Spallation Reactions Research Articles

Comparison of spallation reaction models based on multiple-criteria decision analysis

The paper presents the results of a comparative evaluation of the predictive ability of seventeen spallation reaction models (CEM02, CEM03, Phits/jam, Cascade/ASF, Phits/Bertini, Bertini/Dresner, Cascade-4, INCL4/Abla, INCL4/smm, geant4/binary, Isabela/smm, geant4/Bertini, Isabela/Abla, INCL4/Gemini, CASCADeX-1.2, Isabel/Gemini, Phits/jqmd) for the interaction reactions of high-energy protons with natPb nuclei using the most popular methods of multiple-criteria decision analysis (MAVT/MAUT, AHP, TOPSIS, PROMETHEE). Multiple-criteria decision analysis methods are used extensively to support decision-making in various fields of knowledge, including nuclear physics and engineering, when aggregating conflicting criteria with due account for the expert and decision-maker opinions. Four factors of computational and experimental agreement (R, D, F, H), most commonly used in this field of knowledge, have been employed as the criteria, which, having been aggregated as part of applying respective multiple-criteria decision analysis methods, make it possible to estimate the integral measure of the computational model effectiveness and to rank the models, using this as the basis, depending on the degree of their predictive ability. It has been demonstrated that the ranking results obtained using different multiple-criteria decision analysis methods show a good agreement. Using a stochastic approach to the generation of weights, the models were ranked in conditions with the absence of data on the significance of individual agreement factors. Recommendations are presented for using the multiple-criteria decision analysis methods to address tasks involved in the preparation of nuclear data in conditions of a multiple-factor evaluation of discrepancies between calculations and experiment.

Unified description of the fission probability for highly excited nuclei

ABSTRACT We present a new model to describe the fission probability of the high-energy fission model, as deduced from the intra-nuclear cascade calculation with the Intra-Nuclear Cascade model of Liége (INCL) version 4.6 and Prokofiev’s phenomenological systematics of the proton-induced fission cross-sections. This model is implemented in the de-excitation model of the generalized evaporation model (GEM), and applied to Monte Carlo spallation reaction simulation using the Particle and Heavy Ion Transport code System (PHITS). Comparing with experimental data for subactinide nuclei shows that this model can provide a unified prediction of the proton-, neutron-, and deuteron-induced fission cross-sections with markedly improved accuracy. The calculated fission fragments tend to shift to higher mass numbers. To account for the isotopic distributions of fission fragments within the framework of a coupled INCL/GEM, modification of INCL would be required, especially for description of the highly excited states of residual nuclei.

Target Optimization Studies for the Spallation Reaction

In the last years, spallation reactions have increasing in several works and research applications. They are applying as optimum neutron sources investigations or for energy production and nuclear-waste transmutation in accelerator-driven systems. In this paper, a series of Monte Carlo calculations using the MCNP-6 code performed to calculate, identify the behavior and number of proton-produced neutrons and photons.

Calculation of the Coulomb barrier and the level density parameter at the fission saddle point in spallation nuclear reactions

This work studies the compound nucleus’ de-excitation during spallation nuclear reactions, with focus on the behavior of the Coulomb barrier for emission of charged particles and the level density parameter at the fission saddle point, establishing for the first time a relationship between these magnitudes and the level density. This relationship manifests itself through two differential equations explicitly dependent on the excitation energy and the level density parameter of the nucleus after the emission of light particles. These equations were implemented into the CRISP code and used to simulate proton induced spallation reactions on and 238U, respectively, comparing the results with data coming from GSI experiments as well as from other codes and obtaining satisfactory results that confirm the reliability of the new models.

Role of breakup processes in deuteron-induced spallation reactions at 100–200 MeV/nucleon

Use of deuteron-induced spallation reactions at intermediate energies has recently been proposed for transmutation of several long-lived fission products (LLFPs). In the design study of a transmutation system using a deuteron primary beam, accurate cross section data of deuteron-induced reactions on the LLFPs are indispensable. Reliable model predictions play an important role in completing the necessary cross section data since currently available experimental data are very limited. Under the circumstances, we have been developing a code system dedicated for deuteron-induced reactions, which is called DEURACS. Aiming to predict the production cross sections of residual nuclei, the purpose of the present work is to clarify a role of deuteron breakup processes in deuteron-induced spallation reactions at intermediate energies. Isotopic production cross sections of residual nuclei in the deuteron-induced reactions on 93Zr and 107Pd at 100-200 MeV/nucleon are analyzed using DEURACS, in which the breakup processes are explicitly taken into account. The calculated cross sections are decomposed into individual components corresponding to the absorption of either neutron or proton in the incident deuteron, or the deuteron itself. The calculated cross sections reproduced the experimental data well over a wide mass number range of residual nuclei. From a component-by-component analysis, it was found that the components of nucleon absorption have the significant contributions to the production of residual nuclei. Consideration of the breakup processes is essential to predict the production cross sections of residual nuclei in deuteron-induced reactions. The framework of DEURACS is applicable to deuteron-induced spallation reactions at intermediate energies.

Excess 180W in IIAB iron meteorites: Identification of cosmogenic, radiogenic, and nucleosynthetic components

The origin of 180W excesses in iron meteorites has been a recently debated topic. Here, a suite of IIAB iron meteorites was studied in order to accurately determine the contribution from galactic cosmic rays (GCR) and from potential decay of 184Os to measured excesses in the minor isotope 180W. In addition to W isotopes, trace element concentrations (Re, Os, Ir, Pt, W) were determined on the same samples, as well as their cosmic ray exposure ages, using 36Cl–36Ar systematics. These data were used in combination with an improved model of GCR effects on W isotopes to correct effects resulting from neutron capture and spallation reactions. After these corrections, the residual 180W excesses correlate with Os/W ratios and indicate a clear contribution from 184Os decay. A newly derived decay constant is equivalent to a half-life for 184Os of (3.38 ± 2.13) × 1013 a. Furthermore, when the data are plotted on an Os–W isochron diagram, the intercept (ε180Wi = 0.63 ± 0.35) reveals that the IIAB parent body was characterized by a small initial nucleosynthetic excess in 180W upon which radiogenic and GCR effects were superimposed. This is the first cogent evidence for p-process variability in W isotopes in early Solar System material.

$\eta$ η and $\omega$ ω mesons as new degrees of freedom in the intranuclear cascade model INCL

The intranuclear cascade model INCL (Liege Intranuclear Cascade) is now able to simulate spallation reactions induced by projectiles with energies up to roughly 15 GeV. This was made possible thanks to the implementation of multipion emission in the NN, $\Delta$ N and $\pi$ N interactions. The results obtained with reactions on nuclei induced by nucleons or pions gave confidence in the model. A next step will be the addition of the strange particles, $\Lambda$ , $\Sigma$ and kaons, in order to not only refine the high-energy modeling, but also to extend the capabilities of INCL, as studying hypernucleus physics. Between those two versions of the code, the possibility to treat the $\eta$ and $\omega$ mesons in INCL has been performed and this is the topic of this paper. Production yields of these mesons increase with energy and it is interesting to test their roles at higher energies. More specifically, studies of $\eta$ rare decays benefit from accurate simulations of its production. These are the two reasons for their implementation. Ingredients of the model, like elementary reaction cross sections, are discussed and comparisons with experimental data are carried out to test the reliability of those particle productions.

Design of imaging system for CSNS near-target beam diagnostics

China Spallation Neutron Source (CSNS) is an accelerator-based pulsed neutron source which produces neutron with spallation reaction induced by proton bombarding tungsten target. With increasing beam powers and influences on target, near-target monitoring becomes extreme necessary. In this situation, an optical imaging system for proton beam diagnostics and monitoring near the target is being developed at CSNS, which can provide real-time images of the beam on target and beam distribution information. In the design of CSNS target imaging system, coating of $$\mathrm{Cr}^{3+}\!\!:\!\mathrm{Al}_{2}\mathrm{O}_{3}$$ is used to convert particle radiation into emission light. According to the geometry limits of CSNS target station, a special optical system was designed and fabricated to collect the emission light. When the proton beams strike on the target, the coating on the target will be excited, emitting luminescence at the same time. The mirrors and lenses of the optical system image the distribution of emission light into a radiation-hard imaging fiber, which transmits the images to the GigE camera located at low-dose area outside of the target station. Software was written on the LabView platform to control the camera and analyze the images on line. Mock-up of the imaging system was manufactured to test and evaluate the performances of the system. Some important characteristics of the system were obtained and studied. Tests on the mock-up of the system present reliably expectation for beam diagnostics. The imaging system has been installed at CSNS recently. More work will be continued to improve the properties of the system.

Nuclide production in spallation reactions: How useful are the simulations?

INCL (Liège IntraNuclear Cascade model) combined with a deexcitation code has been used a lot for numerous simulations of spallation reactions during the last two decades. We go back over some of those simulations to address the capabilities of such codes and to show some improvements. The four examples of simultation are: the EURISOL project, the MEGAPIE target, the ESS facility, and the cosmogenic nuclide production. The goal is to discuss respectively designing and optimisation, predictive power and reliability, feasibility and uncertainty estimate, and the use of modeling to mitigate lack of experimental data.

The predictive power of spallation models for isotopic cross sections

.The experimental cross sections of isotopically identified products of spallation reactions induced by 136Xe projectiles at 1GeV/nucleon on hydrogen target were compared with predictions of a two-step model. The first stage of the reaction was described by the INCL++ model (version 5.3) of an intranuclear cascade of nucleon-nucleon and pion-nucleon collisions whereas the second stage was analyzed by means of four different models; ABLA07, GEM2, GEMINI ++ and SMM. Due to the fact that the experimental data cover a very broad range of elements; from Li(Z=3) to Ba(Z=56) , the analysis could impose severe constraints on the applied reaction models. The quality of data reproduction by the theoretical models is discussed. Some systematic deviations of the theoretical predictions from the experimental results are observed.

Сравнение моделей реакции глубокого расщепления на основе методов многокритериального анализа решений

Сравнение моделей реакции глубокого расщепления на основе методов многокритериального анализа решений

Excitation of baryon resonances in charge-exchange reactions of heavy nuclei

The Liège intranuclear-cascade model (INCL) has been improved using a refined description of the matter and energy densities in the nuclear surface. Hartree-Fock-Bogoliubov calculations with the Skyrme interaction were used to obtain a more realistic description of the proton and neutron density profiles. We find that the new approach, together with a realistic modeling of the de-excitation process of the nuclear pre-fragments, improves the description of the production cross sections of the heaviest nuclear residues produced by charge-exchange processes in spallation reactions, where the excitation of baryonic resonances plays an important role.

Universal odd-even staggering in isotopic fragmentation and spallation cross sections of neutron-rich fragments

An evident odd-even staggering (OES) in fragment cross sections has been experimentally observed in many fragmentation and spallation reactions. However, quantitative comparisons of this OES effect in different reaction systems are still scarce for neutron-rich nuclei near the neutron drip line. By employing a third-order difference formula, the magnitudes of this OES in extensive experimental cross sections are systematically investigated for many neutron-rich nuclei with ($N\ensuremath{-}Z$) from 1 to 23 over a broad range of atomic numbers ($Z\ensuremath{\approx}3--50$). A comparison of these magnitude values extracted from fragment cross sections measured in different fragmentation and spallation reactions with a large variety of projectile-target combinations over a wide energy range reveals that the OES magnitude is almost independent of the projectile-target combinations and the projectile energy. The weighted average of these OES magnitudes derived from cross sections accurately measured in different reaction systems is adopted as the evaluation value of the OES magnitude. These evaluated OES magnitudes are recommended to be used in fragmentation and spallation models to improve their predictions for fragment cross sections.

Proton-induced activation cross section measurement for aluminum with proton energy range from 0.4 to 3 GeV at J-PARC

ABSTRACT We have started an experimental program to measure activation cross sections systematically in the proton-induced spallation reaction in structural materials commonly used in high-intensity proton accelerator-based facilities, such as Japan Proton Accelerator Research Complex (J-PARC). As the first step of the program, aluminum (Al) was chosen to verify the adequacy of the measurement technique implemented in a J-PARC proton beam environment because data of Al have been relatively well studied both by experimental measurement and simulation. Activation cross sections of 7Be, 22Na, and 24Na in Al were measured at proton energy points from 0.4, 1.3, 2.2 to 3.0 GeV, which could be delivered smoothly from the synchrotron. The validity of experimental data has been verified by introducing an effective proton numbers determination procedure. We compared the measured data with existing experimental data, the evaluated data (JENDL-HE/2007), and the calculations with several intra-nuclear cascade models by the Particle and Heavy Ion Transport code System (PHITS) code. Although the experimental data agreed with JENDL-HE/2007, the calculations underestimated about 40%. This could come from the evaporation model (generalized evaporation model) being implemented in the PHITS code. We found that the calculations agreed with the experimental data by an upgraded PHITS code.

Double differential cross section calculations for 16O and 90Zr elements

Double differential cross sections in proton induced reactions on 90Zr and O2 (inert matrix fuel) is calculated at the bombarding energies between 29 and 300 MeV. The proton-induced nuclear reaction cross section data can be used in technical applications such as the isotope production alternatives, spallation reactions for production of neutrons in spallation neutron source, etc. In this study, the cascade excition model including the effect of preequilibrium is used to calculate the differential cross section. Then, the obtained results are discussed and compared with available experimental data.

Integrated Simulation of Fragmentation, Evaporation, and Gamma-decay Processes in the Interaction of Cosmic-ray Heavy Ions with the Atmosphere using PHITS

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Pairing-energy coefficients of neutron-rich fragments in spallation reactions**Supported by National Natural Science Foundation of China (U1732135), Natural Science Foundation of Henan Province (162300410179) and Henan Normal University for the Excellent Youth (154100510007)

The ratio of pairing-energy coefficient to temperature (ap/T) of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5A and 1A GeV 208Pb + p, 1A GeV 238U + p, 0.5A GeV 136Xe + d, 0.2A, 0.5A and 1A GeV 136Xe + p, and 56Fe + p with incident energy ranging from 0.3A to 1.5A GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess (I ≡ N-Z), and in the relatively small-A fragments which have large I. The values of ap/T for the fragments, with I from 0 to 36, have been found to be in a range from −4 to 4, and most values of ap/T fall in the range from −1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with A/As > 85% (where As is the mass number of the spallation system).

An evaluation of activation and radiation damage effects for the European Spallation Source Target

ABSTRACT The details concerning the generation and accumulation of radionuclides produced by spallation reactions within the neutron generation target to be installed at the European Spallation Source are described. The resulting radiation damage for the target tungsten blocks constituents as well as the target encasing is evaluated and explicit results are given for the effects of knock-on atoms as well as those resulting from the accumulation of light and volatile hydrogen and helium isotopes resulting from spallation reactions. Their effects on the mechanical properties are discussed on the light of available experimental data and, on this basis, an estimation of the target lifetime is given.

Spallation reaction study for the long-lived fission products in nuclear waste: Cross section measurements for 137Cs, 90Sr and 107Pd using inverse kinematics method

Spallation reaction study has been performed for the long-lived fission products 137Cs, 90Sr and 107Pd. Isotopic cross sections on proton and deuteron were obtained by using the inverse kinematics technique at the RIKEN Radioactive Isotope Beam Factory. It was found that the deuteron-induced cross sections are larger than the proton-induced ones for the light-mass products. The experimental data were compared with the SPACS semi-empirical parameterization and a theoretical calculation including both the intra-nuclear cascade and evaporation models by the PHITS transport code. It was found that the spallation reaction could be a promising mechanism for the transmutation of 137Cs and 90Sr due to the large total cross section.

Recent progress in nuclear data measurement for ADS at IMP

Recent progress in nuclear data measurement for ADS at Institute of Modern Physics is reviewed briefly. Based on the cooler storage ring of the Heavy Ion Research Facility in Lanzhou, nuclear data terminal was established. The nuclear data measurement facility for the ADS spallation target has been constructed, which provides a very important platform for the experimental measurements of spallation reactions. A number of experiments have been conducted in the nuclear data terminal. A Neutron Time-of-Flight (NTOF) spectrometer was developed for the study of neutron production from spallation reactions related to the ADS project. The experiments of 400 MeV/u 16O bombarded on a tungsten target were presented using a NTOF spectrometer. Neutron yields for 250 MeV protons incident on a thick grain-made tungsten target and a thick solid lead target have been measured using the water-bath neutron activation method. Spallation residual productions were studied by bombarding W and Pb targets with a 250 MeV proton beam using the neutron activation method. Benchmarking of evaluated nuclear data libraries was performed for D-T neutrons on ADS relevant materials by using the benchmark experimental facility at the China Institute of Atomic Energy.