A method for determining bone density based on a single exposure on a serial X-ray machine and subsequent calibration by a stepped aluminum wedge has been developed. The experimental setup is described, the results of measurement on the phantom are presented. During calibration, an effective subtraction of soft tissues was carried out. The results of comparison of experimental data with GEANT-4 simulation are presented. Estimates of the effect of uneven illumination, coordinate resolution and scattered background on the quality of the image are made. The conclusion is made about the competitiveness of the developed technique in comparison with traditional two-beam diagnostics.

The possibilities of studying the reaction yields of ^13 C (γ,p)^12 B, ^14 N (γ,2p)^12 B, and ^14 N (γ,2n)^12 N through measurements of induced ( ^12 B, ^12 N) activities with thin Δ E detector telescopes in temporal intervals between electron accelerator pulses have been analyzed. Estimates for the production of ( ^12 B, ^12 N) nuclei and registration of their decay are provided, taking into account the parameters of the electron beam, Ta radiator, irradiated targets made of graphite or NH _4 NO _3 , and telescopes of plastic scintillation Δ E detectors.

The issues are considered for studying the yields of the reactions 13C(γ, p)12B, 14N(γ, 2p)12B, and 14N(γ, 2n)12N with measuring (12B, 12N)-activity by telescopes of ΔE-detectors in time between electron accelerator pulses. For the chosen radiators and targets, the fluxes, and spectra of irradiating bremsstrahlung γ-quanta are found. The influence of the parameters of targets and telescopes of ΔE-detectors on production of (12B, 12N)-nuclei and registration of their decay is estimated.

The possibilities are analyzed for studying the yields of reactions 13C(𝛾, 𝑝) 12B, 14N(𝛾, 2𝑝) 12B, 14N(𝛾, 2𝑛) 12N by measuring the induced (12B, 12N)-activity with telescopes of thin Δ𝐸–detector in time intervals between electron accelerator pulses. For production of (12B, 12N)- nuclei and registration of their decay, estimates are given taking into account the parameters of the electron beam, Ta–radiator and irradiated targets made from graphite or NH4NO3, as well as the parameters of scintillation Δ𝐸 detector telescopes made from thin plastic plates.

The authors discuss problems of studying the yields of the reactions 13 C(γ, p ) 12 B, 14 N(γ, 2 p ) 12 B, and 14 N(γ, 2 n ) 12 N with ( 12 B, 12 N) activity measured by the telescopes of Δ E detectors in the intervals between electron accelerator pulses. The fluxes and spectra of irradiating bremsstrahlung γ-quanta are found for chosen radiators and targets. The effect the parameters of targets and telescopes of Δ E detectors have on the production of ( 12 B, 12 N) nuclei and the registration of their decay is estimated.

The transparency of the carbon nucleus with respect to eta mesons of energy 25 to 95 MeV was measured. Mesons of this energy originated from the photoproduction on quasifree protons of the carbon nucleus ( $$\gamma p\to\eta p$$ ) under the effect of photons with energies between 720 and 770 MeV. The inelastic cross sections for $$\eta N$$ interaction in nuclear matter are determined from the measured transparency of the nucleus. The absence of nucleon resonances in the measured cross section—in particular, the $$S_{11}$$ resonance, which is usually associated with the assumption of the existence of eta-meson nuclei—is discussed.

An experiment to study total nuclear photoabsorption cross sections at the linear electron accelerator LUE-8-5 (INR, RAS) in the photon energy region of 5–10 MeV called the pygmy resonance is simulated. The motivation for the experiment is new experimental data on photoexcitation of spin isomers of medium-heavy nuclei, which indirectly indicate a change in multipolarity of near-threshold photoabsorption of nuclei. The experiment implies direct investigation of the observed effects by measuring total photoabsorption cross sections in the photon beam. The simulation is performed using the GEANT-4 code. The parameters of the facility are optimized, and the choice of the detectors for the measurements is substantiated.

New experimental data on the multifragmentation of carbon nuclei that is initiated by the photoproduction of neutral pions and eta mesons are discussed. The novelty is associated with the exclusive character of the processes being studied, in which case a determination of partial meson-photoproduction reactions is followed by an analysis of complementary particles for coincidence. The experiment being discussed was performed by the GRAAL (GRenoble Accelerateur Anneau Laser) Collaboration in a beam of 500- to 1500-MeV Compton photons. The possibility of performing new experiments within the BGO-OD Collaboration (Bonn, Germany) is considered. A new method for studying the interaction of short-lived mesons with nuclei on the basis of detecting cascade recoil nucleons is proposed.

The results of experimental studies of positron generation near the threshold carried out in 2018 at the ILC MSU femtosecond laser complex and the LUE-8 linear electron accelerator of the Institute for Nuclear Research of the Russian Academy of Sciences are presented. The measurements were carried out using three different detection methods: using a MEDIPIX detector; phosphor films and video cameras; as well as scintillation arrays and silicon photomultipliers.

It is important for national security to control the movement of dangerous or strategically cargo such as explosives, radioactive materials, rare and precious metals. This control can be provided by scanning transport containers by gamma rays. In this report the existing technique for scanning (dual energy method) is considered and the alternative method based on measuring the energy distribution of gamma rays is proposed. For estimation perspectives of the proposing method, the corresponding simulation was conducted by using the GEANT4 toolkit. The example of the algorithm of reconstruction the chemical composition of the scanned object is also considered. In addition the experiment for estimation energy resolution of the detector based on a scintillation crystal BGO and SiPM was carried out.

A brief review of the works devoted to studying the photonuclear reactions near the threshold at the LUE-8.5 MeV linear electron accelerator of the Institute for Nuclear Research of the Russian Academy of Sciences and the terawatt femtosecond laser complex of the International Laser Center at Moscow State University is provided. The main focus of attention is the simulation of the experiments using the GEANT-4 code. This allowed us to compare the possibilities of different methods and determine the main directions of future research.

A procedure for measuring photonuclear-reaction cross sections by employing the method of quasimonochromatization of the bremsstrahlung photon spectrum is developed. This procedure permits determining reaction cross sections via measuring the reaction yield at three fixed values of the electron energy. The procedure is equivalent to measuring the cross section in question for quasimonochromatic photons. Bremsstrahlung-photon spectra are obtained using state-of-the-art simulation means involving the GEANT4 code as applied to a specific experiment with allowance for its geometry, target thicknesses, electron-beam parameters, etc. The results obtained by simulating quasimonochromatic distributions of bremsstrahlung photons are presented for experiments at the LUE-8-5 linear electron accelerator of Institute for Nuclear Research (Moscow, Russian Academy of Sciences). These results are found to be in good agreement with the experimental energy distribution of the cross section for the reaction 111Cd(γ, γ') in the energy range between 5 and 8 MeV.

New experimental results on photo-excitation of the Cd and In spin isomers by real and virtual photons (electrons) in the threshold energy region are presented. Measurements have been performed using the INR electron linac LUE-8 MeV and, in parallel, the femtosecond laser facility of the Moscow State University. A detailed description of experimental methods based on the GEANT-4 simulation is done. The obtained data are discussed in frame of the phenomenological model which allows the theoretical evaluation of the isomeric ratio in this energy region. Contribution of the dipole and quadrupole mode excitations in Cd and In nuclei from measurements with real and virtual photons is discussed.

A method for measuring the bremsstrahlung X-ray spectra of electrons accelerated in a laser plasma using Medipix matrices has been developed. The application of the matrix provides the spectrum accumulation in a much shorter time, as compared to detectors based on a scintillator and a photomultiplier commonly used for such measurements. This ensures dynamic monitoring of the X-ray characteristics and prompt adjustment of the laser source parameters to obtain the maximum X-ray yield and energy. The results of measurements of the X-ray spectra at the ILC MSU terawatt femtosecond-laser complex for various laser-plasma interaction regimes are presented.