A two-stage method is proposed for controlling the regulators in the fuel burnup process during a single operating period. At the first stage, the coefficient of the heat release irregularity at the initial time moment is minimized; at the second stage, the instability criterion for a specified time interval is minimized. The linear interpolation of the neutron flux constructed on the basis of perturbation theory is considered to improve the calculation accuracy without high computational costs.

The effect of high-current relativistic electron beams on samples made of polycrystalline tungsten (Goodfellow) and corrosion-resistant ferrite-martensitic steel EK-181 was studied experimentally. In the experiments, a combined (molybdenum and steel) cathode was used, which made it possible to minimize the deposition of the cathode plasma on the materials under study. The experiments were carried out on a Kalmar high-current electron accelerator with an average pulse energy of E ≈ 100 J. A series of 1, 3, 6, and 10 pulses of accelerator operation were carried out for each material. The dependences of the ablation on the number of pulses were obtained. The microscopic examination of irradiated samples was carried out mass.

The currently existing macroscopic theories of scintillation spectrometers with a single photodetector have a number of fundamental drawbacks. The drawbacks can be overcome by a correct microscopic description of the processes occurring when the energy of the primary particle is converted into an output signal of the scintillation spectrometer. The mathematical model formulated in this work is the basis for the standard theory of scintillation spectrometers with a single photodetector, which allows one to obtain expressions for arbitrary moments of the signal distribution function at the output of the scintillation spectrometer. It is shown that the developed standard theory of scintillation spectrometers with a single photodetector does not have the drawbacks of other theories of scintillation spectrometers. In particular, the contribution to the energy resolution associated with the light yield nonlinearity of the scintillator is considered in the developed standard theory.

The paper briefly describes a modification to the simple iteration method as applied to the system of nonstationary spectral radiative heat transfer equations in kinetic model. The modification involves an additional stage where the integral intensity is adjusted on the basis of information accumulated at earlier stage of kinetic equation calculation. This allows us to more accurately consider how the solution evolves and thus improve convergence of iterations. As an illustration, results of two test problems in slab geometry are provided.

In this paper, we propose a method for calculating multiple scattering of ions when passing through thin layers of titanium deuteride in the form of a sum of three Gaussian distributions, the dispersions of which are compared with increasing layer thickness and the found form of the angular distribution of multiple scattering is reduced to a single Gaussian distribution. When calculating single Rutherford scattering, we used only scattering without knocking out of the target atom from the crystal lattice. Scattering with the knocking out of the target atom from the lattice was taken into account by discrete elastic scattering.

The contemporary composite high-temperature superconducting tapes (HTS tapes) are an advanced material for development of systems based on magnetic levitation. Development of levitation systems requires awareness on information on the effect of various external factors on levitation characteristics of the tapes. One of these factors is external mechanical pressure. For comprehension of the processes of deterioration of transport and levitation characteristics originating under mechanical loads on the stacks of composite HTS tapes, the effect of pressure on the critical current and levitation properties of the HTS tapes was investigated. The compression took place in the direction perpendicular to the plane of tape. The pressure varied from 0 Pa to 695 MPa, which corresponded to the force of impact of 10 kN on the stack of fragments of HTS tapes of 12 × 12 mm². The measurements of critical current on applied pressure both for individual tapes and for the stacks of three and five tapes were carried out. Also, the investigation of effect of compression on the levitation force of the stack of 50 tapes was carried out. The theoretical model based on the finite element method implemented with use of the Comsol Multiphysics software package was developed to analyze the obtained experimental results. On the basis of the evidence found, it can be inferred that, at uniform compression of an individual tape and stacks of tapes with small thickness (up to five tapes), deterioration of characteristics of the HTS tape takes place mainly at the boundary of the area of influence, owing to existence of bending deformation. Deterioration of the critical current and levitation force of the HTS tapes under pressures to 695 MPa was not found outside the boundaries of the impact. However, at compression of large stacks of tapes (50 units), though a boundary of compression is absent, inhomogeneous deformation of the layers of the tape proceeds, which can be produced by local flexural deformations determined by fluctuations of both shape of the tapes and thickness of the layers in individual tapes. This is responsible for a linear decrease in the levitation force with increase in pressure.

EuPRAXIA@SPARC_LAB [1, 2] will make available at LNF a unique combination offering three different options: a high-brightness electron beam with 1 GeV energy generated in a novel X-band RF linac; a PW-class laser system; a compact light source directly driven by a plasma accelerator. Plasma and conventional RF linac driven FEL provide beam with parameters of 30–200 pC charge range, 10–100 Hz repetition rate, and 1 GeV electron energy. The control of the charge and the trajectory monitoring at a few picocoulomb and a few micrometers is mandatory in this machine. Particularly in the plasma interaction region, where the pickup resolution under 1 μm is required. As a possible solution, a cavity beam position monitor (cBPM) is proposed [3]. A prototype in the C-band frequency range has been designed. The pickup was optimized for low charge and single-shot bunches to meet the project requirements. Here is presented the process to achieve the required specifications. The simulations were performed to study RF properties and the electromagnetic response of the device.

Impedances of the NICA collider ring elements have been simulated to minimize them to the values ensuring beam stability. To this end, the structure of the elements is changed by installing additional shields, removing resonating cavities, etc. On the basis of the numerical simulation, analytical calculations are performed for the region of stability of beam dynamics.

The feasibility of manipulating the beam polarization axis in a spin-transparent storage ring by means of spin-navigating solenoids has been investigated. In particular, deuteron beam spin dynamics in the given lattice and the lattice’s properties with respect to beam depolarization via spin decoherence have been considered.

This paper presents a description of the magnetic system of the developed electron cyclotron resonance (ECR) ion source with an operating frequency of 2.45 GHz for producing protons and doubly charged helium ions. The results of numerical simulations of the magnetic system of the ECR source built on permanent magnets are presented. A configuration with the possibility of moving the ring magnets of the injection and extraction area to adjust the magnetic field distribution, in particular, the maximum values of B_inj and B_ext at the plasma chamber axis, and with the possibility of moving the bars of the sextupole magnet in the radial direction to adjust the magnetic field B_rad at the chamber boundary is presented. To obtain the magnetic field profile corresponding to the mode of the microwave source, the design of the magnetic system with the use of additional solenoids providing adjustment of B_inj and B_ext values within the required limits as well as adjustment of the minimum magnetic field B_min on the chamber axis at fixed position of all ring magnets is considered.

We studied the process of switching a short vacuum gap, initiated by an auxiliary discharge along the surface of the dielectric by registration images using an electro–optical system. Based on the analysis of the results obtained, it was suggested that the emission of radiation and electrons from the cathode torch plays a significant role in the formation of the current channel in the discharge, which has been experimentally confirmed.

Results are presented of the determination of the temperature of the surface of powders in experiments on plasmachemical synthesis of micro- and nanosize structures in the mixtures of aluminum oxide Al₂O₃ and palladium Pd with different palladium concentrations. The obtained estimates of surface temperature (3100–2400 K) are between the melt and boiling points at atmospheric pressure of the components of the powder mixture Al₂O₃ and Pd, which creates suitable conditions for the ignition of self-sustained (chain) plasmachemical reactions.

Using the improved method of single Langmuir probes, the electron energy distribution functions (EEDF) were obtained in a short (10 mm) discharge gap between a rectangular hollow cathode and a mesh anode. It was found that the electron distributions are not Maxwellian with an excess of high-energy electrons (10–20 eV), the proportion of which decreases with distance from the cathode. The features are associated with the nonlocal mechanism of the EEDF formation.

Results of fundamental studies of the process for dynamic failure and dispersion of metals in the mode of pulsed volume heat-up under the action of penetrating rays allows the universal sinergetic attributes of metals behavior in the dynamic failure process, what supplies a capability to predict the unstudied metals behavior, involving actinide metals under extreme conditions. Determination of common relaxation attributes for non-equilibrium systems of various natures allows forecasting of non-studied systems behavior. Systematic studies of properties for plutonium metal (both native, as well as foreign ones) performed recently, allows reveal of ageing processes for plutonium metal, leading to some change of its physical-mechanical properties. The rate of these changes is rather low, and provide the process stability without a change of homogeneity, in the foreseeable future, would not result in a significant properties change. Estimates show, that α and fission-fragment activity weakly affect thermodynamic potentials (enthalpy, internal energy) of actinides for the normal and elevated temperatures T ~ 600 К. Actinide metals ageing processes, related to α and fission-fragment activity affect weakly the dynamic properties.

It was shown with the help one-, two-, and three-dimensional spectrometry that the excursion in the sequences of counts k(Δt) of alpha-particle fluxes of source ²³⁸Pu are accidental, do not have any periodic component, and the distributions of all emission values corresponds to the Poisson flow model.