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The nature of dark matter is one of the issues most actively discussed in both cosmology and particle physics. The progress in observational cosmology and determination of many parameters of the standard cosmological model (SCM) is insufficient to shed light on the nature of dark energy, the origin of the particle-antiparticle asymmetry in the Universe, the causes of the inflationary period, the cosmological lithium problem, etc. This paper attempted to gain a new insight into the nature of the dark matter through the idea of G. Gamow (1946) who assumed that a primordial hot universe consisted only of neutrons. The assumption is argued that the dark matter consists of baryons (neutrons) similar to ordinary matter (neutrons and protons). Experiments are proposed to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

The study of the 3H(1H, γ)4He reaction is of relevance for both nuclear physics and nuclear astrophysics. In nuclear astrophysics, more accurate data should be obtained on the rate of primordial nucleosynthesis reactions that lead to the production of 4He. In nuclear physics, there are theoretical models in which the behavior of the cross section and the S-factor of this reaction in the energy range of the order of tens of keV are in poor agreement with experiment. Thereby, more accurate experimental study of S-factor behavior should be performed in the astrophysical energy range. The experimentally obtained values of the yields for various energies of 1H+ ions were used to describe the behavior of the 3H(1H, γ)4He reaction S-factor depending on the energy. As a result, the accuracy of determination of the S-factor of the 3H(1H, γ)4He reaction has been improved several times. [ABSTRACT FROM AUTHOR]

The study of thermonuclear reactions such as D(d, p)3H, D(d, n)3He, T(d, n)3He, 3He(d, p)4He, and D(3He, p)4He is of great interest in the field of astrophysics, as it affects the primordial nucleosynthesis, as well as issues of stellar dynamics. These reactions are also of interest in thermonuclear power engineering, in connection with the increased interest in the possibility of practical application of thermonuclear fusion. In this work, the analysis of the results obtained in the course of studying the reaction D(3He, p)4He was carried out. The results were obtained by us in previous works on deuterated metal targets ZrD and TiD with Miller indices [111] and [100]. There is a need to more precise study of the effects accompanying thermonuclear reactions at low astrophysical energies. The purpose of this work is to study the behavior of the screening potential U e and the reaction enhancement factor f (E) , depending on the crystal structure of targets and the interaction energy. The studies were carried out on a Hall accelerator (Tomsk, TPU) in the energy range E ( 3 He) = 1 6 − 3 4 keV in lab reference frame with a step of 2 keV. Experiments have shown that in reactions using metal deuterated targets a similar effect as in reactions using gas targets was observed. Specifically, an electron screening effect was observed, which leads to an increase in the reaction cross-section with decreasing energy, and in case of metal target this effect becomes stronger. [ABSTRACT FROM AUTHOR]

The T(1H, γ)4He reaction has been studied for the first time in the energy range Elab = 12–34 keV in the laboratory coordinate system (E = 7.8–20.1 keV in the center-of-mass system). The study of this reaction is of interest because it is involved in the primary nucleosynthesis of 4He and is important for the theory of few-nucleon systems. The reported experiment improves the accuracy of the experimental determination of the S-factor of the T(1H, γ)4He reaction by several times. The theoretical calculations of the S-factor of the T(1H, γ)4He reaction still differ from the experimental values by a factor of about 2. [ABSTRACT FROM AUTHOR]

Acceleration of ions to multi-MeV energies is investigated in various plasma devices to better understand processes in astrophysical plasmas and to develop efficient accelerators for a variety of applications. This paper reports the production of proton, deuteron, and electron beams in a z-pinch—a cylindrically symmetric plasma column that is compressed by its own magnetic field. For this work, the GIT-12 pulsed-power generator was used to drive a novel configuration of z-pinch that dramatically enhanced ion acceleration associated with disruption of the current by instabilities in the compressed plasma. During the disruption of 3 MA current, hydrogen ions were accelerated up to at least 50 MeV, which is almost a hundred-times the ion energy provided by the generator driving voltage of 0.6 MV. Under optimal conditions, the total numbers of hydrogen ions with energies above 20 and 50 MeV were 4 × 1013 and 1011, respectively. Accelerated deuterons produced one 20 ns (full width at half maximum) pulse of fast neutrons via D(d, n)3He and other nuclear reactions. A maximum neutron output of (1.0 ± 0.2) × 1012 neutrons/sr was observed downstream, i.e., in the anode to cathode direction. In this direction, the maximum neutron energy reached 58 ± 7 MeV. Both ion and neutron beams in our experiment reached an end-point energy of about 60 MeV, which is the highest value observed in pulsed-power devices. A localized peak voltage of ≳60 MV was driven by the inductive energy that was stored around the plasma column and that was extracted during a sub-nanosecond current drop. Considering the natural occurrence of current-carrying columns in laboratory and space plasmas, the current interruption observed in z-pinches could represent a more general physical process that contributes to the efficient conversion of magnetic energy into the energy of particle beams in various plasmas. [ABSTRACT FROM AUTHOR]

Deuterium gas-puff z-pinches are very efficient laboratory sources of neutron pulses. Using a novel hybrid gas-puff load on the GIT-12 generator, a significant increase in the neutron yields up to 5.6 × 10 12 is reached. At the same time, a very broad neutron energy spectrum up to energies on the order of tens of MeV is observed. In these experiments, the neutrons are produced not only by the D(d,n)3He (DD) nuclear reaction but also by reactions of multi-MeV deuterons with the experimental hardware. The angular distribution of the neutron fluence and dependence of the fluence on the distance from the z-pinch are measured using neutron activation diagnostics. By this method, a number of produced non-DD neutrons and anisotropy of DD neutron emission are evaluated. [ABSTRACT FROM AUTHOR]

The study of fusion reactions D (d , p) 3 H , D (d , n) 3 He , T (d , n) 3 He , 3 He (d , p) 4 He , and D (3 He , p) 4 He at astrophysical energies is of interest for both basic and applied physics. These studied provide information on electron screening of nuclear reactions that provide important information on the role of electrons in reactions induced by deuterons, tritons, and nuclei of helium isotopes that proceed in reactors. The D (3 He , p) 4 He reaction was investigated at the pulsed plasma Hall accelerator (Tomsk) in the 3 He + ion energy range E He = 16 ÷ 34 keV (laboratory reference frame) with a step of 2 keV. The goal of this work was to determine experimentally the enhancement factor of the D (3 He , p) 4 He reaction and the electron screening potential U e using a TiD targets with Miller indices [111] and [100]. A strong impact of the target crystal structure on reaction enhancement factor was discovered. We believe that solid-state effects make the largest contribution to the behavior of the enhancement factor D (3 He, p) 4 He of the reaction as a function of energy. One of these effects is the particle channeling in crystal structures. An unexpected increase of the enhancement factors for the D (3 He, p) 4 He reaction in the energy range 16 ÷ 22 keV probably indicates the emergence of some new mechanism that increases the yield of the reaction with lowering energy. [ABSTRACT FROM AUTHOR]

The D(3He, p)4He reaction is first investigated in a solid target of deuterated zirconium (ZrD) in the 3He+ ion energy range EHe = 18-30 (E = 7.2−12.0keV keV in the center-of-mass system) with a step of 2 keV. The electron screening potential Ue = (617.8 ± 154.7) eV and the D(3He, p)4He reaction enhancement factors are experimentally determined in the given energy range. The measured electron screening potential is six times higher than in gaseous targets. This can be due to the ZrD lattice effects, which have not been studied either theoretically or experimentally so far. The D(3He, p)4He reaction has been investigated at the pulsed plasma Hall accelerator (Tomsk). [ABSTRACT FROM AUTHOR]

Data on the growth rate of an adsorbed film on a target are obtained using a quartz resonator upon operation with an accelerator with closed electron drift. The target is shown to be purified at 55°C and a flux of accelerated (12 keV) deuterium particles (about 5 × 1012 cm-2) and the dynamic equilibrium of sorption and desorption processes is established. The yield of neutrons increases during the d(d,n)3He nuclear reaction due to purification of the target. [ABSTRACT FROM AUTHOR]

A set of neutron diagnostics including scintillation time-of-flight detectors, bubble detectors, and several kinds of threshold nuclear activation samples is used to obtain information about the yield and spectrum of the neutrons produced by a deuterium gas-puff z-pinch. The experiments are performed at a current of about 3 MA on the GIT-12 generator at the Institute of High Current Electronics of the Siberian Branch of Russian Academy of Sciences in Tomsk. The average neutron yield in the experiments in 2016 was 2.3 × 1012 neutrons per single shot. Using the data obtained with the help of neutron activation diagnostics, the time-of-flight detectors have been absolutely calibrated and the broad energy spectrum of the produced neutrons was evaluated. By the calculations presented in this paper, due to the multi-MeV energies of deuterons generated in the pinch, up to 15% of the total neutron yield could be produced by nuclear reactions of deuterons with a stainless steel vacuum chamber and aluminum [ABSTRACT FROM PUBLISHER]

An experiment in direct registration of neutron nuclei () using a multineutron detector has been conducted for the first time. The results indicate the presence of hexaneutron and/or octaneutron emission in decay of U nuclei. The multineutron detector consisted of 20 3He-filled counters placed in a polyethylene moderator. Samples (emitters) of uranium trioxide (UO3) were used as sources of neutron nuclei. The experiment was conducted for a period of 112.66 days. Thus, the ratios of probabilities of hexaneutron and/or octaneutron emission by the U nuclei to the probabilities of -decay have been determined as upper bounds at a 90% confidence level: and . [ABSTRACT FROM AUTHOR]

A novel configuration of a deuterium z-pinch has been used to generate a nanosecond pulse of fast ions and neutrons. At a 3 MA current, the peak neutron yield of (3.6±0.5)×1012 was emitted within 20 ns implying the production rate of 1020 neutrons/s. High neutron yields resulted from the magnetization of MeV deuterons inside plasmas. Whereas deuterons were trapped in the radial direction, a lot of fast ions escaped the z-pinch along the z-axis. A large number of >25MeV ions were emitted into a 250 mrad cone. The cut-off energy of broad energy spectra of hydrogen ions approached 40 MeV. The total number of >1MeV and >25MeV deuterons were 1016 and 1013, respectively. Utilizing these ions offers a real possibility of various applications, including the increase of neutron yields or the production of short-lived isotopes in samples placed in ion paths. On the basis of our experiments with various samples, we concluded that a single shot would have been sufficient to obtain GBq positron activity of 13N isotopes via the 12C(d,n)13N reaction. Furthermore, the first z-pinch generated neutron radiograph produced by ≈ 20 ns pulses is presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents results of the application Monte Carlo method to analyze data from the interaction of deuteron beams with metallic targets saturated with deuterium. The SRIM software was used to generate energy spectrum of ions passing the target. These spectra were used to calculate the neutron yields from dd reactions in energy range 7-12 keV of incident deuteron beams. The calculated outputs were compared with the experimental data for the determination of the electron screening potential for dd reactions. The calculations were performed using two different values of the beam energy spread (FWHM) equal 1% and 16%. It was shown that plasma beams with a relatively high spread (16%) were almost as good a tool as the traditional accelerator with mono-energy beam related to the study of the reaction within an ultra-low energy region. [ABSTRACT FROM AUTHOR]

The results of the measurements of the astrophysical S -factor and cross-sections of the reaction dd → ^3He+ n in the deuteron energy collision range of 2.3-6.2keV are presented. The experiment was carried out at the high-current deuteron beam of the Hall pulsed accelerator (FSSI “Nuclear Physics Institute”, Tomsk). Deuterated polyethylene (CD2) targets and frozen heavy water (D2O) were used. Neutrons were detected by eight plastic scintillation counters ( 375×100×100 mm^3) located around the target. The results obtained in the present work substantially differ from the results of the experiments conducted with the use of deuterium saturated metal targets (TiD, TaD, ZrD, PtD). Within statistical errors of measurements there is no discrepancy between the present results and the results of the experiments performed with the heavy-water targets and filled with gaseous-deuterium targets. [ABSTRACT FROM AUTHOR]

Results are presented from experimental studies of the neutron emission generated in the collision of deuterium plasma flows produced in discharges in crossed E×H fields and propagating in opposite directions in a neutral gas across an external magnetic field. It is shown that the interaction of oppositely propagating deuterium plasma flows gives rise to the generation of soft X-ray emission and neutron emission from the dd reaction (dd→3He + n) and is accompanied by an almost complete depolarization of the flows and rapid variations in the magnetic field (at a rate of ∼1011 G/s). The measurements were performed at energies and velocities of the flows of up to 600 J and 3.5×107 cm/s, respectively. The plasma density in each flow was ∼1015cm–3. The upper estimates for the astrophysical S factor and the effective cross sections of the dd reaction obtained from our measurements are compared to theoretical calculations and to the results of experiments performed in the MIG high-current accelerator (Institute of High-Current Electronics, Russian Academy of Sciences, Tomsk). © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The pd reaction (pd →3 He + γ (5.5 MeV)) is studied in the astrophysical energy collision range of protons with deuterons using the hydrogen liner in the inverse Z-pinch configuration at the pulsed power generator MIG (HCEI, Tomsk). Fundamental characteristics of this and other light-nucleus reactions at ultralow energies are important for problems of basic physics and astrophysics. The knowledge of the energy distribution of the nuclei participating in these reactions is important due to their exponential type of dependence on the collision energy. Two experimental techniques were designed and tested for recovering the energy distribution of liner protons incident on the CD2 target by using optical detectors and ion collectors. It is shown that the combined use of these two techniques could provide relevant information on the energy distribution of the accelerated protons in the liner. The estimates of the upper limits for the astrophysical S factor and effective cross section of the pd reaction in the proton–deuteron collision energy range of 2.7–16.7 keV are obtained: Spd(Epd = 10.2 keV) ≤ 2.5 × 10–7 MeV b; σpd(2.7 ≤ Epd ≤ 16.7 keV) ≤ 4 × 10–33 cm2.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The spectrum of γ rays from the neutron-induced fission of 235U nuclei has been studied in a range of 10–90 MeV. The experiment has been carried out in the horizontal experimental channel of a nuclear reactor. The energy spectrum was measured using a single-crystal NaI(T1) spectrometer. The data on the energy dependence of the yield of γ rays have been obtained in a range of 12–38 MeV. The upper limit on the probability of the emission of γ rays has been determined for a range of 38–90 MeV. It has been shown that the experimental data are inconsistent with available models attributing the yield of γ rays in this energy range to the coherent bremsstrahlung of fission fragments in the Coulomb field. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Results of an experiment on the search for the emission of π0 mesons in neutron-induced fission of 235U nuclei based on the detection in coincidence of two γ-quanta from the π0-meson decay performed with the nuclear reactor developed at the Scientific-Research Nuclear Physics Institute at Tomsk Polytechnic University are described. The experimental setup comprised two Čerenkov spectrometers of total absorption for the detection and measurement of γ-quantum energy placed in two coaxial horizontal channels of the nuclear reactor. Water filters placed in the channels were used to protect the detectors from β-, γ-, and neutron fluxes. To reject the cosmic radiation, scintillation counters of large area, operating in anticoincidence mode, were placed above each spectrometer. The experimentally measured limitation on the probability of neutral pion emission in neutron-induced fission of nuclei was established ≤4.1·10–11 with a 90% confidence level. The energy spectrum of γ-quanta from the active reactor zone was measured in the range 32–65 MeV. The parameters of the spectrum deviated from the results of theoretical calculations and from the experiment performed with the nuclear pulse reactor developed at the Joint Institute for Nuclear Research (Dubna). [ABSTRACT FROM AUTHOR]

A method and results of measurements are presented of the ion energy distribution in a deuterium liner accelerated in the inverse Z-pinch, in which the plasma is accelerated electrodynamically from the liner axis. Knowledge of the deuteron energy distribution is of primary importance for the correct interpretation of the experimental results from the study of the dd-reaction in the range of infralow energies with the use of a liner plasma. Experiments were carried out in a high-current pulsed accelerator (I = 950 kA, τ = 80 ns) at the Institute of High-Current Electronics of the Siberian Division of the Russian Academy of Sciences (Tomsk, Russia). In the initial state, the liner is a supersonic hollow deuterium jet 32 mm in diameter and 20 mm in length. The liner parameters were measured with the help of optical detectors of H[sub α] and H[sub β] deuterium lines and magnetic probes arranged in a radial direction (along the direction the liner expansion). In addition, scintillation spectrometers and BF[sub 3] counters were used to measure the intensity of the neutron flux produced in the d + d → ³He + n reaction. The results obtained by simultaneously analyzing the data from magnetic probes, optical detectors, and neutron detectors point to the possibility of using a rather simple method for measuring the parameters of the liner accelerated up to energies of 3-6 keV. [ABSTRACT FROM AUTHOR]

It is found experimentally that the interaction of plasma flows propagating in opposite directions across a magnetic field is accompanied by periodic local bursts of intense optical and soft X-ray emission. It is shown that periodic variations in the emission intensity from the interaction region are related to the excitation of steady-state self-oscillations in the plasma. By varying the frequency and amplitude of these oscillations, it is possible to satisfy the resonance conditions at certain characteristic plasma frequencies. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Results are presented from numerical calculations of the maximum energy of accelerated deuterons as a function of the magnetic field for two models of the formation of the accelerating field in the region where two magnetosonic shock waves collide. The numerical results are compared with the similar experimental dependence. © 2000 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A study is made of the effect of the initial magnetic field magnitude on the energy of deuterium ions accelerated in the collision of two magnetosonic shock waves propagating in a deuterium plasma quasi-perpendicularly to the magnetic field. Experiments were carried out at a constant plasma density of =2.5×10[sup 13]cm[sup –3]. It is found that, as the external magnetic field decreases from 1.4 to 0.7 T and, accordingly, the magnetic Mach number increases from 1.02 to 2.3, the energy of accelerated ions increases from 3.2 to 7.5 MeV. The maximum number of accelerated ions attains 10[sup 5]–10[sup 6] particles per shot. © 2000 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A nuclear-reactor experiment on the search for the emission of neutral pions from the neutron-induced fission of 235U nuclei has been carried out. To this end, an experimental setup for searching for the emission of π0 mesons with high sensitivity to this process has been designed and produced. This setup consisted of two Cherenkov total-absorption spectrometers for the detection and measurements of the energy of two gamma-ray photons from π0-meson decay. The spectrometers were placed at the exits of two coaxial horizontal experimental channels. To protect the detectors from low-energy β and γ rays and neutron fluxes, 3.5-m-long water filters were situated in the channels. To reject the cosmic background, large-area scintillation counters operating in the anticoincidence mode were placed over each spectrometer. The energy and time resolution of the spectrometers, as well as the efficiency of detecting charged particles by scintillation counters, were tested on the secondary electron beam of the Tomsk electron synchrotron Sirius. Runs of measurements of the effect on the operating reactor (duration of 805 h) were alternated with runs of measurements of background on the stopped reactor (duration of 403 h). Statistical processing of the experimental results yields an upper limit of ≤5.3×10–12 with a 90% confidence level for the probability of the emission of neutral pions from the neutron-induced fission of 235U nuclei. This result and results of other works carried out with sources of spontaneously fissioning 252Cf nuclei show that the probabilities of the emission of π0 mesons from spontaneous fission and fission induced by fission-spectrum neutrons are equal to each other. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Presents a correction to an article previously published in a 2004 issue of "JETP Letters."