Search

The capabilities of the new version of the Li\`ege intranuclear cascade model (labeled $\mathrm{INCL}++6$ from now on) are presented in detail. This new version of INCL is able to handle strange particles, such as kaons and the $\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{\ensuremath{\Sigma}}$ hyperons, and the associated reactions and also allows extending nucleon-nucleon collisions up to about $15\text{--}20$ GeV incident energy. Compared to the previous version, new observables can be studied, e.g., kaon, hyperon, and hypernuclei production cross sections (with the use of a suitable de-excitation code) as well as aspects of kaon-induced spallation reactions. The main purpose of this paper is to present the specific ingredients of the new INCL version and its new features, notably the newly implemented variance reduction scheme. We also compare, for some illustrative strangeness production cases, theoretical results calculated using this version of INCL with experimental data.

Motivated by a renewed interest in studies of hypernuclei, the strangeness degree of freedom was implemented in the intranuclear cascade model INCL. This model takes care of the first stage of reactions between a nucleon (or a light cluster) and a nucleus at energies from a few tens of MeV up to a few GeV. After emission of fast particles, a hot remnant nucleus is produced and another model, combined to INCL, handles the de-excitation (Abla in our case). The main ingredients are discussed and we compare the results to experimental data.

We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the n_TOF lead spallation target, irradiated with 20 GeV/c protons, neutral pions are involved in the production of ~90% of the high-energy photons; charged pions participate in ~40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets., Comment: 17 pages, 14 figures. Submitted to Eur. Phys. J. A

The intranuclear cascade model INCL (Li\`ege 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., Comment: 22 pages, 17 figures, submitted to EPJ Plus

International audience; Motivated by a renewed interest in studies of hypernuclei, the strangeness degree of freedom was implemented in the intranuclear cascade model INCL. This model takes care of the first stage of reactions between a nucleon (or a light cluster) and a nucleus at energies from a few tens of MeV up to a few GeV. After emission of fast particles, a hot remnant nucleus is produced and another model, combined to INCL, handles the de-excitation (the Abla model in our case). The main ingredients will be discussed and we will compare the results to experimental data. The experimental kaon spectra for different target elements and at different energies agree reasonable well with the model predictions. The main remaining discrepancies are analysed and will be explained.

International audience; The production of strange particles (kaons, hyperons) and hypernuclei in light charged-particle-induced reactions in the energy range of a few GeV (2-15 GeV) has become a topic of active research in several facilities (e.g., HypHI and PANDA at GSI and/or FAIR (Germany), JLab (USA), and JPARC (Japan)). This energy range represents the low-energy limit of the string models (degree of freedom: quark and gluon) or the high-energy limit of the so-called spallation models (degree of freedom: hadrons). A well-known spallation model is INCL, the Liège intranuclear cascade model (combined with a de-excitation model to complete the reaction). INCL, known to give good results up to 2-3GeV, was recently upgraded by the implementation of multiple pion emission to extend the energy range of applicability up to roughly 15GeV. The next step, to account also for strange particle production, both for refining the high-energy domain and making it usable when strangeness appears, requires the following main ingredients: i) the relevant elementary cross sections (production, scattering, and absorption) and ii) the characteristics of the associated final states. Some of those ingredients are already known and, sometimes, already used in models of the same type (e.g., Bertini, GiBUU), but this paper aims at reviewing the situation by compiling, updating, and comparing the necessary elementary information which are independent of the model used.

International audience; 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.

The residual nuclei produced in the spallation reaction of Xe-136 nuclei at 200A MeV on protons have been studied by measuring the isotopic distributions for the elements from cadmium (Z = 48) to cesium (Z = 55) by using the fragment separator (FRS) spectrometer at GSI and the inverse kinematics technique. This is one of the few measurements performed at such a low projectile energy, close to the validity limit for intranuclear cascade models such as INCL or ISABEL. The experimental results have been compared to these intranuclear cascade codes coupled to the evaporation code ABLA. Both code combinations reproduce qualitatively the measured isotopic distributions; however, both underestimate the production of residues with mass numbers between 126 and 134. The measured cross sections are of interest for the planning of future radioactive beam or neutron source facilities.

International audience; The residual nuclei produced in the spallation reaction of $^{136}$Xe nuclei at 200A MeV on protons have been studied by measuring the isotopic distributions for the elements from cadmium (Z=48) to cesium (Z=55) by using the fragment separator (FRS) spectrometer at GSI and the inverse kinematics technique. This is one of the few measurements performed at such a low projectile energy, close to the validity limit for intranuclear cascade models such as incl or isabel. The experimental results have been compared to these intranuclear cascade codes coupled to the evaporation code abla. Both code combinations reproduce qualitatively the measured isotopic distributions; however, both underestimate the production of residues with mass numbers between 126 and 134. The measured cross sections are of interest for the planning of future radioactive beam or neutron source facilities.

International audience; The prediction of one-nucleon-removal cross sections by the Liège intranuclear-cascade model 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 are used to obtain a more realistic description of the radial-density distributions of protons and neutrons, as well as the excitation-energy uncorrelation at the nuclear surface due to quantum effects and short-range correlations. The results are compared with experimental data covering a large range of nuclei, from carbon to uranium, and projectile kinetic energies. We find that the new approach is in good agreement with experimental data of one-nucleon-removal cross sections covering a broad range in nuclei and energies. The new ingredients also improve the description of total reaction cross sections induced by protons at low energies, the production cross sections of heaviest residues close to the projectile, and the triple-differential cross sections for one-proton removal. However, other observables such as quadruple-differential cross sections of coincident protons do not present any sizable sensitivity to the new approach. Finally, the model is also tested for light-ion-induced reactions. It is shown that the new parameters can give a reasonable description of the nucleus-nucleus total reaction cross sections at high energies.

We proposed a new nuclear reaction model in combination of Intra-Nuclear Cascade of Liege (INCL) and the Distorted Wave Born Approximation (DWBA) calculation, and incorporated it into the Particle and Heavy Ion Transport code System (PHITS). This model was applied to deuteron induced reactions on nat Li and 9 Be targets for deuteron incident energies of 40 and 18 MeV, respectively. Double-differential cross sections and neutron yields on thick targets obtained by PHITS using the model reproduce experimental data quite well.

The experiment was performed at the GSI facility in Darmstadt (Germany).; Around 270 medium-mass residual nuclei, formed in spallation reactions induced by 136Xe projectiles impinging on a liquid hydrogen target at 500 AMeV, have been unambiguously identified at GSI using the magnetic spectrometer FRS. The individual production cross sections and the longitudinal momentum distributions have been determined with high accuracy. These data represent an important constraint for theoretical models describing spallation reactions.

We present INCL intra-nuclear cascade and ABLA de-excitation (evaporation/fission) models that can be used to calculate collisions between projectile particles and nuclei at energies from 0.2 to 3 GeV. Supported projectiles are proton, neutron, pions and light ions up to alpha. The optimal target materials range from carbon to uranium. We have extended the INCL model light ion projectile support up to carbon-ions and compared the results against thin and thick target data and Geant4 Binary cascade model. Both thin and first thick target results of the INCL model are in good agreement with experimental data.

Radiation hazard for space missions is mainly due to cosmic ray protons, helium nuclei and light ions, whose energy spectrum is maximum around 1 GeV per nucleon but remains non-negligible for energies up to 15 GeV per nucleon. Nuclear reactions induced by high energy protons are often described by intranuclear cascade plus evaporation models. The attention is focused here on the Liege Intranuclear Cascade model (INCL), which has been shown to reproduce fairly well a great deal of experimental data for nucleon-induced reactions in the 200 MeV to 2 GeV range, when coupled with the ABLA evaporation-fission code. In order to extend the model to other conditions relevant for space radiation, three improvements of INCL are under development. They are reported on here. First, the reaction model has been extended to nucleon–nucleus reactions at incident energies up to 15 GeV, mainly by the inclusion of additional pion production channels in nucleon–nucleon collisions during the cascade. Second, a coalescence mechanism for the emission of light charged particles has been implemented recently. Finally, the model has been modified in order to accommodate light ions as projectiles. First results are shown and compared with illustrative experimental data. Implications for issues concerning radiation protection in space are discussed.

The composition of the space radiation environment inside spacecrafts is modified by the interaction with shielding material, with equipment and even with the astronauts' bodies. Accurate quantitative estimates of the effects of nuclear reactions are necessary, for example, for dose estimation and prediction of single-event-upset rates. To this end, it is necessary to construct predictive models for nuclear reactions, which usually consist of an intranuclear-cascade or quantum-molecular-dynamics stage, followed by a nuclear-de-excitation stage. While it is generally acknowledged that it is necessary to accurately simulate the first reaction stage, transport-code users often neglect or underestimate the importance of the choice of the de-excitation code. The purpose of this work is to prove that the de-excitation model is in fact a non-negligible source of uncertainty for the prediction of several observables of crucial importance for space applications. For some particular observables, the systematic uncertainty due to the de-excitation model actually dominates the total uncertainty. Our point will be illustrated by making use of nucleon-nucleus calculations performed with several intranuclear-cascade/de-excitation models, such as the Li\`{e}ge Intranuclear Cascade model (INCL) and Isabel (for the cascade part) and ABLA07, Dresner, GEM, GEMINI++ and SMM (on the de-excitation side)., Comment: 12 pages, 6 figures. Presented at the 38th COSPAR Scientific Assembly (Bremen, Germany, 18-25 July 2010). Submitted to Advances in Space Research

Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at SIS. Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed., Comment: 7 pages, 4 figures, contribution to proceedings of International School of Nuclear Physics, 30th Course, Heavy-Ion Collisions from the Coulomb Barrier to the Quark-Gluon Plasma, Erice-Sicily: 16 - 24 September 2008

A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory. Searching for signals of criticality in the fragment production we have applied the model independent universal fluctuations theory already proposed to track criticality signals in multifragmentation to our data. The fluctuation of the largest fragment charge and of the asymmetry of the two and three largest fragments and their bimodal distribution have also been analysed., Comment: 6 pages, 4 figures, IX International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, Brazil, August 28 - September 1, 2006

Residual fragment production in reactions induced by $^{136}\mathrm{Xe}$ projectiles impinging on a liquid deuterium target at $500A$ MeV has been measured at GSI. Projectile residues were unambiguously identified in atomic and mass numbers using the Fragment Separator as high-resolution zero-degree spectrometer. The isotopic production yields of these residuals were used to benchmark reference model calculations describing spallation reactions. In particular the energy dissipated in these reactions was assessed by comparing the production yields measured in this work with the ones obtained in reactions induced by $^{136}\mathrm{Xe}$ projectiles on protons at $1000A$ and $500A$ MeV.

Spallation reactions on fissile nuclei represent an appropriate tool to investigate dissipative effects in nuclear fission. In this work, we have studied transient and dissipative effects in proton- and deuteron-induced fission on Pb208 at 500A MeV. A dedicated experimental setup optimized for inverse kinematics measurements made it possible to identify in atomic number both fission fragments with high resolution, and reconstruct the charge of the fissioning system. We could then determine the width of the fission fragments charge distribution as well as partial fission cross sections, both as a function of the charge of the fissioning system. These two complementary observables permitted us to investigate the dynamics of the process at small deformation, i.e., from the ground state to the saddle point. The description of these observables with advanced model calculations reveals the influence of the nuclear dissipation in the fission process at high excitation energy and in particular its manifestation through transient time effects.

International audience; It is a well-established fact that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one-nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons for this deficiency. We find that a refined description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables, and that neither ingredient is sufficient if taken separately. As a by-product, the predictions for removal of several nucleons are also improved by the refined treatment.

New improvements of the INCL4 cascade model, bearing on cluster production, nucleon and pion potentials and Pauli blocking at low energy, are reviewed.

PACS conv.GSI; The isotopic distributions and recoil velocities of the fission fragments produced in the spallation reaction 208Pb + p at 500 A MeV have been measured using the inverse-kinematics technique, a lead beam onto a liquid-hydrogen target, and the high-resolution spectrometer FRS at GSI. The shapes of the different distributions are found in good agreement with previously published data while the deduced total fission cross-section is higher than expected from existing systematics and some previous measurements. From the experimental data, the characteristics of the average fissioning system can be reconstructed in charge, mass and excitation energy, and the average number of post-fission neutrons can be inferred. The results are also compared to different models describing the spallation reaction. The intranuclear cascade code INCL4 followed by the de-excitation code ABLA is shown to describe reasonably well the evolution of the isotopic distribution shapes between 500 and 1000 A MeV.

A model is proposed to describe emission of light charged clusters during the cascade stage in nucleon-induced spallation reactions. It consists in implementing a surface percolation procedure into the Liege intranuclear cascade (INCL4) model: when a nucleon is ready to leave the nuclear surface, it is allowed to drag along a cluster of nucleons, under some conditions of closeness in phase space. This possibility relies on the instantaneous dynamical phase space occupancy in the nuclear surface. The following clusters are considered: d,t, 3 He , 4 He . Good agreement is obtained with experimental data relative to heavy and medium-heavy targets at two different energies. It is shown that the implementation of light cluster emission in the cascade stage also improves our previous results for residue mass spectra.

Fission fragments from 1 A GeV 238U projectiles irradiating a hydrogen target were investigated by using the fragment separator FRS for magnetic selection of reaction products including ray-tracing and DE-ToF techniques. The momentum spectra of 733 identified fragments were analysed to provide isotopic production cross sections, fission-fragment velocities and recoil momenta of the fissioning parent nuclei. Besides their general relevance, these quantities are also demanded for applications. Calculations and simulations with codes commonly used and recently developed or improved are compared to the data., Comment: 60 pages, 21 figures, 4 tables, 2 appendices (15 pages)

In high-energy transport codes used to design Accelerator Driven Systems or spallation neutron sources, elementary interactions are computed through nuclear physics models. Among these, Intra-Nuclear Cascade models play a major role since the excitation energy at the end of the INC stage determines the number of evaporated particles. Therefore, in simulation of spallation targets, INC influences the total number of emitted neutrons and the isotopic distribution of produced nuclei. Recent data regarding the production of neutrons and residual nuclei in proton induced reactions make it possible to test the reliability of INC models and to improve them. A new version (INCL4) of the Liege INC model including especially a realistic nuclear density and a consistent treatment of the Pauli principle is presented.

With the inverse kinematics method, the reaction mechanism which leads to the formation of light nuclides was investigated with a 1 A GeV 238 U beam impinging on a liquid H 2 target. Isotopes of all elements with Z ⩾6 were unambiguously identified, and the velocity of every produced nuclide was measured with great precision. Results show that very asymmetric fission of uranium nuclei produces neutron-rich isotopes of elements down to around charge 10. When uranium interacts with heavier nuclei the features of the reaction change drastically: while fission is the main mechanism for the production of light masses in 1 A GeV 238 U on H 2 , projectile fragmentation plays a dominant role in 1 A GeV 238 U on Ti leading to the formation of stable or neutron-deficient isotopes of all elements.

A new approach to describing neutron spectra of deuteron-induced reactions in the Monte Carlo simulation for particle transport has been developed by combining the Intra-Nuclear Cascade of Liege (INCL) and the Distorted Wave Born Approximation (DWBA) calculation. We incorporated this combined method into the Particle and Heavy Ion Transport code System (PHITS) and applied it to estimate ( d , xn ) spectra on nat Li, 9 Be, and nat C targets at incident energies ranging from 10 to 40 MeV. Double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively, at the same energies as those observed in experimental data. Furthermore, an excellent agreement was observed between experimental data and PHITS-derived results using the combined method in thick target neutron yields over a wide range of neutron emission angles in the reactions. We also applied the new method to estimate ( d , xp ) spectra in the reactions, and discussed the validity for the proton emission spectra.

It is well known that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one-nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons of this deficiency. We find that a correct description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables. Neither ingredient is sufficient if taken separately., Presented at the 11th International Spring Seminar on Nuclear Physics. To be published in Journal of Physics: Conference Series

The purpose of this paper is twofold. First, we present the extension of the Li\`ege Intranuclear Cascade model to reactions induced by light ions. Second, we describe the C++ version of the code, which it is physics-wise equivalent to the legacy version, is available in Geant4 and will serve as the basis for all future development of the model. We describe the ideas upon which we built our treatment of nucleus-nucleus reactions and we compare the model predictions against a vast set of heterogeneous experimental data. In spite of the discussed limitations of the intranuclear-cascade scheme, we find that our model yields valid predictions for a number of observables and positions itself as one of the most attractive alternatives available to Geant4 users for the simulation of light-ion-induced reactions., Comment: Submitted to Phys. Rev. C

The production of primary residual nuclei in the reaction 1 A GeV 208Pb on proton has been studied by measuring isotopic distributions for all elements from titanium (Z=22) to lead (Z=82). Kinematical properties of the residues were also determined and used to disentangle the relevant reaction mechanisms, spallation (projectile fragmentation) and fission. The fragment separator FRS at GSI, Darmstadt, was used to separate and identify the reaction products. The measured production cross sections are highly relevant for the design of accelerator-driven subcritical reactors and for the planning of future radioactive-beam facilities.

Experiments performed at Lab. Nat. SATURNE on neutron produced by spallation from proton beams in the range 0.8 - 1.6 GeV are presented. Experimental data compared with codes show a significant improvement of the recent intra-nuclear cascade (J. Cugnon). This is also true in the same way for the neutron production from thick targets. However the model underestimates the energetic neutrons produced in the backward direction and other quantities as residual nuclei cross sections are not accurately predicted.

Fission induced by 197 Au on proton collisions is investigated in order to study the nuclear viscosity in highly excited nuclear matter. The isotopic identification of the fission residues allows to determine the mean values of the mass number, nuclear charge and excitation energy of the fissioning nuclei at saddle. The comparison of these properties with statistical fission calculations evidences the role of the nuclear viscosity in the description of the fission dynamics.

Some improvements of the Intra-Nuclear Cascade code INCL4 for low energy projectiles are presented and discussed.

We have studied the deuteron breakup in the p(d,2p)n reaction at T{sub d}=2.0 GeV. In this experiment, the vector analyzing power A{sub Y}, the tensor analyzing power A{sub YY}, and the polarization of the forward scattered proton are measured close to the quasifree pp scattering kinematics. These observables are presented as a function of the neutron momentum ranging from 0.04 to 0.45 GeV/c in the rest frame of the deuteron. Marked deviations from the impulse approximation using conventional deuteron wave functions are observed. Corrections due to the multiple scattering, the final state interaction, and the {Delta} excitation are calculated in a model where the spin-isospin structure of the elementary amplitudes is treated rigorously. With this model, a reasonable account of the measured polarization observables is obtained. The global agreement with all observables is, however, not good enough that we can reliably discriminate between conventional wave functions. {copyright} {ital 1997} {ital The American Physical Society}

We present the experimental method conceived to measure high energy neutrons in the range (200 ≤ E ≤ 1600 MeV). The neutrons produce recoil protons in a liquid hydrogen converter. Momentum evaluation and identification of these protons are made by using a magnetic spectrometer equipped with plastic scintillators and three double-plane ( X - Y ) wire chambers. The response functions of the apparatus are determined using quasi-monoenergetic neutron beams produced by the break-up of deuterons or 3 He on a Be target. The performance of the apparatus is illustrated in the form of a preliminary neutron spectrum.

We present an experimental method based on a time-of-flight technique between the tagged incident particles and a thick liquid NE213 scintillator to measure neutron energy spectra from 3 to 400 MeV at the Saturne synchrotron of Saclay. Efficiency measurements are made using a pulsed neutron source from the Tandem Van de Graaff of Bruyeres-le-Châtel at low energies and a quasi-monoenergetic neutron beam at Saturne up to 50 MeV.