S. Yu. Sokovnin

High-current electron beam generation by a metal–ceramic cathode

We present results of the investigation of a metal–ceramic cathode suitable for technological applications. The cathode was tested in electron diodes powered by two different high-voltage generators (500 kV, 50 ns, 300 Ω, ⩽200 Hz and 300 kV, 250 ns, 84 Ω, ⩽5 Hz). The metal–ceramic cathode which was made in a form of a disk was composed of TiO2 ceramics with stainless steel spherical particles uniformly inserted inside. It was shown that already at relatively low accelerating fields (E⩽5 kV/cm) fast cathode plasma formation occurs as a result of surface flashover. This surface flashover is initiated in triple points located in micropores which were formed during the process of cathode preparation due to the different thermal expansion coefficients of the ceramic and the metal. Experimental data concerning the uniformity of the light emission from the cathode surface and inside the anode–cathode gap and divergence of the generated electron beams are presented. Also, it is shown that the uniformity of the ge...

Production of ZnO and Zn-ZnO nanopowders using evaporation by a pulsed electron beam in low-pressure gas

This paper describes a method for the production of ZnO and Zn-ZnO nanopowders (NPs) using the evaporation of a target by a pulsed electron beam in a low-pressure gas and condensation on a cold crystallizer. Crystalline and amorphous NPs of pure ZnO and a Zn-ZnO mixture have been synthesized. These powders have a specific surface of up to 40 m2/g and are produced at a rate as high as 5 g/hour. It has been found that the pressure and the composition of gases (air, oxygen, and argon) in the evaporation chamber of the installation influenced the composition and the morphology of the powders. The effect that the target composition has on the production rate and characteristics of the powders has been studied. All the synthesized powders possessed marked magnetic properties.

YPT-0.5 repetitive-pulse nanosecond electron accelerator

An YPT-0.5 repetive-pulse nanosecond electron accelerator designed according to the thyratron-pulse transformer-semiconductor opening switch scheme is described. Its accelerating voltage reaches 0.5 MV, the FWHM pulse duration is 50 ns, and the pulse repetition rate is 200 Hz. A metal-dielectric cathode allows for obtaining an electron beam with a diameter of 30–100 mm at a maximum pulse current density of 40 A/cm2. Operating in the bremsstrahlung generator mode, the accelerator provides an absorbed dose rate of 30.4 Gy/min at a distance of 5 cm from the target.

Properties of the Amorphous-Nanocrystalline Gd 2 O 3 Powder Prepared by Pulsed Electron Beam Evaporation

An amorphous-nanocrystalline Gd2O3 powder with a specific surface area of 155 m2/g has been prepared using pulsed electron beam evaporation in vacuum. The nanopowder consists of 20- to 500-nm agglomerates formed by crystalline nanoparticles (3–12 nm in diameter) connected by amorphous-nanocrystalline strands. At room temperature, the Gd2O3 nanopowder exhibits a paramagnetic behavior. The phase transformations occurring in the powder have been investigated using differential scanning calorimetry and thermogravimetry (40–1400°C). The amorphous phase of the nanopowder is thermally stable up to a temperature of 1080°C. It has been found that the amorphous phase has an inhibitory effect on the temperature of the polymorphic transformation from the cubic phase into the monoclinic phase. It has been revealed that, compared with the microcrystalline powder, the Gd2O3 nanopowder is characterized by a complete quenching of photoluminescence.

Magnetic properties of oxide nanopowders obtained by pulsed electron beam evaporation

The magnetic properties of oxide nanopowders obtained by pulsed electron beam evaporation of targets in a low-pressure gas phase have been studied. Using this method, we obtained Zn-ZnO and ZnO nanopowders with the specific magnetization amounting to 2.8 × 10−2 and 2 G cm3/g, respectively. Significant room-temperature ferromagnetism has been observed for the fist time in a nanopowder of yttria-stabilized zirconia, where the specific magnetization reached ∼6.7 × 10−2 G cm3/g.

Effect of Iron Doping on the Properties of Nanopowders and Coatings on the Basis of Al 2 O 3 Produced by Pulsed Electron Beam Evaporation

Multiphase nanopowders (NPs) and amorphous/amorphous-nanocrystalline coatings (A-NC) have been prepared by the evaporation of ceramic targets of Al2O3-Fe2O3 (0.1, 3, 5 Fe2O3 mass %) by a pulsed electron beam in vacuum. The specific surface area of NP Al2O3-Fe2O3 reached 277 m2/g. The α and γ phases Al2O3 and other nonidentified phases have been found in the composition of NP Al2O3-Fe2O3. All coatings contained an insignificant fraction of the crystalline γ phase. No secondary phases on the basis of iron have been revealed. According to transmission electron microscopy, the fine fraction of NP Al2O3-Fe2O3 consists of amorphous nanoparticles of an irregular and quasispherical shape no more than 10 nm in size which form agglomerates reaching 1.5 μm. A large fraction of NPs consists of crystal spherical nanoparticles with preferential sizes of about 10–20 nm. All NP Al2O3-Fe2O3 showed ferromagnetic behavior at room temperature. The maximum magnetic response has been established in NPs with a minimum iron content (1.1 mass %). The pulsed cathode luminescence spectra of coatings and NP Al2O3-Fe2O3 have been presented by a wide band in the wavelength range of 300–900 nm regardless of their phase composition. Phase transformations into NP AL2O3-1.1% Fe and coatings from undoped Al2O3 heated to 1400°C occur according to the following scheme: amorphous phase → γ → δ → θ → α, regardless of their initial phase composition. The threshold of thermal stability of the Γ phase in NPs and the coating of undoped Al2O3 does not exceed 830°C. For the first time, the increased thermo and optically stimulated luminescent response comparable with the response of the leading TLD-500K thermoluminescent dosimeter has been reached in A-NC coatings of undoped Al2O3.

Investigation of properties of ZnO-Zn-Cu nanopowders obtained by pulsed electron evaporation

ZnO-Zn and ZnO-Zn-Cu nanopowders with a high specific surface (up to 68 m2/g) is obtained by pulsed electron evaporation. The characteristics of nanopowders (NPs) are investigated by X-ray phase analysis (RPA), high-resolution transmission electron microscopy (HR TEM), electron diffraction analysis, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, inductively coupled plasma (ICP) method, and pulsed cathodoluminescence (PCL). For the first time, ferromagnetism at room temperature is found in ZnO-Zn-Cu nanopowders. The powder magnetism is connected with defects and magnetic Cu2+ ions in amorphous interlayers at interfaces between ZnO nanocrystallites. The connection of magnetic properties of nanopowders with the lattice constant of the fine-crystalline fraction of ZnO is shown.

Production and studies of properties of nanopowders on the basis of CeO2

Nanopowders (NPds) of pure CeO2 of a specific surface area up to 210 m2/g and those doped with copper, carbon, and iron (≤1 wt % of dopant) of a specific surface area in the range 130–160 m2/g have been produced by evaporation with a pulsed electron beam. According to the X-ray phase analysis data, no secondary phases (aside from the cubic CeO2 phase) were found in the produced NPds. All the powders contained fine- and coarse-crystalline fractions differing in the size of their coherent scattering region (CSR) and in their amorphous component. The degree of crystallinity of the powders was not above 22%. The powders have a fractal structure and consist of agglomerates of sizes from dozens to hundreds of nanometers formed by crystalline nanoparticles (NPts) 3–5 nm in size with a very narrow particle size distribution. NPds have a high structural defectiveness degree, which was reflected in their magnetic properties. The room ferromagnetism was established in NPds of pure CeO2 − x and those doped with nonmagnetic elements (carbon and copper): here the ferromagnetic state in the CeO2-C system was established for the first time, whereas the magnetic moment on the carbon atom was 35-fold lower than the theoretical estimation. The ferromagnetic contribution to CeO2 NPd increases with a decrease in the NPt size and reaches 0.1 emu/g in CeO2-Fe NPd (xFe = 0.54 wt %). It has been established that there is no direct dependence between magnetization and the content of iron ions in the CeO2-Fe-based NPds.

A review of possible applications of nanosecond electron beams for sterilization in industrial poultry farming

Elaboration of principles of technologies for radiation sterilization employing nanosecond electron accelerators in the industrial poultry farming was studied. The obtained results suggest that the URT-0.5 accelerator may be used to sterilize a bone meal. It is possible to create the processing line providing an output of 1500 kg per hour at the estimated cost amounting to

Application of nanosecond electron beam for production of silver nanopowders

0.01/kg. Was found that consumer properties of the melange changed little up to an absorbed dose of 50 kGy and approached the measurement error. So, it is possible to use the URT-0.5 accelerator as the basis of a process line with an output of about 800 l/h at the estimated cost of nearly 0.14