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The technology for manufacturing large size shielded metal-ceramic cold cathodes is described. It has been shown that the use of a shielded metal-ceramic cathode allows to significantly increase the impedance of the vacuum diode and to form an electron beam of constant cross-sectional size or of the required size (up to 400 mm wide) with a fairly uniform electron beam current density distribution (≤15%). It has been found that the emission decline of the shielded metal-ceramic cathode, like that of the metal-dielectric cathode operating at a high repetition rate (≥100 pps), is significant at the beginning of the process and then slows down, allowing continuous operation for up to 40 h. Both cathodes require periodic cleaning of the plates, which is more difficult for metal-ceramic plates. At the same time, a metal-ceramic cathode works better at low vacuum, allowing twice as much current to be generated (in the same geometry) as a metal-dielectric cathode, while reducing the accelerating voltage by ∼15%. However, metal-ceramic plates are about 100 times more expensive to manufacture than dielectric plates for a metal-dielectric cathode. Therefore, the choice of cathode type for vacuum diode accelerators is not a trivial problem, but depends on many factors that must be taken into account in each case and for each radiation technology. • A shielded cathode has been designed to produce an electron beam with a cross-section of up to 400 mm. • It is possible to have a fairly uniform electron beam current density distribution (≤15%). • The beam size of the shielded metal-ceramic cathode can be practically constant. • The shielded metal-ceramic cathode works better at low vacuum than a metal-dielectric cathode. [ABSTRACT FROM AUTHOR]

Frequency nanosecond electron accelerators type URT has been developed for use in radiation technologies. The accelerator includes a thyratron, a pulse transformer and a semiconductor opening switch. The accelerating voltage is up to 0.9 MV, FWHM pulse length is up to 60 ns, and the repetition rate is up to 250 Hz. A metal ceramic cathode, which is used in the accelerator, provides an electron beam cross section up to 16 cm in diameter or rectangular with the dimensions of 45 * 5cm2at a maximum density of the pulse current equal to 2 A/cm2. Thus, a family of nanosecond electron accelerators has been developed for use in radiation technologies applied to layers up to 0.4 g/cm2thick, such as production of nanopowders from gas and liquid precursors. Experiments on the irradiation of silver nitrate solutions in various liquids by a URT-0.5 accelerator facilitated the development of technology for producing silver nanopowders (NPs). The powder yield and particle size as a function of the irradiation mode has been established. An increase in the adsorbed dose results in an increased powder yield; however, the particle size decreases and the powder agglomeration rate increases. Therefore, the targeted production of silver NPs with a mean particle size in the range of 90–1100 nm is possible. Besides to produce TiO2and SiO2NPs the gas precursors were used. [ABSTRACT FROM AUTHOR]

The development of radiation processing methods for food and agricultural products increases the demand for methods of control over the processing and circulation of products. ESR spectrometry is a promising method for monitoring and detecting, which is already being used to control products containing bones, cellulose and crystalline sugar. This research presents the results of a study of the radiation-induced ESR signal in eggshells and the kinetics of radicals over time. The samples were irradiated using the URT-0.5 (0.5 MeV) and UELR-10-10S2 (10 MeV) electron accelerators. The ESR signal spectra were obtained on an ELEXSYSE500 ESR spectrometer. The dependencies of the ESR signal intensity on the value of the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was carried out. • The samples were irradiated using the URT-0.5 (0.5 MeV) and UELR-10-10S2 (10 MeV) electron accelerators. • ESR signal was measured at ELEXSYSE500 ESR spectrometer. • The dependences of the ESR signal intensity on the absorbed dose in eggshell were obtained in the range from 1 to 40 kGy. [ABSTRACT FROM AUTHOR]

A vacuum diode for the two-sided electron irradiation of objects makes it possible to reduce the irradiation nonuniformity and increase the thickness of the irradiated layer of the object with a uniform distribution of the absorbed dose over the layer thickness. The cathode holder of the diode is constructed in the form of two symmetrical arms connected to a common current lead. Two cathodes are attached to the arms' ends opposite each other. The electron beam is extracted to the atmosphere through two windows–anodes positioned across from one another. The vacuum diode with metal–dielectric cathodes was tested on a УРТ-0.5 nanosecond electron accelerator (the electron energy is ∼0.5 MeV and the output beam power is ∼1 kW). The results obtained have shown that the diode ensures the two-sided irradiation of objects. Depending on the irradiated surface, the irradiation conditions can be varied by changing the cathode–anode distance in one of the arms of the diode. [ABSTRACT FROM AUTHOR]

Radiation processing applications for food and agricultural products require to control the applied doses values. This investigation shows the potential of using electron paramagnetic resonance (EPR) spectrometry for dosimetric control of wheat seeds irradiated at the URT-0.5 (0.5 MeV) linear electron accelerator. The general view of the wheat EPR spectra in the dose range 0–20 kGy is presented. The temporal kinetics of the entire spectrum and separated peaks has been studied. The EPR signal integral intensity dependences on the absorbed dose were obtained. • Wheat seeds were irradiated at electron accelerator URT-0.5 with 500 keV beam energy. • The EPR signal was evaluated to identify processing by low energy electron beam. • The dependences of the EPR signal on the absorbed dose in wheat seeds were obtained in the range from 1 to 20.4 kGy. [ABSTRACT FROM AUTHOR]