Nuclear Reaction Cross Sections Research Articles

Investigation of neutron-induced reaction cross section calculations for the fusion reactor structural materials using artificial neural networks

Using artificial neural networks for an estimation of the nuclear reaction cross section data is discussed. Approximately rate of the fitting criteria is determined by the calculated experimental data obtained from using Variable Learning Rate Backpropagation (traingdx) algorithm in artificial neural networks. This method has been applied to obtain the cross section for 14–15 MeV neutron-induced (n,α) and (n,p) reactions in the fusion reactor structural materials. In comparison to the reaction cross section calculation by experimental cross sections reported in EXFOR, TALYS 1.9 and EMPIRE 3.2, the proposed method has better prediction ability when the target output has a large variation between the experimental and the calculated data. This study is substantial for the new method validation development of the nuclear model approaches with the increased prediction power of the neutron-induced reactions for fusion reactor systems.

Application of Trojan Horse Method to radioactive ion beams induced reactions

In the last decades, many indirect methods have been developed to measure the cross section of nuclear reactions at the low energies interesting in many astrophysical scenarios. The Trojan Horse Method uses a three body reaction, involving by a strong clusterized nucleus, to infer information about a two body reaction of interest, selecting the events that proceed through the quasi-free reaction mechanism. To reconstruct the reaction kinematic and to identify the useful reaction mechanism, the energy and angle of at least two of the three outgoing particles must be carefully measured. Moreover, enough statistics is required, as the quasi-free events usually represent just a small fraction of the acquired statistic.These requirements hardly match with the typical characteristics of radioactive ion beams: low intensity, large divergence and possible presence of contaminants. For this reason, only recently the Trojan Horse Method has been applied to study reactions induced by radioactive beams. This application gives also the opportunity to measure cross section of neutron induced reactions on radioactive isotopes, even if they have a short lifetime.In the following some results obtained in the study of the reactions 18F(p,α)15O and 18F(n,α)15N will be presented.

Inertial fusion without compression does not work either with or without nanoplasmonics

AbstractA recently published scheme for inertial fusion based on instantaneous heating of an uncompressed fuel is criticized. It is shown that efficient fusion and “time-like” fusion burn propagation cannot be realized due to the low nuclear reaction cross-sections. The suggested use of nanospheres inside the volume of the target to support the fast heating of the fuel is also questioned.

Evaluation of nuclear reaction cross sections for optimization of production of the important non-standard positron emitting radionuclide 89Zr using proton and deuteron induced reactions on 89Y target

89Zr (T1/2 = 3.27 d) is an important β+-emitting radionuclide of zirconium used in immuno PET. The excitation functions of the 89Y(d,2n)89Zr and 89Y(p,n)89Zr reactions were analyzed to deduce the optimum conditions for the high purity production of 89Zr. The nuclear model codes ALICE-IPPE, EMPIRE 3.2 and TALYS 1.9 were used to check the consistency and reliability of the experimental data. A polynomial fit to the chosen data for each reaction gave the excitation function, which was then used for the integral yield calculation of the product. The amount of the major radioactive impurity 88Zr was precisely analyzed for both the proton and the deuteron induced reactions on the 89Y target.

The Pion Single-Event Effect Resonance and its Impact in an Accelerator Environment

The pion resonance in the nuclear reaction cross section is seen to have a direct impact on the single-event effect (SEE) cross section of modern electronic devices. This was experimentally observed for single-event upsets and single-event latchup. Rectangular parallelepiped (RPP) models built to fit proton data confirm the existence of the pion SEE cross-section resonance. The impact on current radiation hardness assurance (RHA) soft error rate (SER) predictions is, however, minimal for the accelerator environment since this is dominated by high neutron fluxes. The resonance is not seen to have a major impact on the high-energy hadron equivalence approximation established for testing in mixed-field facilities.

$${T}$$-Invariance Conditions for Differential Cross Sections for Binary Nuclear Reactions Involving Spin-Oriented Particles and Nuclei

By employing the $$T$$ -invariance condition for the amplitudes describing arbitrary binary nuclear reactions that involve spin-oriented particles and the respective time-reversed reactions, a relation between the differential cross sections for these reactions is obtained for the first time. These cross sections are determined with the aid of sets of potentials simulating the interaction between particles of the initial and final reaction channels and not including any of spin–orbit interactions. The resulting relation covers the case corresponding to the implementation of the previously known detailed-balance principle. This relation is used to derive equalities between the components appearing in the cross sections under analysis via a unified mechanism and possessing identical $$P$$ and $$T$$ parities. These equalities make it possible to prove the existence of a number of components in the cross section that vanish upon taking into account $$T$$ invariance, and this opens new possibilities in studying $$T$$ -noninvariant interactions in nuclear reactions.

Analytic Continuation of Scattering Data, Asymptotic Normalization Coefficients, and Astrophysics

The formalism of asymptotic normalization coefficients and methods for determining them from experimental nuclear data are discussed. A new method is proposed that uses the continuation of the modulus squared of a partial-wave amplitude. It is shown that the recently proposed $$\Delta$$ method for the continuation of elastic scattering data is not strictly correct. It is argued that, unlike asymptotic normalization coefficients, the values of spectroscopic factors cannot be unambiguously determined from experimental data on nuclear reactions. The Trojan horse method is discussed, which allows one to determine cross sections of binary astrophysical nuclear reactions from the data of reactions with three particles in the final state.

High precision half-life measurement of ^{95}hbox {Ru}, ^{95}hbox {Tc} and ^{95m}hbox {Tc} with gamma -spectroscopy

The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the ^{92}hbox {Mo}(alpha ,n)^{95}hbox {Ru} reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of ^{95}hbox {Ru}, derived about half a century ago, is overestimated. Therefore, the half-lives of ^{95}hbox {Ru} and its daughter isotope ^{95}hbox {Tc} and ^{95m}hbox {Tc} have been measured with high precision using gamma -spectroscopy. The results are hbox {t}_{1/2} =1.6033 pm 0.0044 h for ^{95}hbox {Ru}, hbox {t}_{1/2} =19.258 pm 0.026 h for ^{95}hbox {Tc} and hbox {t}_{1/2} =61.96 pm 0.24 d for ^{95m}hbox {Tc}. The precision of the half-life values has been increased, consequently the recently measured ^{92}hbox {Mo}(alpha ,n)^{95}hbox {Ru} activation cross section will become more precise.

The periodic table and the physics that drives it.

Mendeleev's introduction of the periodic table of elements is one of the most important milestones in the history of chemistry, as it brought order into the known chemical and physical behaviour of the elements. The periodic table can be seen as parallel to the Standard Model in particle physics, in which the elementary particles known today can be ordered according to their intrinsic properties. The underlying fundamental theory to describe the interactions between particles comes from quantum theory or, more specifically, from quantum field theory and its inherent symmetries. In the periodic table, the elements are placed into a certain period and group based on electronic configurations that originate from the Pauli and Aufbau principles for the electrons surrounding a positively charged nucleus. This order enables us to approximately predict the chemical and physical properties of elements. Apparent anomalies can arise from relativistic effects, partial-screening phenomena (of type lanthanide contraction) and the compact size of the first shell of every l-value. Further, ambiguities in electron configurations and the breakdown of assigning a dominant configuration, owing to configuration mixing and dense spectra for the heaviest elements in the periodic table. For the short-lived transactinides, the nuclear stability becomes an important factor in chemical studies. Nuclear stability, decay rates, spectra and reaction cross sections are also important for predicting the astrophysical origin of the elements, including the production of the heavy elements beyond iron in supernova explosions or neutron-star mergers. In this Perspective, we critically analyse the periodic table of elements and the current status of theoretical predictions and origins for the heaviest elements, which combine both quantum chemistry and physics.

Radiation damage in particle accelerator complex for heavy ion inertial fusion

We investigated radiation damages induced by irradiating ions in a particle accelerator for a heavy-ion inertial fusion (HIF) system, because the radio-activation is an unavoidable issue to realize the future HIF power plant. In this study, we estimated the radio-activation at each part of the HIF accelerator. An evaluation using collisions due to Coulomb barrier gives the safer estimation in the radio-activation of the vacuum vessel wall. The estimation results of total cross sections of nuclear reactions between an incident ion and wall elements showed the potential radio-activation parts in the HIF accelerator. We indicated that schematic layouts of two types of HIF accelerators with the nuclear reaction cross section, and the activated area for the HIF accelerator was evaluated.

Cross section of 15N-2D nuclear reactions from 3.3 to 7.0 MeV for simultaneous hydrogen and deuterium quantitation in surface layers with 15N ion beams

The cross section for the combined 2D(15N,p)16N and 2D(15N,nγ)16O nuclear reactions of deuterium (2D) with incident 15N ions is evaluated and found to increase by two orders of magnitude between 3.3 and 7.0 MeV. Detecting the γ-rays at 6.1 and 7.1 MeV from these reactions allows quantifying the depth-integrated 2D content in materials in parallel with nanometer-resolved quantitative hydrogen (1H) depth profiling in surface layers through resonant 1H(15N,αγ)12C nuclear reaction analysis (NRA) using 15N ion beams. The information depth and sensitivity of 15N-2D NRA is estimated through energy loss simulations of the 15N projectiles in the analyzed material. Good agreement of the integral 2D quantitation through 2D(15N,p)16N and 2D(15N,nγ)16O NRA with 2D depth profiles obtained independently via 2D(3He,p)4He NRA is demonstrated at the example of 2D plasma-exposed tungsten samples. The simultaneous quantitation of 2D and depth-resolved 1H profiling with a single 15N ion beam promises application potential to investigate hydrogen-isotope exchange and diffusion processes in surface and thin buried layers.

The empirical cross section behavior of (d, 3n) reaction for 20±1.5 MeV energy

Many nuclear reaction cross-section formalism has been developed for particle induced reaction up to date. In this study, a new empirical (d, 3n) cross section formulae systematic have been developed at 45≤A≤112 mass range for 20 ± 1.5 MeV incident deuterium energy. Also, (d, 3n) systematic have been grouped according to Even-N and Odd-Z numbers around 45≤A≤209 mass range. The Levkovskii asymmetry (N-Z/A) parameter have been used to improve empirical (d, 3n) cross section formula systemic. By using obtained new (d, 3n) empirical formulae systematics, theoretical (d, 3n) cross section calculations are made and the results have been found good agreement with the EXFOR data.

Investigation of the deuteron induced nuclear reaction cross sections on lutetium up to 50\xa0MeV: review of production routes for 177Lu, 175Hf and 172Hf via charged particle activation

In a systematic study of light charged particle induced nuclear reactions we investigated the excitation functions of deuteron induced nuclear reactions on natural lutetium targets. Experimental excitation functions up to 50 MeV on high purity natLu were determined using the standard stacked foil activation technique. High resolution off-line gamma-ray spectrometry was applied to assess the activity of each foil. From the measured activity direct and/or cumulative elemental cross-section data for production of 171,172,173,175Hf, 171,172,173,174g,176m,177m,177gLu and 169Yb radioisotopes were determined. The experimental data were compared to results of the TALYS theoretical code taken from the TENDL databases and results of our calculations using the ALICE-IPPE-D and the EMPIRE-D codes. No earlier experimental data were found in the literature. Thick target yields for the investigated radionuclides were calculated from the measured excitation functions.

Gamma-ray emission in alpha-particle reactions with C, Mg, Si, Fe

Cross sections for the strongest γ-ray emission lines produced in α-particle reactions with C, Mg, Si, Fe have been measured in the range E α = 50-90 MeV at the center for protontherapy at the Helmholtz-Zentrum Berlin. Data for more than 60 different γ-ray lines were determined, with particular efforts for lines that are in cross section compilations/evaluations with astrophysical purpose, and where data exist at lower projectile energies. The data are compared with predictions of a modern nuclear reaction code and cross-section curves of the latest evaluation for gamma-ray line emission in accelerated-particle interactions in solar flares.

Perspectives on nuclear data for advanced reactor design and analysis

Nuclear reaction cross section and other neutron physics data are basic inputs to reactor design and analysis. The physical constants such as reaction cross section and other physical constants are usually generated in labs with neutrons as probes, are then coded and subject to detailed evaluation and qualification and finally are made ready for use for potential reactor applications. The nuclear data measurement requires cutting edge technologies from generation of mono-energetic source of neutrons to developing pure targets and covering the entire range of neutron energies and reaction channels. The evaluated data which are created from a best fit of several experiments are then processed to a reactor-specific dataset which again is a multi-parametric and required different treatment in different energy regimes and is also for different target isotopes. The life cycle of these physical constants from lab to the user is very large, sometimes spans over a few decades. This field of nuclear data physics, which entails multi-physics covering the entire gamut from experiments to processing, is an exciting branch of reactor design. This paper attempts to give an overview of the importance of these cross-section data for design studies, safety and operation of reactors. Emphasis is mainly in the condensed nuclear datasets used of design simulations. Advanced reactor designs use newer materials, are optimized for better fuel utilization and are required to model more complex phenomenon. All these require that the uncertainties in the basic nuclear data be minimized. The deviations in core parameters due to the variations in basic nuclear cross sections are estimated as sensitivity or uncertainty coefficient, which are then accounted for in the design margins. This paper will cover the various aspects of the nuclear data, i.e., experiments to reactor-specific data, its use in reactors, the influence on operational parameters and sensitivity studies.

Experimental investigation and theoretical evaluation of proton induced nuclear reactions on nickel

The cross-sections for proton-induced nuclear reactions on natural nickel were experimentally measured for the natNi(p,x)60,61,64Cu, natNi(p,x)55,57,58Co and natNi(p,x)57Ni reactions from their respective thresholds up to 17 MeV proton energy. The stacked-foil technique in combination with HPGe γ-ray spectroscopy was used. Three codes were used in the theoretical calculations namely ALICE-IPPE, EMPIRE-3.2.2 and TENDL-2017. Comparison of the present results with the earlier reported experimental data and with the code results were carried out.

Underground Nuclear Astrophysics: pushing direct measurements toward the Gamow window

The aim of experimental nuclear astrophysics is to provide information on the nuclear processes involved in astrophysical scenarios at the relevant energy range. However, the measurement of the cross section of nuclear reactions at low energies present formidable difficulties due to the very low reaction rates often overwhelmed by the background. Several approaches have been proposed and exploited to overcome such severe obstacles: in such frame, the idea to install a low energy - high intensity ion accelerator deep underground, to gain high luminosity while reducing the cosmic ray background, brought more than 25 years ago, to the pilot LUNA experiment. LUNA stands for Laboratory for Underground Nuclear Astrophysics: in the cave under the Gran Sasso mountain (in Italy) first a 50 kV and then a 400 kV single-ended accelerator for protons and alphas were deployed and produced plenty of data mainly on reactions of the H-burning phase in stars. Recently, similar facilities have been installed and/or proposed in other underground laboratories in US and China. LUNA as well is going to make a big step forward, with a new machine in the MV range which will be able to provide intense beams of protons, alphas and carbon ions. The rationale of underground nuclear astrophysics will be presented together with the last updates on the ongoing research programs.

Synergy of Nuclear Data and Nuclear Theory Online

The paper describes the NRV web knowledge base on low-energy nuclear physics developed in the Joint Institute for Nuclear Research. The NRV knowledge base working through the Internet integrates a large amount of digitized experimental data on the properties of nuclei and nuclear reaction cross sections with a wide range of computational programs for modeling of nuclear properties and nuclear dynamics. Today, the NRV becomes a powerful instrument for nuclear physics research as well as for educational applications. Advantages of the functioning scheme of the knowledge base provide the synergy of coexistence of the experimental data and computational codes within one platform.

Development of neutron activation system on EAST.

A neutron activation system (NAS) has been developed on the Experimental Advanced Superconducting Tokamak (EAST) for the investigation of time-integrated neutron yield. It is a robust neutron diagnostic with high precision and a wide dynamic range. Some high purity materials with a proper nuclear reaction energy threshold and cross section are tested as neutron detectors in the NAS, and they are delivered to the tokamak device by a pneumatic transfer system. The length of the pneumatic pipeline is about 50 m, and the transfer time ranges from 10 s to 20 s. The decay gamma rays of the activated samples are measured with a high-purity germanium spectrometer, and its detection efficiencies are 6.9% at 336 keV and 1.7% at 1779 keV, respectively. Indium and silicon samples with a reaction threshold of 0.3 MeV and 4.0 MeV, respectively, were successfully implemented in the diagnosis of DD and DT neutron yield in the EAST. The neutron flux of the NAS was compared with the count of the fission chamber in the EAST neutral beam injection experiment, and the DD neutron yield evaluated by the NAS ranges from 1.9 × 1012 n/shot to 5.9 × 1014 n/shot during recent experimental campaign.

Study of Astrophysical s-Process Neutron Capture Reactions at the High-Intensity SARAF-LiLiT Neutron Source

We report on recent experiments at the Soreq Applied Research Accelerator Facility Liquid-Lithium Target (SARAF-LiLiT) laboratory dedicated to the study of s-process neutron capture reactions. The kW-power proton beam at 1.92 MeV (1-2 mA) from SARAF Phase I yields high-intensity 30 keV quasi-Maxwellian neutrons (3-5×1010 n/s). The high neutron intensity enables Maxwellian averaged cross sections (MACS) measurements of low-abundance or radioactive targets. Neutron capture reactions on the important s-process branching points 147Pm and 171Tm were investigated by activation in the LiLiT neutron beam and γ-measurements of their decay products. MACS values at 30 keV extracted from the experimental spectrum-averaged cross sections are obtained and will be discussed. The Kr region, at the border between the so-called weak and strong s-process was also investigated. Atom Trap Trace Analysis (ATTA) was used for the first time for the measurement of a nuclear reaction cross section. After activation in the quasi-Maxwellian neutron flux at SARAF-LiLiT, isotopic ratios were determined for 81Kr(230 ky)/80Kr and 85gKr(10.8 y)/84Kr. The latter ratio was confirmed both by low-level β counting and γ spectrometry. The shorter-lived capture products 79,85m,87Kr were detected by γ -spectrometry and the corresponding neutron-capture MACS of the respective target nuclei 78,84,86Kr were determined. The MACS of the 80Kr(n, γ)81Kr and 84Kr(n, γ)85gKr reactions are still under study. The partial MACS leading to 85mKr(4.5 h) measured in this experiment has interesting implications since this state decays preferentially by γ decay (79%) to 85Rb on a faster time scale than does 85gKr and behaves thus as an s-process branching point.