a voltage of up to 30 kV and charge of up to 120 C. Each TVS is enclosed in a shielding case with sockets for coaxial cables that connect the switch with the capacitors and the load. Switch-triggering pulses are generated by multichannel high-voltage pulse generators (triggering generators). Each channel is controlled by a programmer via a fiber-optic cable. The programmer operates in conjunction with a computer and provides, in each channel, a prescribed delay of the pulses generated relative to the synchronizing pulse common to the entire system.     

A Gas-Ion Ribbon Beam Source with a Wide-Aperture Cold Hollow Cathode

A source of gas-ion ribbon beams on the basis of a glow discharge in a prolonged electrode system with a closed drift of fast electrons is described. This drift ensures a uniform plasma ion emission in the transverse direction relative to the magnetic induction vector. A discharge with a current of up to 3.5 A and a voltage of 400–600 V in a magnetic field of 6 mT is maintained under a gas flow of 40 cm³atm/min and ensures a saturation ion current density from plasma of up to 4 mA/cm² (±5%) over a length of 50 cm. Using slit-type optics with an aperture of 50 × 1 cm, a ribbon beam with a current of up to 0.2 A and an energy of argon ions of up to 25 keV has been obtained. Methods of the concentration of discharge near the emissive slit and the effect of the electron drift on the ion emission from the plasma are considered. The optimal conditions for ion beam formation are determined.     

The full-voltage effect and the optimal modes of the pulsed conditioning of electrodes in a vacuum

The effect of full voltage on the efficiency of the pulsed conditioning of electrodes in a vacuum is assessed. The efficiency of optimal conditioning modes, estimated from the quality of the cathode surface relative to gaps of centimeter length and long-acting voltage, increases by more than two orders of magnitude when the pulse duration and interelectrode gap are reduced. An increase of up to one order of magnitude is achieved by reducing the gap width to micron sizes during conditioning. The efficiency increases by a factor of as much as 30 by reducing the pulse duration and raising the optimal regimes pulse power.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 92–94.Original Russian Text Copyright © 2005 by Emelyanov, Emelyanova, Kubyshkina.     

Selection of the Shaping Circuits of a Multilayer Semiconductor Spectrometer of Charged Particles

The influence of the charge collection time in silicon detectors on the accuracy of charged particle energy measurements is considered. Calculation and experimental data show that this parameter exerts a significant effect on the selection of the shaping time constants of multilayer silicon spectrometers. This is especially important for systems based on Si(Li) detectors, which are designed for detecting long-range charged particles (p, d, t) with energies E 100 MeV. It is shown that the time constant = 1.5 s ensures a high accuracy in the absolute energy calibration.     

An Optical-Fiber Setup for Inert Particle Concentration Measurements

An optical-fiber setup employing laser light designed to measure concentrations of 50-to 500-m particles moving with a speed of up to 10 m/s is described. The time resolution, the measurement time, and the counting of pulses reflected from the particles are programmed. The setup has the following basic parameters: time resolution is 10 s, spatial resolution is 50 m, sample size is up to 32 × 10³, and particle counting error is within 1%. The setup was applied to measurement of the solid-phase concentration in a two-phase flow in a volum concentration range of up to 30%.     

Laser‐induced reversion of precipitates in an Al‐Li alloy: Study on temperature rise in pulsed laser atom probe

The influence of tuning the laser pulse energy during the analyses on the resulting microstructure in a specimen utilizing an ultra‐fast laser assisted atom probe was demonstrated by a case study of a binary Al‐Li alloy. The decomposition parameters, such as the size, number density, volume fraction, and composition of precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser pulse energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al‐Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser pulse energy of 100 pJ was in fairly good agreement with reported range of solvus temperature, suggesting a result of reversion upon heating due to laser pulsing. Microsc. Res. Tech. 79:727–737, 2016. © 2016 Wiley Periodicals, Inc.     

AУPT-1M accelerator for radiation technologies

AУPT-1M modernized electron accelerator with an accelerating voltage up to 1 MV, a 1-kW electron beam power, and a 100-ns pulse duration is described. As compared to the prototype (УPT-1 accelerator), the layout of assemblies is changed in it, allowing one to place it in rooms with heights up to 2.5 m. It uses Murata capacitors and a ТQPи1–10k/75 thyratron with a cold cathode for switching. The computer-aided parameter-monitoring system is created. A metal-ceramic cathode consisting of several elements with ～15% nonuniform current density distribution of the electron beam on the exit foil was used to obtain an electron beam with a width of up to 400 mm. The accelerator can be used in radiation technologies in layers with a thickness of up to 0.3 g/cm².     

A method for measuring spectral and time characteristics of mixed pulsed gamma-neutron fields with scintillation and Cherenkov detectors with nanosecond time resolution

A method for measuring spectral and time characteristics of pulsed mixed (n, γ) fields is described. The essence of this method is that a sequence of signals from individual (n, γ) particles registered by (n, γ) detectors is written in a computer with the subsequent amplitude-time analysis of the signal parameters. Fast scintillation and Cherenkov detectors with FWHM of pulses of ～1.5 and 2.5 ns, respectively, are used as (n, γ) detectors. A TDS-3054 broadband digital oscilloscope records signals and transmits them to the computer through a GPIB-USB interface. The equipment used ensures efficient detection of (n, γ) particles at detector counting rates of up to ～2 × 10⁸ pulses/s. The efficiency of this method has been tested in measurements of characteristics of (n, γ) radiation fields from an ИНГ-031 pulsed neutron generator and from a copper target irradiated with a beam of carbon nuclei with an energy of 200 MeV/amu from the TVN-ITEF acceleration-storage complex.     

The RFR-4 X-ray Streak Camera

The RFR-4 X-ray streak camera with a slit scan designed on the basis of an X-ray sensitive evacuated image tube is described. The obtained images are recorded using a charge-coupled device (CCD) camera. The basic parameters of the X-ray streak camera are as follows: (1) the recorded spectral range starts at 0.1 keV; (2) the time resolution is as high as 30 ps; (3) the spatial resolution is five pairs of lines per millimeter (for a contrast ratio of 0.5); (4) the dynamic recording range is as high as 2000; and (5) the detectability is 2 × 10⁵ quanta/(cm²ns) (for a quantum energy of 1.5 keV). The design of the device and the purpose and operation of its components are described. The streak camera is equipped with a gate-valve unit with an autonomous evacuation system; this allows one to use it in installations where the working-chamber pressure increases dynamically up to 0.1 Torr. The sharp-focusing operating mode, which allows one to increase the device's sensitivity by an order of magnitude without loss in the time resolution, is described. The streak camera was used to record the X radiation in experiments with various targets performed at the ISKRA-4 and ISKRA-5 laser installations and the SIGNAL-2 Z-pinch installation.