Том 60, № 1 (2017)

A high-voltage switch on the basis of a small unit of series-connected high-voltage integrated pulse thyristors (HVIPTs), which were developed at the Ioffe Physical Technical Institute, was designed and investigated. At a power voltage of 25 kV, current pulses of microsecond duration with an amplitude of 2.8 kA and a rise time of 0.8 μs were switched. The attained current density through an HVIPT (5.6 kA/cm²) appreciably exceeds the permissible current density for conventional thyristors. It is shown that the developed HVIPT unit can be used in the triggering circuit of a high-power assembly of reverse switch-on dynistors (RSDs) at an operating voltage of 25 kV, which consists of 14 series-connected dynistors with a diameter of their structures of 24 mm. The RSD switch with a triggering circuit on the basis of HVIPTs allowed switching of rapidly rising current pulses with an amplitude of 20 kA and a duration of 150 μs. The small dimensions of the HVIPT unit (4 × 10 × 32 cm) and the RSD assembly (7 × 7 × 34 cm) determine the wide prospects for using them in high-power pulse technology.

A prototype of a compact sectioned high-voltage source for the modernization of a tandem accelerator with vacuum insulation has been created at the Budker Institute of Nuclear Physics. In contrast to the existing voltage source, it is possible to specify the potential at the accelerating electrodes directly from the rectifier sections, as well as to decrease the accelerator height. This paper presents a new source design and the test results.

A device on the basis of a double directional bridge for separating ultrawideband pulse signals that are incident on and reflected from an arbitrary load is described. The experimental results from studies of the device using picosecond (40 ps) and nanosecond (10 ns) electrical pulses are presented. A test pulse that feeds the input port comes to a device under test (DUT) with an attenuation of 5 dB. The device separates the resulting incident and reflected pulses that arrive at different ports. The isolation between the ports of the incident and reflected pulses is at least 20 dB in the operating-frequency range from 300 kHz to 16 GHz.

The results of the development of a universal experimental device and the general methodology for modeling wave electromagnetic processes in multiply connected quasi-optical resonance systems, which contain periodic inhomogeneities of various modifications, at which surface waves of a dielectric waveguide are transformed into bulk electromagnetic wave, are presented. The optimal modeling modes and the key parameters of the investigated electrodynamic systems are selected. The block diagram of the experimental device, which is implemented in the wavelength range λ = 4–8 mm, is described. A general methodology for modeling the wave electromagnetic phenomena in resonance and wave-guiding multiply connected quasioptical systems is outlined for the first time by the authors.

A method for studying the internal structure of a sample by detecting scattered synchrotron radiation using a pinhole camera is considered. The beam for imaging is shaped like a plane that intersects the sample. The characteristic spatial resolution of the method is 100 μm. Examples of the obtaining of images are presented, and the differences of this method from traditional techniques are discussed.

Injection of high-power flows of high-energy neutral atoms is often required in modern facilities designed for fusion research. At energies of several hundreds keV, obtaining neutral atom flows is ineffective and converting them from negative ion beams is expedient. The efficiency of negative-ion production increases by many times if a cesium film is applied to the surface on which negative ions are produced. An optimized system of distributed cesium feeding is described. Using this system, it is possible to transport cesium vapor through large distances and its uniform application to large-area emitting surfaces in high-power sources of negative hydrogen ions.

We present the design analysis of a point focused electron beam emitter using numerical techniques. Simulation and modeling were performed followed by the calculation of emission parameters using programming codes EGUN and CST-PS. Beam emittance, average current density and perveance were calculated and are in agreement with the experimental values obtained at 10 kV acceleration potential. The emission parameters were evaluated up to 110 kV. This confirms possibilities of potential application of emitter for a linear accelerator.

It is proposed to combine the optical analyzer technique (OAT) and multiply photon Doppler velocimetry (MPDV) in every explosive experiment in order to overcome the reported discrepancies in the sound velocities measured in shock-compressed metals using different techniques. Such a combination is demonstrated to be efficient in explosive experiments with stepped samples of 12Kh18N10Т austenitic stainless steel and high-purity Mg95 magnesium under their shock-wave loading in ranges of 60–120 and 20–30 GPa, respectively. The OAT ensures classical recording of the longitudinal and bulk sound velocities. Depending on the loading intensity, the MPDV technique recorded temporal changes in the velocity of the “sample–indicator” interface or temporal changes in the shock-front velocity in the indicator. These data were used to monitor the parameters of the shock-compressed sample and to determine the instant when the first characteristic of the rarefaction-wave fan overtakes the shock-wave front in the indicator. Within the range of relatively low loads where the indicating fluid remains transparent and acts as a window material, the MPDV registers temporal variations in the velocity of the “sample–indicator material” interface. The OAT ensures reliable registration in the range of high-intensity loads, while the MPDV ensures time-resolved registration of the steady-shock-wave front velocity in the indicator up to the instant of its overtaking by a rarefaction wave. Both techniques are observed to work well in the intermediate range of loads. Combining these techniques enhanced the reliability of the obtained consistent data on the sound velocities in shock-compressed structural materials and also allowed a decreased number of explosive experiments with samples of toxic materials.

A high-pressure chamber designed to carry out various experiments under a pressure of up to 10 MPa at a temperature of up to 1600°C is described. The use of a ring connector ensures the quick connection of the upper lid and the bottom to the chamber body, the flanges of which are equipped with fast shutters. This joint makes it possible to substantially reduce the overall dimensions and the weight of the flanges of the chamber body and to mechanize the lid opening and closure operations, as well as to provide the required strength, tightness, and reliability of the joint.

A single-crystal diamond detector for the neutral-particle analyzer of the ITER project has been tested in proton and α-particle beams that were obtained using a heavy-ion accelerator. The use of a diamond detector as a particle analyzer seems to be promising because of its unique properties, such as operability at a high temperature and a high level of radiation resistance. The energy resolution of the detector and the minimum detectable particle energy have been determined.

An instrumental package for monitoring hydrophysical processes (internal and surface gravity waves, including tides, seiches, and wind waves) in the shallow part of the ocean shelf is described as well as methods and approaches.

A technique for evaluating the ultrasound-radiation intensity of medical equipment in continuous, pulse, and focused modes at any spatial point, which is based on the influence of the ultrasonic-wave radiation pressure force on small targets in the form of a set of gas bubbles in a liquid, is substantiated theoretically and a device is proposed. The results of the implementation of the developed technique for evaluating the intensity of therapeutic equipment are presented.

Some questions on the theory of charging particles in the charging chamber of an injector are considered. Two mechanisms (contact and contactless) for charging conducting particles in the region of the charging needle of an injector and the processes of charging microparticles by dark currents are considered. The value of the particle charge that is formed upon the occurrence of a microdischarge between the particle surface and the charging needle is evaluated. The results of the experimental study of the injector operation are presented: the plots that describe the dependence of the particle-escape frequency on the voltage at the charging electrode and the particle flow as a function of the diameter of the injector output aperture.

The present article portrays a design and implementation of microcontroller based system for displacement measurement using strain gauge based displacement sensor. A displacement transducer may be capacitive or resistive, is an uncontrollable device. Improvement in filtering increases the speed of measurement and enhances the measurement accuracy. In this paper a new algorithm and architecture is proposed as filter for the displacement measuring system with strain gauge based displacement sensor. We verify and implement the novel algorithm with this displacement transducer in the measuring of displacement successfully.

In this review, it is shown that out of the 300 scintillators synthesized to date only LaBr₃:Ce, CeBr₃, YAlO₃: Ce, and CsI:Tl crystals with the corresponding silicon photosensors (SiPSs) can be used as detectors in industrial γ-ray spectrometers intended for nuclear power plants. They are superior in their energy resolution and their resistance to mechanical and electromagnetic effects to spectrometers used today with a NaI:Tl crystal and a photomultiplier tube (PMT). A p–i–n photodiode (PD), an avalanche photodiode (APD), and a silicon photomultiplier (SiPM) are promising SiPSs. The properties of various assemblies of listed scintillators and photosensors are analyzed. A PD matches well with any scintillator. A spectrometer does not require LED stabilization of the scale, but its noise level must be reduced by selective PD cooling and the use of a light guide for coupling a massive scintillator and a SiPS with a small area of its sensitive surface. A spectrometer with an APD does not require photosensor cooling; however, LED stabilization of its energy scale is necessary. Application of an SiPM can rule out the use of a light concentrator (which is important for large CsI:Tl scintillators) and selective cooling, but this introduces nonlinearity at a short decay time and a high light yield in the scintillator (LaBr₃:Ce and CeBr₃) and also calls for an LED stabilization system for the spectrometer. The prospects for the development and application of new scintillation γ-ray spectrometers are discussed in this review.

Experimental investigations have shown that a timing device based on a constant-fraction discriminator is capable of providing a time resolution of approximately 0.5 ns and a timing error of approximately ±0.25 ns in the energy range of 0.8−1.8 GeV. In the region of “low” energies (<0.6 GeV), the time resolution is decreased by the influence of detector noise, whose level is ~3–5 mV for most scintillation detectors under investigation.

The use of S12572 MPPC silicon photomultipliers (Hamamatsu) for improving the timing characteristics of the PHOS electromagnetic calorimeter in the ALICE experiment at CERN is described. It is shown that by introducing an additional photodetector, that is, a silicon photomultiplier, it is possible, without worsening the energy resolution, to significantly improve the time resolution of the PHOS spectrometer from the current values of 3–4 ns to 150–200 ps.

The data-acquisition system of a muon tomograph based on the on-chamber electronics is described. Its advantages over the previously used system based on the electronics made to the VME-9U standard are considered. The hardware component and the software of the new data-acquisition system are presented.