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Volume 87, Nº 5 (2024)
ЯДРА. Эксперимент
MEASUREMENT OF THE RATES OF THE 102Pd(𝑛, γ)103Pd AND 102Ru(𝑛, γ)103Ru REACTIONS IN THE HORIZONTAL CHANNEL OF THE IR-8 REACTOR AT NRC “KURCHATOV INSTITUTE”
Resumo
Metastasis is one of the main causes of relapse and subsequent high mortality from cancer. Metastases can contain very few cells and spread throughout the body. Despite the existing variety of diagnostic imaging methods, in practice, the resolution of none of them allows one to unambiguously diagnose the presence of a tumor (clump of cancer cells) smaller than 1–2 mm in size. After surgery and tumor removal, patients are typically offered chemotherapy, external beam radiation therapy, or α- or β-emitter radionuclide therapy. This therapy has side effects that lead to additional risks and may interfere with continued treatment. Recently, a number of works, in contrast to the traditional approach, have proposed using “short-range” radionuclides instead of α- or β-emitters [1–3]. It is convenient to use Auger or conversion electron emitters as “short-acting” therapeutic agents. Auger electrons and conversion electrons have a short range and high specific linear energy loss in biological tissue; they are capable of damaging cells within a few tens of microns, but do not have a radiotoxic effect over l ng distances, without damaging healthy cells and tissues. The most efficient and convenient Auger and conversion electron emitters for practical use include 103mRh (𝑇1/2 = = 56.1 min), which has the lowest ratio of the number of γ quanta to electrons [1] and can be obtained by a generator method. The predecessors of 103mRh (𝑇1/2 = 56.1 min) in the generator can be 103Ru (𝑇1/2 = = 39.247 days) or 103Pd (𝑇1/2 = 16.99 days). In order to clarify the prospects for producing these precursors, we have measured the rates of reactions 102Ru(𝑛, γ)103Ru and 102Pd(𝑛, γ)103Pd upon neutron irradiation of metal ruthenium of natural isotopic composition and metal palladium, enriched in the 102Pd isotope to 96.36%, in a horizontal experimental channel of the IR-8 reactor.
Âdernaâ fizika. 2024;87(5):365-368
365-368
PHOTONEUTRON REACTION CROSS SECTIONS FOR 90Zr IN DIFFERENT EXPERIMENTS
Resumo
Reliability of the data on partial photoneutron reactions on 90Zr obtained in the experiment carried out on the beam of bremsstrahlung was investigated using the experimental-theoretical method for partial reaction cross section evaluation basing on objective physical criteria. It was found out that (γ, 1𝑛) and (γ, 2𝑛) reaction cross sections obtained using the corrections calculated via statistical theory to the neutron yield cross section σ(γ, 𝑥𝑛) = σ(γ, 1𝑛) + 2σ(γ, 2𝑛) satisfy physical criteria of data reliability. The integrated characteristics of the cross sections of the reactions (γ, 1𝑛) and (γ, 2𝑛) in which the distinct structural features were obtained as well as in the experimentally measured neutron yield cross section σ(γ, 𝑥𝑛) agree with those of evaluated cross sections. This shows that information on 90Zr partial reactions competition obtained using statistical theory satisfies physical criteria of data reliability. The evaluated reaction cross sections are compared in detail with analogous data obtained before using the results of experiments carried out on the beams of quasimonoenergetic annihilation photons.
Âdernaâ fizika. 2024;87(5):369-381
369-381
ЯДРА. Теория
TWO-PHOTON RESONANCE MECHANISM OF OPTICAL PUMPING OF THE 8.3-eV ISOMER 229mTh IN NEUTRAL ATOMS
Resumo
The possibility of refining the energy of the nuclear isomer 229mTh with the energy of 8.36 eV, the most likely candidate for the role of a nuclear frequency standard, using resonant optical pumping is discussed. Attention is focused on the broadening of theresonance in order toreduce scanning time. The proposed twophoton method uses radical broadening of the isomer line due to mixing with an electronic transition. This method is not burdened by cross-section reduction, in contrast with internal-conversion-based resonance broadening or intended extra-broadening of the spectral line of a scanning laser. In the case under consideration, it turns out to be two orders of magnitude more effective. It applies to both ionized and neutral thorium atoms. The realization of the method supposes excitation of both the nucleus and the electron shell in the final state.
Âdernaâ fizika. 2024;87(5):382-389
382-389
ЭЛЕМЕНТАРНЫЕ ЧАСТИЦЫ И ПОЛЯ. Эксперимент
INVESTIGATION OF HIGH-ENERGY NEUTRINOS AT THE LARGE HADRON COLLIDER
Resumo
The first neutrinos from the proton-proton collisions at an energy of 13.6 TeV were registered in the pseudorapidity range of 7.2 > η > 8.4 in the SND@LHC experiment at CERN. SND@LHC is an autonomous experiment based on a compact hybrid detector for detecting high-energy neutrinos at the Large Hadron Collider. The detector allows to distinguish the interactions of the neutrinos of all three flavors and to investigate the process of the charmed particles’ generation in the pseudorapidity region inaccessible to other experiments at the LHC. The aim of the experiment is also to study the scattering of weakly interacting particles on the electrons and protons of the target.
Âdernaâ fizika. 2024;87(5):390-399
390-399
CROSS SECTION OF THE PROCESS 𝑒+𝑒− → 𝑛𝑛 NEAR THE THRESHOLD
Resumo
The 𝑒+𝑒− → 𝑛𝑛 cross section was measured at energies from the threshold to 1908 MeV in the center of mass (c.m.). The experiment to measure the cross section has been carried out at the VEPP-2000 𝑒+𝑒− collider in 13 energy points. The SND detector is used to detect the produced neutron-antineutrons (𝑛𝑛) events. A special time measurement system on the calorimeter was used to select the time-delayed 𝑛𝑛 events. The measured 𝑒+𝑒− → 𝑛𝑛 cross section is 0.4–0.6 nb. The neutron effective timelike form factor in the energy range under study varies from 0.3 to 0.6.
Âdernaâ fizika. 2024;87(5):400-413
400-413
INVESTIGATION OF THE NEUTRINO CHANNEL AT THE U-70 ACCELERATOR COMPLEX WITH PARENT PARTICLE BEAM DEFLECTION
Resumo
Principle optical scheme of the neutrino beam production channel based on the accelerator complex U-70 is considered. In order to extract the required pulse interval of π-mesons, a two-magnetic system with a “field” lens with a one-way deflection of the parent particle beam and full compensation of the dispersion is proposed. In this scheme the decay part of the channel is deflected with respect to the direction of the primary proton beam aiming at the target. The main computational characteristics of the neutrino beam at the far detector at a distance of 2595 km from the end of the decaying part of the channel as well as the parameters of the parent π mesons at the beginning of the decaying part are discussed.
Âdernaâ fizika. 2024;87(5):414-420
414-420
THE USE OF A XENON GAMMA SPECTROMETER FOR DOSIMETRY IN BORON-NEUTRON CAPTURE THERAPY
Resumo
One of the main problems associated with the implementation of neutron capture therapy in clinical practice, requiring a solution, is the determination of absorbed dose. The only method that directly allows measuring the absorbed dose is gamma spectrometry, based on the registration of gamma rays with an energy of 478 keV. This article considers the possibility of using a xenon gamma spectrometer, which has high radiation resistance to neutron fluxes. The GEANT4 software package was used to study the neutron capture therapy process and conduct corresponding calculations.
Âdernaâ fizika. 2024;87(5):421-425
421-425
ЭЛЕМЕНТАРНЫЕ ЧАСТИЦЫ И ПОЛЯ. Теория
THE RARE 𝐷𝑠-MESONS’ DECAYS INTO THREE CHARGED LEPTONS AND NEUTRINOS IN THE FRAMEWORK OF STANDARD MODEL
Resumo
In the framework of the Standard Model, the values of branching ratios and differential distributions for four-lepton decays 𝐷𝑠− → µ+µ−¯ν𝑒 𝑒− and 𝐷𝑠− → 𝑒+𝑒−¯νµ µ− are found. In our calculations we took into account the processes of a virtual photon emission by 𝑠- and 𝑐-quarks of the 𝐷𝑠−-meson and bremsstrahlung. The emission of a virtual photon by 𝑠-quark have been described using the vector mesons dominance model.
Âdernaâ fizika. 2024;87(5):426-437
426-437
KLEIN–GORDON EQUATION, QUNTUM RELATIVISTIC HYDRODYNAMICS AND QUANTUM SHOCK WAVES IN DESCRIBING COLLISIONS OF ATOMIC NUCLEI
Resumo
In this work, the equations of quantum relativistic hydrodynamics are obtained from the effective Klein–Fock–Gordon equation taking into account dissipation. Taking into account dissipation in the Klein–Gordon equation leads to the need to introduce an additional thermal term and an equation for it. As a result, a closed system of equations was obtained taking into account non-equilibrium processes, which makes it possible to describe the dynamics of the process of collisions of atomic nuclei and calculate the yield of secondary particles. Solving the resulting equations makes it possible to identify quantum shock waves and the time evolution of the resulting hot spot. The calculated spectra of emitted protons in heavy ion collisions are compared with available experimental data.
Âdernaâ fizika. 2024;87(5):438-448
438-448