The possibility of using synthetic diamond crystals as a sensitive element of resistive-type thermal sensors developed to control target heating in a neutron generator is discussed. Information about the design and manufacturing technology of a mock-up sample of the temperature sensor, as well as data from an experimental study of its dynamic characteristics, are given. On the example of a neutron generator developed based on a high-current accelerating diode, a scheme for thermal control of a neutron-forming target is proposed.

We present the simulation results of a diode accelerator for generating neutrons with a laser source of deuterons and a system for suppressing electronic conductivity by the pulsed magnetic field of a spiral line. The possibility of implementing an effective pulsed neutron generator based on the accelerator is shown. The results of computer and physical experiments allow us to hope for the possibility of creating a sealed accelerating tube with output parameters above 10 10 n/pulse as a result of T (d, n) 4 He nuclear reactions. A possible design for such an accelerating tube is proposed, and the technological feasibility of its implementation is substantiated.

The article presents a new experimental portable pulsed neutron generator based on a laser-plasma ion diode with magnetic insulation and the results of the first experiments. The laser-plasma diode makes it possible to obtain large ion current pulses that generate high-intensity neutron radiation. The source of optical radiation was a pulsed neodymium-doped yttrium aluminum garnet laser with a wavelength of 1064 nm, a pulse energy of up to 0.7 J, and a duration of ~10 ns. The ion beam is accelerated by an Arkadiev-Marx pulsed voltage generator with a voltage amplitude of up to 250 kV, a duration of up to 1.5 µs, and an energy of up to 160 J. Neutrons were generated using the reaction d(d,n)3He. A neutron yield of 2·107 neutron/pulse was obtained.

The formation of ion fluxes of the laser plasma by axially symmetric magnetic fields is studied. An algorithm for forming ion fluxes is developed and a computer experiment is carried out. As a result of the computer and physical experiments, it is shown that ion packets with a duration exceeding several microseconds, which contain more than ~1012 particles at a flight distance of about 2 m, can be obtained at the output of a laser-plasma ion source.

The presence of peculiarities in terahertz spectra of many organic compounds allows the use of THz imaging and spectroscopy for the detection of various hazardous and explosive substances. This work is devoted to the study of the detection of trace amounts of 1,3,5-Trinitro-1,3,5-triazinane (RDX) in the form of particles localized in millimeter and submillimeter sizes using THz imaging with spectral resolution. As a result of the work, images of trace amounts of RDX in reflected THz radiation were obtained. The contrast in these images made it possible to detect single particles of the powdery substance. The difference in contrast for RDX and polyethylene (PE) in the obtained terahertz images makes it possible to use THz imaging with spectral resolution not only for detection, but also for the identification of chemical compounds.

This work reports on an advanced approach to the design of THz photoconductive. antenna (PCA). The LT-GaAs thin films used for the PCA fabrication were synthesized by MBE method on GaAs (100) substrate by adjusting the As pressure, As/Ga fluxes ratio, growth/annealing temperatures and annealing time. These parameters crucially affect electro-optical properties of the PCA samples as evidenced by the THz radiation power and time-domain spectroscopy measurements. The annealing temperature of 670 degrees C was found to be optimal for constructing a PCA possessing high amplitude of the THz radiation over the spectral range up to 1 THz at the resonance of 0.1 THz. The comparison of this PCA with the reference ZnTe crystal reveals a 2-fold increase in THz power. Furthermore, this antenna attains a 1.5-, 3-, and 2-fold increase in THz power, photocurrent efficiency, and actuating dc BV, as compared with the commercial ZOMEGA antenna. These results pave the way towards the creation of highly efficient LT-GaAs-based PCAs.

Abstract—The acceleration of a plasmoid, for the formation of which a conical spiral expanding in the direction of the expected plasma acceleration is used, in a rapidly increasing magnetic field of complex geometry has been considered. An algorithm for calculating the longitudinal magnetic field in the approximation of replacing a spiral line with a system of rings of variable radius has been presented. A mathematical model that is based on the interaction of the plasmoid magnetic moment with gradient of the longitudinal magnetic field decay has been proposed to analyze the efficiency of the acceleration. The possibility of deuterons reaching an average speed exceeding 10^6 m/s has been shown.

The acceleration of a plasmoid, for the formation of which a conical spiral expanding in the direction of the expected plasma acceleration is used, in a rapidly increasing magnetic field of complex geometry has been considered. An algorithm for calculating the longitudinal magnetic field in the approximation of replacing a spiral line with a system of rings of variable radius has been presented. A mathematical model that is based on the interaction of the plasmoid magnetic moment with gradient of the longitudinal magnetic field decay has been proposed to analyze the efficiency of the acceleration. The possibility of deuterons reaching an average speed exceeding 106 m/s has been shown.

In order to use neutron generators in applied research, it is important to increase the energy effi ciency of neutron generation. For high accelerating voltages, diodes with magnetic insulation are used to suppress electron emission from the cathode in neutron accelerator tubes. A mathematical model describing the dynamics of charged particles in the axial diode with insulation of electrons by the fi eld of a permanent magnet is studied. The model is used to perform a computer experiment that shows a reduction of insulation near the ends of the magnet, which permits up to 40% of the electrons from the cathode to reach the anode of the accelerator tube. An option for making the magnetic insulation more effi cient by adding into the magnetic system diaphragms placed in the end zones of a cylindrical cathode is proposed and studied.

The work is devoted to the influence of scattering of terahertz (THz) radiation by hexogen particles (RDX) in powdery samples on their transmission and reflection spectra. A terahertz radio-vision installation with spectral resolution was used to determine experimentally THz spectra of RDX. For samples with small RDX particles (the typical particle size is 100 μm), characteristic peaks at 0.8 THz and 1.06 THz are observed in absorption spectra despite scattering, that can be used to identify this substance. For large hexogen particles (a typical particle size is 450 μm), experiments and numerical simulation showed that even the most intense peak at 0.8 THz is not observed in absorption spectra, and the spectra are mainly due to the scattering effect and its depending on the wavelength of radiation. The reflection spectra of RDX layers (particle size is about 100 μm) qualitatively differ from the reflection spectra of RDX crystals and are formed as a result of absorption during propagation of THz radiation in the particle layer. Thus, the substance can be identified by absorption spectra in a reflection scheme.

AbstractLow-temperature gallium arsenide (LT-GaAs) films were grown by the method of molecularbeam epitaxy (MBE) at a reduced temperature (230°C) on GaAs(100) substrates and subjected to postgrowth annealing in various regimes. Photoconductive antennas (PCAs) with flag geometry formed on the film surface were characterized by terahertz (THz) response power at various bias voltages. The method of THz spectroscopy was used to study the characteristics of PCAs based on LT-GaAs films annealed in various regimes and the optimum interval of postgrowth annealing temperatures (670–720°C) was established.

The paper presents the results of application of terahertz radiation for detection of traces of explosives on surfaces of objects in reflected light. The process of detection and identification of explosives is based on a recording of interferograms of reflected radiation in spectral range of 0.5 -2.5 THz with help of a Michelson interferometer. The reverse Fourier processing lets to obtain reflection or transmittance spectra and images of objects. Spectral ranges for imaging are chosen by an operator. An installation elaborated for this purpose is described. Specific features of reflection spectra of some organic substances are determined.