Spallation Reactions Research Articles

Recovery of no-carrier-added 41Ca, 44Ti, and 26Al from high-energy proton-irradiated vanadium targets

Abstract Many useful and needed radionuclides for medicinal, astrophysical, and environmental research are produced naturally in inefficient quantities or not-at-all. In the method described here, rare cosmogenic isotopes were produced via spallation reactions in metallic vanadium and separated without adding any carriers. In the SINQ facility at the Paul Scherrer Institut, the vanadium targets were irradiated for two years with high-energy protons (≤590 MeV). After a cooling period of eight years, only relatively long-lived radionuclides such as 32Si, 44Ti, 41Ca, and 26Al remain present. After target dissolution, 32Si was first separated for a prospective half-life redetermination. The remaining 32Si-free solution was used for extracting 44Ti, 41Ca, and 26Al, three key isotopes which are scientifically interesting for nuclear astrophysics research as well as medical applications. Each separation scheme employed ion-exchange and extraction chromatography; developed and optimized using inactive model solutions analyzed with Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES). The irradiated samples were tracked with γ-ray spectroscopy for γ-ray emitting impurities. As a result, radiochemically pure sample solutions of 44Ti, 41Ca, and 26Al were obtained as “ready for use” in different application fields.

Application of the improved quasi-static coupled probability theory method to transient safety analysis of an experimental facility

The accelerator-driven sub-critical system is driven by external neutron sources, which are generated by the spallation reaction and maintain the stable operation of the sub-critical core, while the external neutron source increases the complexity of reactor neutron kinetic processes. This article focuses on simulation analysis of neutron space–time kinetics with a dynamic analysis code, which is developed based on the improved quasi-static approximation and Monte Carlo neutron transport method. The amplitude function and shape functions are solved to achieve the dynamics simulation process. Then, the transient responses of beam interruptions and reactivity insertions are calculated and analyzed for an experimental facility. To further verify the correctness and reliability of dynamic behavior, the simulation results are compared with experimental values, and the results show that the normalized neutron fluxes varying with time are in good agreement with the corresponding values. It can be concluded that the improved quasi-static coupled probability theory method can be used to solve the neutron space–time kinetic problem of the experimental facility, and the results are reliable.

Testing hadronic and photo-hadronic interactions as responsible for UHECR and neutrino fluxes from Starburst Galaxies

We test the hypothesis that starburst galaxies are the sources of ultra-high energy cosmic rays and high-energy neutrinos. The computation of interactions of ultra-high energy cosmic rays in the starburst environment as well as in the propagation to the Earth is made using a modified version of the Monte Carlo code SimProp, where hadronic processes are implemented for the first time. Taking into account a star-formationrate distribution of sources, the fluxes of ultra-high energy cosmic rays and high-energy neutrinos are computed and compared with observations, and the explored parameter space for the source characteristics is discussed. We find that, depending on the density of the gas in the source environment, spallation reactions could hide the outcome in neutrinos from photo-hadronic interactions in the source environment and in extra-galactic space. We confirm that source-propagation models constitute a promising way to improve the discrimination power of models considering only ultra-high energy cosmic rays, on the way to unveiling the source class responsible for ultra-high energy cosmic rays and high-energy neutrinos.

Spallation reaction study to improve cross-section measurements of fission products in nuclear waste using Cs-137 on proton or deuteron ranging from 0.1 to 2.4 GeV

Spallation reaction study to improve cross-section measurements of fission products in nuclear waste using Cs-137 on proton or deuteron ranging from 0.1 to 2.4 GeV

Spallation reaction study to improve cross-section measurements of fission products in nuclear waste using Cs-137 on proton or deuteron ranging from 0.1 to 2.4 GeV

Spallation reaction study to improve cross-section measurements of fission products in nuclear waste using Cs-137 on proton or deuteron ranging from 0.1 to 2.4 GeV

Study on Using Microbubbles to Reduce Surface Damage of Mercury Target for Spallation Neutron Source

A liquid mercury target, which is used to explore the neutrons produced by spallation reactions, has been installed at the Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). As the proton beams bombard the target, pressure waves are generated on the interface between liquid and solid metals due to thermal shock. The negative-pressure-induced cavitation causes severe pitting damage to the vessel surface of the mercury target. To reduce the surface damage of the mercury target and prolong its service life, we developed vibratory horn experiments in bubbly water. In this study, the effect of microbubbles on cavitation damage on the workpiece surface was investigated using ultrasonic erosion tests. Experimental results showed that surface damage was significantly reduced under the condition of injecting microbubbles. Additionally, we developed a simulation code to analyze the change in pressure waves in the water. The analysis results showed that the pressure amplitude of the pressure waves was significantly reduced under the condition of injecting microbubbles, and the fluctuation of the pressure waves became more regular when injecting microbubbles. We also found that the pressure amplitude of the pressure waves was decreased with a decrease in the diameter of the microbubbles.

Research of spallation reaction on plutonium target irradiated by protons with energy of 660 MeV

Relevance. This paper describes the measurement of the cross sections of the fission and fragmentation reactions of a plutonium target irradiated with a series of protons characterized by an energy of 660 MeV at the Phazotron accelerator of the Joint Institute for Nuclear Research. Purpose. The experiment focuses on the determination of short-lived radionuclides. Methods. The experimental sample was measured in offline mode using gamma spectrometry with HPGe detector. The reaction rates of the formed residual nuclei were studied. The products of spallation reaction were determined with the help of the direct kinematics method. The DEIMOS32 software was used to process γ-spectra. Results. As a result of the interaction of nuclear elements with protons, nuclei were formed in the 239Pu sample. Those nuclei were identified using the TJ02000321–V3 software. The reaction products were identified based on gamma energies, intensity and half-life after the measurement set. During the study of the gamma spectra determined for the irradiated plutonium target, it was possible to establish 50 gamma lines and reveal 31 nuclides by energy and half-life cycles from 14.4 m to 3.19 h. The measured nuclear reaction cross-sections can serve as reference data for theoretical simulations of the interaction of protons with 239Pu and they can be a supplement to the nuclear databases. Conclusions. The obtained experimental result is compared with the simulation on MCNP 6.1. The data overall correspond to the expected range, but it still needs more evaluation. The next logical step is to search for primary products (mother nuclei) and compare the obtained experimental data with the results of computer simulations

The SINQ gas-jet facility as a source for radionuclides from neutron-induced fission of 235U

The Swiss Spallation Neutron Source SINQ of the Paul Scherrer Institute provides neutrons via proton-induced spallation reactions in a lead target. Produced neutrons are thermalized and impinge on 235U-targets, enclosed in a three-part chamber assembly, which is located in the inner wall of the SINQ shielding. The thermal-neutron-induced fission products can be readily transported from this chamber assembly to a radiochemical laboratory using the gas-jet technique either with a pure carrier gas or with an aerosol-particle-loaded carrier gas. In the past, mainly radioisotopes of the elements Se, Br, Rb, and Kr were retrieved and used for gas-phase chemistry experiments. Here, we present first experiments after the commissioning of the SINQ gas-jet facility as a source of recoverable, non-volatile and volatile, carrier-free fission products for general radiochemical studies and other applications.

Measurement of nuclide production cross sections for proton-induced reactions on [formula omitted]Ni and [formula omitted]Zr at 0.4, 1.3, 2.2, and 3.0 GeV

Nuclide production cross sections for proton-induced reactions on natNi and natZr at incident energies of 0.4, 1.3, 2.2, and 3.0 GeV were measured by the activation method at Japan Proton Accelerator Research Complex (J-PARC). In total, 24 and 43 residual nuclides were measured for the natNi and natZr targets, respectively. Among them, the cross sections of the following reactions were measured for the first time: natZr(p,x)28Mg, natZr(p,x)42K, natZr(p,x)43K, natZr(p,x)44gSc, natZr(p,x)55Co, natZr(p,x)69mZn, and natZr(p,x)93Y reactions. To examine the prediction capabilities, the measured data were compared with the spallation reaction models in PHITS (INCL4.6, Bertini, and JAM as intranuclear cascade models, and GEM as an evaporation model), INCL++/ABLA07, semi-empirical calculation code SPACS, and the JENDL/HE-2007 library. From the evaluation introducing the mean square deviation factor, the best reproducibility was exhibited by the JENDL/HE-2007 library for natNi and INCL++/ABLA07 for natZr.

Role of low-lying resonances for the Be10(p,α)Li7 reaction rate and implications for the formation of the Solar System

Evidence for the presence of short-lived radioactive isotopes when the Solar System formed is preserved in meteorites, providing insights into the conditions at the birth of our Sun. A low-mass core-collapse supernova had been postulated as a candidate for the origin of $^{10}$Be, reinforcing the idea that a supernova triggered the formation of the Solar System. We present a detailed study of the production of $^{10}$Be by the $\nu$ process in supernovae, which is very sensitive to the reaction rate of the major destruction channel, $^{10}$Be(p,$\alpha$)$^{7}$Li. With data from recent nuclear experiments that show the presence of a resonant state in $^{11}$B at $\approx$~193 keV, we derive new values for the $^{10}$Be(p,$\alpha$)$^{7}$Li reaction rate which are significantly higher than previous estimates. We show that, with the new $^{10}$Be(p,$\alpha$)$^{7}$Li reaction rate, a low mass CCSN is unlikely to produce enough $^{10}$Be to explain the observed $^{10}$Be/ $^{9}$Be ratio in meteorites, even for a wide range of neutrino spectra considered in our models. These findings point towards spallation reactions induced by solar energetic particles in the early Solar System as the origin of $^{10}$Be.

FLUKA cross sections for cosmic-ray interactions with the DRAGON2 code

Secondary particles produced in spallation reactions of cosmic rays with the interstellar gas provide valuable information that allow us to investigate the injection and transport of charged particles in the Galaxy. A good understanding of the cross sections of production of these particles is crucial to correctly interpret our models, although the existing experimental data is very scarce and uncertain. We have developed a new set of cross sections, both inelastic and inclusive, computed with the FLUKA Monte Carlo nuclear code and tested its compatibility with CR data. Inelastic and inclusive cross sections have been compared to the most up-to-date data and parameterisations finding a general good agreement.Then, these cross sections have been implemented in the DRAGON2 code to characterize the spectra of CR nuclei up to Z = 26 and the secondary-to-primary ratios of B, Be and Li. Interestingly, we find that the FLUKA cross sections allow us to predict an energy-dependence of the B, Be and Li flux ratios which is compatible with AMS-02 data and to reproduce simultaneously these flux ratios with a scaling lower than 20%. Finally, we implement the cross sections of production of gamma rays, calculated with FLUKA, in the Gammasky code and compute diffuse gamma-ray sky maps and the local HI emissivity spectrum, finding a very good agreement with Fermi Large Area Telescope data.

Bayesian evaluation of residual production cross sections in proton-induced nuclear spallation reactions

Residual production cross sections in spallation reactions are key data for nuclear physics and related applications. Spallation reactions are very complex due to the wide range of incident energies and abundant fragments involved. Therefore, it is challenging to obtain accurate and complete energy-dependent residual cross sections. With the guidance of a simplified EPAX formula (sEPAX), the Bayesian neural network (BNN) technique is applied to form a new machine learning model (BNN + sEPAX) for predicting fragment cross sections in proton-induced nuclear spallation reactions. Three types of sample dataset for measured residual production cross sections in proton-induced nuclear spallation reactions are made, i.e. D1 consists of isotopic cross sections in reactions below 1 GeV/u, D2 consists of fragments excitation functions of reactions up to 2.6 GeV/u, and D3 is a hybrid of D1 and D2. With the constructed BNN and BNN + sEPAX models, the isotopic and mass cross section distributions are compared for the 356 MeV/u 40Ca + p and 1 GeV/u 136Xe + p reactions, and fragment excitation functions in 40Ca + p, 56Fe + p, 138Ba + p and 197Au + p reactions. It is found that the BNN model needs sufficient information to achieve good extrapolations, while the BNN + sEPAX model performs better extrapolations based on less information due to the physical guidance of the sEPAX formulas. It is suggested that the BNN + sEPAX model provides a new approach to predict the energy-dependent residual production cross sections produced in proton-induced nuclear spallation reactions of incident energies from tens of MeV/u up to several GeV/u.

Target dependence of isotopic cross sections in the spallation reactions 238U + p, d and 9Be at 1 AGeV * *Supported by the National Natural Science Foundation of China (11875328, 12075327)

The spallation of 238U is an important way to produce rare isotopes. This work aims at studying the cross sections of isotopes produced in 238U + p, d and 9Be reactions at 1 A GeV and their target dependence. (1) A physical model dependent (Bayesian neural network) BNN, which includes the details of IQMD-GEMINI++ model and BNN, was developed for a more accurate evaluation of production cross sections. The isospin-dependent quantum molecular dynamics (IQMD) model is used to study the non-equilibrium thermalization of the 238U nuclei and fragmentation of the hot system. The subsequent decay of the pre-fragments is simulated by the GEMINI++ model. The BNN algorithm is used to improve the prediction accuracy after learning the residual error between experimental data and calculations by the IQMD-GEMINI++ model. It is shown that the IQMD-GEMINI++ model can reproduce the available experimental data (3282 points) within 1.5 orders of magnitude. After being fine tuned by the BNN algorithm, the deviation between calculations and experimental data were reduced to within 0.4 order of magnitude. (2) Based on the predictions by the IQMD-GEMINI++-BNN framework, the target dependence of isotopic cross sections was studied. The cross sections to produce the rare isotopes by the 238U + p, d and 9Be reactions at 1 A GeV are compared. For the generation of neutron-rich fission products, the cross sections for the 238U + 9Be are the largest. For the generation of neutron-deficient nuclei in the region of A = 200–220, the cross sections for 238U + p reaction are the largest. Considering the largest cross sections and the atomic density, the beryllium target is recommended to produce the neutron-rich fission products by the 238U beam at 1 A GeV, while the liquid-hydrogen target is suggested to produce the neutron-deficient nuclei in the region of A = 200–220.

Possible solution to the triple alpha fine-tuning problem: Spallation reactions during planet formation

Carbon is produced during the helium burning phase of sufficiently massive stars through the triple alpha process. The 0+ energy level of the carbon nucleus allows for resonant nuclear reactions, which act to greatly increase the carbon yields compared to the non-resonant case. Many authors have argued that small changes to the energy level of this resonance would lead to a significantly lower carbon abundance in the universe, and this sensitivity is often considered an example of fine-tuning. By considering spallation reactions occurring during the process of planet formation, this paper presents a partial solution to this triple alpha fine-tuning problem. Young stellar objects generate substantial luminosities of particle radiation (cosmic rays) that can drive nuclear reactions through spallation. If the standard triple alpha process is inoperative, stars tend to synthesize oxygen (and other alpha elements) rather than carbon. Cosmic rays can interact with oxygen nuclei to produce carbon while planets are forming. The resulting carbon abundances are significant, but much smaller than those observed in our universe. However, for a range of conditions – as delineated herein – spallation reactions can result in carbon-to-oxygen ratios roughly comparable to those found on Earth and thereby obviate the triple alpha fine-tuning problem.

ENVIRONMENTAL LEVELS OF RADIOCARBON IN LUND, SWEDEN, PRIOR TO THE START OF THE EUROPEAN SPALLATION SOURCE

ABSTRACTThe European Spallation Source (ESS) is a neutron-based research facility under construction in Lund in southern Sweden. The spallation reactions will generate not only the desired neutrons, but also many radioactive by-products, including 14C. As part of the licensing process, and as recommended by the IAEA, various preoperational studies are being carried out, including mapping the “zero-point” radiation environment around the site. As the city of Lund hosts several facilities using 14C-labeled substances, and since temporary and local 14C contamination have been observed in the past, 14C mapping is an important part of these baseline assessments. We here present a summary of 14C levels in various terrestrial environmental samples in Lund and in southern Sweden during the years 2012 to 2020. These environmental F14C do not display significantly elevated levels compared to sites located remote from Lund. We also describe a local 14C contamination event that was detected at the Lund Radiocarbon Dating Laboratory in 2009. Horse-chestnut leaves collected close to the laboratory exhibited F14C values of up to ∼25% above the clean air background. Elevated values of F14C were also found in a short tree-ring series, especially in 2007. The source of this contamination was identified and successfully removed.

Hypernuclei formation in spallation reactions by coupling the Liège intranuclear cascade model to the deexcitation code ABLA

Innovative experiments using the inverse kinematics technique to accelerate light, medium-mass, and heavy nuclei at relativistic energies have become excellent tools to produce and study hypernuclei. We investigate hypernuclei created in spallation reactions, where multifragmentation, particle evaporation, and fission processes play an important role in the formation of final hypernuclei residues. For the description of spallation reactions, we couple the Li\`ege intranuclear cascade model, extended recently to the strange sector, to a new version of the ablation (ABLA) model that accounts for the evaporation of $\mathrm{\ensuremath{\Lambda}}$ particles from hot hyperremnants produced during the intranuclear cascade stage. These state of the art models are then used to study the production of hypernuclei close to drip lines through spallation-evaporation and fission reactions.

Isotopic cross section measurement of the nuclear spallation reaction

Isotopic cross section measurement of the nuclear spallation reaction

Numerical investigation of spallation neutrons generated from petawatt-scale laser-driven proton beams

Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration. We examine this through particle-in-cell and Monte Carlo simulations that model, respectively, the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets. Laser parameters relevant to the 0.5 PW LMJ-PETAL and 0.6–6 PW Apollon systems are considered. Owing to its high intensity, the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100 MeV, thereby unlocking efficient neutron generation via spallation reactions. As a result, despite a 30-fold lower pulse energy than the LMJ-PETAL laser, the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux. Notably, we predict that very compact neutron pulses, of ∼10 ps duration and ∼100 μm spot size, can be released provided the lead convertor target is thin enough (∼100 μm). These sources are characterized by extreme fluxes, of the order of 1023 n cm−2 s−1, and even ten times higher when using the 6 PW Apollon laser. Such values surpass those currently achievable at large-scale accelerator-based neutron sources (∼1016 n cm−2 s−1), or reported from previous laser experiments using low-Z converters (∼1018 n cm−2 s−1). By showing that such laser systems can produce neutron pulses significantly brighter than existing sources, our findings open a path toward attractive novel applications, such as flash neutron radiography and laboratory studies of heavy-ion nucleosynthesis.

Formula omitted]Pb(p,x)194Hg and 209Bi(p,x)194Hg excitation functions in the energy range 0.04–2.6 GeV

The article presents the excitation functions of 194Hg, which is formed in Pb–Bi eutectic, on lead and bismuth isotopes in deep spallation reactions. The 194Hg production cross sections were measured by direct gamma spectrometry in lead targets enriched in 208Pb, 207Pb, and 206Pb, respectively, as well as in natural lead and bismuth, irradiated with protons of 11 energies from 0.04 to 2.6 GeV. Where possible, the experimental data are compared with the data of other authors, as well as with the simulated excitation functions of this nuclide, obtained using various high-energy transport codes - MCNP6.1 (CEM03.03), PHITS (INCL4.6/GEM), Geant4 (INCL++/ABLA) and the TENDL-2019 data library evaluation.

Measurement of nuclide production cross sections for proton-induced reactions on Mn and Co at 1.3, 2.2, and 3.0 GeV

Nuclide production cross sections for proton-induced reactions on Mn and Co at incident energies of 1.3, 2.2, and 3.0 GeV were measured by the activation method at the Japan Proton Accelerator Research Complex (J-PARC). In total, 143 production cross sections of reaction products with half-lives ranging from 1.8 h to 2.6 yr were obtained. Among them, the cross sections of 55Mn(p,x)38S, 55Mn(p,x)41Ar, and 59Co(p,x)38S reactions were measured for the first time. The stable proton beam and well-established beam profile-motoring system contributed to the reduction of the systematic uncertainties to typically less than 5%, which was better than those of the previous data (typically ∼10%). To examine the prediction capabilities of spallation reaction models and evaluated nuclear data library, the measured data were compared with the spallation reaction models in PHITS (INCL4.6, Bertini, and JAM as intranuclear cascade models, and GEM as an evaporation model), INCL++/ABLA07, and the JENDL/HE-2007 library. The comparison of the mean square deviation factors indicated that both INCL4.6/GEM and JENDL/HE-2007 showed better agreement with the measured data than the others.