Petersburg Nuclear Physics Institute Research Articles

Measurement of the Cross Section for the Neutron-Induced Fission of 237Np Nuclei in the Energy Range of 0.3–500 MeV

The cross section for the neutron-induced fission of 237Np nuclei in the neutron energy range of 0.3–500 MeV has been measured using the time-of-flight spectrometer of the GNEIS neutron complex at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute. The 237Np(n, f) fission cross section has been measured with respect to the 235U(n, f) fission cross section and fission fragments have been detected by low-pressure position-sensitive multiwire proportional counters. The data obtained have been compared to the previous experimental results and to estimates from various evaluated data libraries.

Evaluation of antihypoxic effects of therapeutic breathing mixtures with high argon content on the example of acute blood loss in laboratory animals: a preclinical randomized experimental study

Background. According to the hypothesis of the study, the therapeutic efficacy of measures to treat hypoxic (ischemic) emergencies can be significantly increased by using an artificial gas mixture with normal or increased oxygen content and a high content of argon, being bioactive despite its chemical inertness.Objective. To experimentally evaluate the antihypoxic effects of argon on the example of acute massive blood loss in experimental animals.Methods. The study was carried out on 72 albino male gray rats with a baseline body weight of 220–250 g. The experiments were performed at the premises of the Konstantinov St. Petersburg Nuclear Physics Institute of the Kurchatov Institute and the Smorodintsev Research Institute of Influenza (Russia). Prior to the experiment, the animals were quarantined for 2 weeks in the vivariums of the performing organizations. Acute massive blood loss in rats was formed by taking blood (12 ± 1% of body weight on average) using syringe method by transcutaneous cardiac puncture. Rats were randomized into 3 groups (24 individuals each) depending on the gaseous medium where the animal was placed after artificial blood loss. Composition of the applied gaseous medium in the comparison groups: medium No. 1 — oxygen 21% vol.; argon — 30% vol.; nitrogen — the rest; medium No. 2 — oxygen 21% vol.; argon — the rest; medium No. 3 (control) — air. The postoperative follow-up (post-conditioning) for 8 hours involved assessing and recording the following indicators: survival/lethality rates; recovery rates (anesthesia recovery, somatic mobilization); clinical symptoms of possible intoxication with the gas mixture during inhalation exposure. The surviving animals were then monitored for 4 days to evaluate their health and behavioral performance. Upon completing the observation period, the animals were euthanized.Results. After artificially-induced blood loss, all the non-survivors died within 1.5–8 hours after the operation. In group 1 (post-conditioning in medium No. 1), the lethality of laboratory animals amounted to 4 individuals out of 24 (16%); in group 2 (post-conditioning in medium No. 2) — 2 individuals out of 24 (8%). In the control group, the lethality rate was significantly higher — 10 animals out of 24 (42%). The surviving animals demonstrated no lethality or morbidity within 4 days after the exposure. Analysis of outcomes between experimental groups and controls revealed that the significance of differences in the lethality index between group 1 and control (by Fisher’s two-sided criterion) comprised p = 0.06; between group 2 and control — p = 0.017. When the statistical “power” of the experimental group was increased (by combining samples 1 and 2), the significance of differences in outcomes in this group compared to the control accounted for p < 0.001.Conclusion. The conducted studies confirmed the hypothesis about the pronounced antihypoxic effect of argon, which significantly increased the survival rate of experimental animals after massive artificially-induced blood loss.

Measurement of the Cross Section for the Neutron-Induced Fission of 238U Nuclei in the Energy Range of 0.3–500 MeV

The cross section for the neutron-induced fission of 238U nuclei has been measured using the time-of-flight spectrometer of the GNEIS neutron complex at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute, in the neutron energy range of 0.3–500 MeV. Fission fragments have been detected by low-pressure position-sensitive multiwire proportional counters. The cross section for 238U(n, f) fission has been measured with respect to the cross section for 235U(n, f) fission, which is an accepted international standard. Data on the energy dependence of the anisotropy of the angular distribution of fragments of neutron-induced 238U nuclei are also presented. The data obtained have been compared to previous experiments carried out using both similar and significantly different methods.

Development of UCN sources at PNPI

This article reviews the development of various sources for ultracold neutrons (UCNs) at the Petersburg Nuclear Physics Institute (PNPI). For 45 years, PNPI has proposed and manufactured cryogenic devices for neutron conversion to low energies. Based on beryllium, hydrogen and deuterium, they can be operated in the intense radiation fields near the core of a nuclear reactor. A more recently launched UCN source development utilizes superfluid helium (He-II) as conversion medium. Initially proposed and designed for PNPI’s old WWR-M reactor, the project has been reshaped to equip the institute’s PIK reactor with a modern UCN source of this type. The projected UCN density in the closed source chamber is 2.2 × 103 cm−3, which, as calculations of neutron transport show, will provide 200 cm−3 in the chambers of a neutron EDM spectrometer connected to the source by a UCN guide. Experiments at PNPI with a full-scale UCN source model have demonstrated that a heat load of 60 W can be removed from the He-II in the converter at a temperature of 1.37 K. This fact confirms the practical possibility to implement low-temperature converters under “in-pile” conditions with large heat inflows. The review concludes with a presentation of various proposed options for a He-II based UCN source at the European Spallation Source.

Development of molecular genetic technologies in Pavlov University: 20 years history and achievements

21 years have passed since the signing of the order on the establishment of the Department of Molecular Genetic Technologies of the Scientific Research Center (order № 118 was signed by Academic N. A. Yaitsky on June 5, 2001) and 20 years have passed since the beginning of the Department's activities. The leading scientist in the field of molecular medicine, Professor Evgeny Iosifovich Schwartz, not only headed the Department, but also brought there his team — the team of the Laboratory of Human Molecular Genetics of the Petersburg Nuclear Physics Institute named by B. P. Konstantinov of National Research Centre «Kurchatov Institute». The team was the first in the country to use the polymerase chain reaction (PCR) method to diagnose human hereditary diseases, and at that time had experience both in mapping mutational damage in monogenic human diseases and in its research in the field of multifactorial pathology. The department creation marked the beginning of molecular genetic technologies at the University and became the basis for fundamental scientific researches and the development of modern methods of molecular genetics. The review describes the history of Department and its main achievements.

JASPER: a software for quantum chromodynamics Dyson-Schwinger equation numerical calculation

The JASPER program is the first part of the high-performance computing information system for estimate some elementary particle properties, developing at Petersburg Nuclear Physics Institute. The JASPER is an implementation of the Dyson-Schwinger equation numerical solution for simple dressed quark propagator calculation in rainbow approximation. The Dyson-Schwinger equation solution with the Marice-Tandy Ansatz is one of several phenomenological approaches to obtain quantitative results in quantum chromodynamics (QCD) within strong coupling regime. The JASPER program is programmed in the C++ language and uses the numerical algorithms from the GNU Scientific Library (GSL). The numerical results for dynamical quark mass in complex Euclidean space were obtained. This result will be employed to study the hadron spectrum with the Bethe-Salpeter equation approach.

Decision support system for the proton therapy implementation

The authors propose the method that is intended for automating patient treatment technological process in a proton therapy center and based on a decision support system. The developed information system provides the implementation of the proton therapy protocols. The technological process of the proton therapy is strictly regulated. It includes not only the process of therapy itself (irradiation of the patient), but also the preliminary stages of treatment, as well as the stages following the irradiation process. Proton therapy centers use information systems, such as radiological and hospital information systems (oncology information systems), that provide information support for separate stages. At the moment, there is no system that controls the entire technological process in a proton therapy center. The proposed system ensures that the operator complies with the protocol of the treatment’s stage and supports the entire technological process of the proton therapy. The system sets the schedule of stages, order and possibility of their parallel implementation, determines the conditions for allowing the start of the stage, provides the subsystems with the protocol of the stage and necessary data of protocol to manage the stage by the operator, and also records the results of the completed stage. The system is built on the “client-server” technology. The server has a software part (that implements the concept the server) and a database. For each operator workstation that manages the stage, the client software of the system is additionally installed. The paper describes an approach to creating a decision support system for the personnel of a proton therapy center. Such a system provides the correct implementation and sequence of the proton therapy stages. The system has been included in the project of the Research Proton Therapy Center for Ophthalmic Oncology at Saint Petersburg Nuclear Physics Institute of National Research Center “Kurchatov Institute”. The necessary information is transmitted from the system to the proton therapy center equipment via radiological and hospital information systems using standard protocols. It allows the solution to serve as a part of any automated control system of a radiation therapy center (not only for proton therapy).

The 20-Year Russian-Italian Scientific Collaboration in Industrial Applications of Neutrons and Prospects on High Flux Reactor “PIK” of Russian National Centre “Kurchatov Institute”

The long-term cooperation between the Rogante Engineering Office (REO) and the Petersburg Nuclear Physics Institute (PNPI) of the National Research Centre “Kurchatov Institute” in the field of neutrons industrial applications is discussed, assuming new opportunities associated with the started High Flux Reactor PIK in Gatchina. This large-scale facility is certified as the Centre of Russian and International studies of modern industrial material for advanced technologies, for example IT and microelectronics, pharmaceuticals and biomedicals, catalysts, membranes for hydrogen and solar power, air and cosmic, naval and other sectors.

Development and Construction of Track and Identification Systems for Experiments Aimed at Studying Extreme Properties of Nuclear Matter in Nucleus–Nucleus Collisions

Investigation of properties of nuclear matter at extremely high temperature and/or extremely high baryon densities under laboratory conditions is one of the fundamental lines of research in high-energy physics. Throughout the past decades, such investigations have been performed in collisions of ultrarelativistic heavy ions in several experiments at modern accelerator complexes, including the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL, USA) and the Large Hadron Collider (LHC) at CERN (Switzerland). In the near future, it is also planned to launch investigations of this kind at the FAIR (Facility for Antiproton and Ion Research at Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany) and NICA (Nuclotron-based Ion Collider fAcility at Joint Institute for Nuclear Research (JINR), Dubna, Russia) accelerators. In order to implement such investigations, it is necessary to create sophisticated detector systems that are able to record events featuring high-multiplicity product particles and to measure reliably their properties. The present article gives a brief survey of all detector systems that have already been created and are being developed at Laboratory of Relativistic Nuclear Physics at Petersburg Nuclear Physics Institute (National Research Center Kurchatov Institute) for the PHENIX (BNL, USA), ALICE (CERN, Switzerland), and CBM (GSI, Germany) experiments aimed at studying nuclear matter under extreme conditions.

Молекулярные основы эффекта малых доз радиации

По определению, малые дозы — это минимальные дозы повреждающего агента, в частности радиации, вызывающие регистрируемый биологический эффект. Проблема воздействия малых доз радиации обсуждается в научной литературе в течение десятилетий, но прийти к общему выводу о наличии каких-то особенностей их воздействия, в отличие от таковых острого облучения, не удаётся. Это связано с тем, что эффекты, если они фиксируются, имеют слабое выражение и легко могут быть подвергнуты критике. Другой важный аспект проблемы — то, что биологические эффекты в основном описаны в научной литературе феноменологически, без расшифровки их молекулярных причин. В последние годы появился ряд статей, в которых авторы, изучая действие малых доз ДНК-тропных агентов, показывают, что ключевую роль в этих эффектах играет пострепликативная репарация, в частности её безошибочная ветвь. В лаборатории генетики эукариот Петербургского института ядерной физики имени Б. П. Константинова удалось выделить уникальных мутантов дрожжей с нарушенной ветвью безошибочной пострепликативной репарации. Исследование процессов ликвидации повреждений ДНК при минимальных отклонениях их количества от спонтанного уровня позволило на молекулярном уровне объяснить различия в клеточном ответе на малые дозы от острого облучения.

Development of a Two-Dimensional Thermal-Neutron Detector with an Entrance Window of 600 × 600 mm

A two-dimensional thermal-neutron detector developed for a small-angle diffractometer by the Petersburg Nuclear Physics Institute is described. The detector, with a sensitive area of 600 × 600 mm2, is based on a multiwire proportional chamber. A gas mixture containing 3He is the neutron converter. A new technology for manufacturing electrodes has been developed and used to increase both the gas purity and the lifetime of the detector without refilling its working volume under the experimental conditions. Data acquisition is carried out by the readout system based on the method of cathode-strip data readout to an LC delay line, which is located inside the detector. The detector is operable in a vacuum owing to its design.

Multiple Upsets Induced by Protons and Neutrons in Electronic Devices

90-nm SRAM memory integrated circuits and CCD- and CMOS-matrices have been irradiated by nucleon beams of the synchrocyclotron at the Konstantinov Petersburg Nuclear Physics Institute, National Research Centre “Kurchatov Institute.” Upset cross section data in memory integrated circuits induced by protons with an energy of 1000 MeV and pixels with large value of dark current (spikes) in optoelectronic devices irradiated by protons with an energy of 1000 MeV and neutrons with an energy spectrum similar to the spectrum of atmospheric neutrons have been presented. Most attention has been paid to the study of spike clusters and multiple upsets occurrence. It has been established that most spikes and single event upsets are located in clusters (multiple upsets).

Angular distributions and anisotropy of fission fragments from neutron-induced fission of239Pu,237Np, andnatPb in energy range 1–200 MeV

This work summarizes some results of a series of experiments aimed at the investigation of energy dependence of anisotropy of fission fragments (FFs) in (n,f) reactions for neutron energies from low to intermediate. Angular distributions of FFs from the neutron-induced fission of239Pu,237Np, andnatPb have been measured in the energy range 1–200 MeV at the neutron TOF spectrometer GNEIS based on the spallation neutron source at 1 GeV proton synchrocyclotron of the Petersburg Nuclear Physics Institute (Gatchina, Russia). The anisotropies of FFs deduced from the measured angular distributions are presented. In the neutron energy range above 20 MeV the results have been obtained for the first time in our works. The experimental data for FF anisotropy in237Np(n,f) are compared with calculations based on "adapted" TALYS software.

A Neutron Testing Facility to Study the Radiation Hardness of the Electronic Components at the SC-1000 Synchrocyclotron of National Research Center Kurchatov Institute—Petersburg Nuclear Physics Institute

The article presents a description of the ISNP/GNEIS testing facility with a neutron spectrum that reproduces the spectrum of atmospheric neutron radiation. The facility was developed at the Petersburg Nuclear Physics Institute (PNPI) of the National Research Center Kurchatov Institute in collaboration with the Institute of Space Device Engineering, a branch of JSC (Joint Stock Company) United Rocket and Space Corporation. The spallation neutron source of the facility is based on the 1-GeV SC-1000 proton synchrocyclotron at the PNPI. The internal neutron-production lead target produces 10-ns pulses of neutrons with a repetition rate of 45–50 Hz and an average neutron intensity of 3 × 1014 n/s (in the 4σ solid angle). In the irradiation area located at a distance of 36 m from the neutron source, a high-quality collimated neutron beam with a broad energy spectrum of 1–1000 MeV and a neutron flux of 4 × 105 n/(cm2 s) allows conducting accelerated single-event soft error testing of electronic components. In the course of the irradiation, the neutron energy spectrum and intensity and the spatial profile of the beam are controlled using a fission ionization chamber (beam monitor) and a position-sensitive multiwire proportional counter (beam profile meter). The data acquisition system of the ISNP/GNEIS facility utilizes 250 MS/s 12 bit CAEN waveform digitizers for the processing of signals from the monitor and profile meter by the neutron time-of-flight technique. In the report, parameters of the ISNP/GNEIS testing facility are discussed in comparison with analogous world-class facilities, as well as requirements and recommendations of the standards used in this field.

Precision Measurement of the Proton Charge Radius in Electron Proton Scattering

This report presents a project of an experiment for precision studies of the elastic electron proton scattering in the low momentum transfer region. The project is based on an innovative experimental method which allows for detection of recoil protons in a hydrogen "active target". The goal of the experiment is to measure the $ep$ elastic scattering differential cross section in the $Q^2$ range from 0.001 GeV$^2$ to 0.04 GeV$^2$ with 0.1% relative and 0.2% absolute precision and to determine the proton charge radius with a sub-percent precision. The important advantages of the proposed experiment are low radiative corrections, inherent to the recoil proton method, and absolute measurements of the differential cross sections. The experiment will be performed in the 720 MeV electron beam of the Mainz electron accelerator MAMI. This accelerator can provide an electron beam with optimal for this experiment parameters. The Proposal was approved by the MAMI Program Advisory Committee, and a special Agreement aimed at realization of this experiment was signed between Petersburg Nuclear Physics Institute and Institute of Nuclear Physics of the Mainz University. Also, scientists from the following institutes will participate in this project: GSI Centre for Heavy Ion Research, Germany; Joint Institute for Nuclear Research, Russia; William and Mary College, USA; Mount Allison University, Canada; University of Regina, Canada; Saint Mary's University, Canada. The first measurements should be started in 2020.

Highly efficient ion source for surface and laser ionization

Among the most widely used medical radionuclides there are isotopes of elements with relatively low ionization potential. The simplest type of a mass-separator ion-source in this case is a hot cavity surface ionizer. However, the ionization efficiency of such a type of ionizer for non-alkalis is low (for example, of about 1% for Tl). To increase the surface ionization efficiency, a new material for the surface ion source (monocrystalline tungsten) was used at the mass separator working on-line with the 1-GeV proton synchrocyclotron of Petersburg Nuclear Physics Institute. The ionization efficiency for certain elements with medium ionization potential (Sr, In, Tl) was measured: 45(5)%, 33(8)%, and 21(8)% respectively.

Disagreement between measurements of the neutron lifetime by the ultracold neutron storage method and the beam technique

Recent measurements of the neutron lifetime performed using a gravitational trap of ultracold neutrons (UCNs) (Konstantinov Petersburg Nuclear Physics Institute, Russia) and a magnetic UCN trap (LANL, USA) have confirmed PNPI’s result of 2005. The results of experiments with stored UCNs agree with each other but differ from those of the beam experiment (NIST, USA) by 3.5σ (corresponding to 1% in the decay probability). This disagreement is currently being discussed in the literature as a ‘neutron anomaly’. We analyze possible reasons for that disagreement and test the experimental data for the neutron lifetime and beta-decay asymmetry within the Standard Model. The test is only passed for neutron lifetime values that are obtained using the UCN storage method.

The Electronic System of the Polarized-Neutron Reflectometer for the IR-8 Reactor

The electronics for functional units of the polarized-neutron reflectometer (PNR) is presented. The electronic system connects the reflectometer units to the PNR control computer and provides control of step motors and absolute sensors for moving the experimental equipment, specification and change of the parameters of devices during operation, and acquisition of experimental data in the graphic and digital forms. Devices developed by the Petersburg Nuclear Physics Institute are also included in the electronic system.

Установка для измерения времени жизни нейтрона с большой гравитационной ловушкой при низкой температуре

AbstractCurrently the most accurate measurements of neutron lifetime are being performed at the Petersburg Nuclear Physics Institute with ultracold neutrons (UCNs) stored in a gravitational trap. A modified setup with a large gravitational trap and cooling to 10–15 K is presented. The results of measurements of temperature dependence of UCN losses in collisions with walls, which were coated with a perfluorinated grease (Fomblin UT 18), at 300–77 K, are detailed. The probable heat inflow to the trap is estimated, and the feasibility of cooling to indicated temperatures in experiments with the modified setup is demonstrated.

Angular Distribution and Anisotropy of Fission Fragments in Reactions Induced by Neutrons with Intermediate Energies of 1 to 200 MeV

Experimental data on the angular distributions of 232Th, 233U, 235U, 238U, natPb, and 209Bi fission fragments in reactions induced by neutrons with intermediate energies of up to 200 MeV are presented. Measurements are made using the GNEIS time-of-flight (TOF) spectrometer with the neutron source based on the 1-GeV proton synchrocyclotron of the Petersburg Nuclear Physics Institute. Angular distributions and the anisotropy of fission fragments W(0°)/W(90°) calculated from these distributions are given together with the results of other authors. The disagreement between the results obtained in different works is discussed. The data presented in this work for the anisotropy of natPb and 209Bi fission fragments in reactions induced by neutrons with energies ranging from the fission threshold to 200 MeV are obtained for the first time.