Intranuclear Cascade Research Articles

Intra-Nuclear Cascade (INC) code for simulation of meson photoproduction in nuclei

η meson photoproduction in the 14N nucleus was studied using simulations done with INC (Intra-Nuclear Cascade) code. The probability for mesons and nucleons to escape the nucleus on different steps of the reaction was evaluated. These results predict the possibility of studying elastic and inelastic η meson interactions with intra-nuclear nucleons using the recoil proton as a tag for the case of slow η meson and fast recoil proton.

Improvements of INCL4 in view of more reliable predictions for RIB facilities

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

Calculation and evaluation of cross-sections for p+54,56,57,58,natFe reactions up to 250 MeV

All cross-sections of proton-induced reactions, angular distributions and the energy spectra of neutron, proton, deuteron, triton, helium and alpha-particle emission are consistent calculated and analyzed for p+54,56,57,58,natFe at incident proton energies below 250MeV by using nuclear theoretical models which integrate the optical model, the intra-nuclear cascade model, direct, preequilibrium and equilibrium reaction theories. Especially, the cross-sections of the light composite particle (d, t, 3He and α) emissions are improved based on the exciton model including the pick-up mechanism. Theoretical calculated results are compared with existing experimental data.

The quenching of nucleon yields in the nonmesonic weak decay of Λ -hypernuclei and the three-body weak decay process

Recent exclusive coincidence measurements of non-mesonic weak decays (NMWD) reported for the ratio of the partial decay width of neutron-induced-to-proton-induced NMWD, Γ n/Γ p , values of 0.45±0.11±0.03 and 0.51±0.13±0.04 for Λ 5 He and Λ 12 C, respectively. These observations agree well with the improved theoretical Γ n /Γ p ratios which are in the range of 0.3–0.7. It appears that the long-standing discrepancy between the experimental and theoretical values of Γ n /Γ p has finally been solved. However, when compared to the results of intra-nuclear cascade (INC) calculations, the observed numbers of both single nucleons and coincident nucleon pairs are strongly quenched. The quenching of the proton yield observed previously has been interpreted as an increase of the Γ n /Γ p ratio. On the other hand, significant contributions from the two-nucleon-induced three-body process ΛNN → nNN are predicted. Indeed, the angular correlation of the emitted nucleon pairs in the NMWD of Λ 12 C showed not only decay events in back-to-back kinematics, but also events with non-back-to-back kinematics. In this paper we show that the difficulties to extract the correct Γ n /Γ p ratio from the proton spectra is related to the three-body weak-interaction process which strongly quenches the nucleon yields.

Non-equilibrium emission of complex fragments fromp+Aucollisions at 2.5 GeV proton beam energy

The energy and angular dependence of double differential cross sections d 2 σ/ ddE was measured for reactions induced by 2.5 GeV protons on Au target with isotopic identification of light products (H, He, Li, Be, and B) and with elemental identification of heavier intermediate mass fragments (C, N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction mechanisms give comparable contributions to the cross sections. The intranuclear cascade of nucleon-nucleon collisions followed by evaporation from an equilibrated residuum describes the low energy part of the energy distributions whereas another reaction mechanism is responsible for the high energy part of the spectra of composite particles. A phenomenological model description of the differential cross sections by isotropic emission from two moving sources led to a very good description of all measured data. Values of the extracted parameters of the emitting sources are compatible with the hypothesis claiming that high energy particles emerge from preequilibrium processes consisting in a breakup of the target into three groups of nucleons; small, fast, and hot fireball of ∼8 nucleons, and two larger, excited prefragments, which emit light charged particles and intermediate mass fragments. The smaller of them contains ∼20 nucleons and moves with a velocity larger than the CM velocity of the proton projectile and the target. The heavier prefragment behaves similarly as the heavy residuum of the intranuclear cascade of nucleon-nucleon collisions.

Inclusive pion double charge exchange in lightp-shell nuclei

We report the results of a series of measurements of the differential cross sections for inclusive pion double charge exchange in $^{6,7}\mathrm{Li}$, $^{9}\mathrm{Be}$, and $^{12}\mathrm{C}$ for positive and negative incident pions of energies 120, 180, and 240 MeV. The data are compared with the predictions of an intranuclear cascade model and a model based on two sequential single charge exchange processes.

Non-equilibrium nucleon spectra from reactions at intermediate energies

A new exciton model of pre-equilibrium decay (Monte Carlo Pre-equilibrium) to compute spectra of multiparticle emission during an establishment of statistical equilibrium in the composite system is proposed. The MCP stage of the calculation was included into the standard scheme of the nucleon spectra calculation between the intranuclear cascade stage and statistical model stage. A systematic comparison of calculation results with experimental spectra of nucleons from (p,xn), (p,xp), (n,xn) and (n,xp) reactions in a wide projectile energy region from 10 up to 160 MeV for targets from (27)Al up to (209)Bi has been carried out. A short description of the MCP model and results obtained are presented.

Spallation residues in the reactionFe56+pat0.3A,0.5A,0.75A,1.0A, and1.5AGeV

The spallation residues produced in the bombardment of Fe56 at 1.5A,1.0A,0.75A,0.5A, and 0.3A GeV on a liquid-hydrogen target have been measured using the reverse kinematics technique and the fragment separator at GSI (Darmstadt). This technique has permitted the full identification in charge and mass of all isotopes produced with cross sections larger than 10−2 mb down to Z=8. Their individual production cross sections and recoil velocities at the five energies are presented. Production cross sections are compared with previously existing data and with empirical parametric formulas, often used in cosmic-ray astrophysics. The experimental data are also extensively compared with the results of different combinations of intranuclear cascade and deexcitation models. It is shown that the yields of the lightest isotopes cannot be accounted for by standard evaporation models. The GEMINI model, which includes an asymmetric fission decay mode, gives an overall good agreement with the data. These experimental data can be directly used for the estimation of composition modifications and damages in materials containing iron in spallation sources. They are also useful for improving high-precision cosmic-ray measurements.23 MoreReceived 24 October 2006DOI:https://doi.org/10.1103/PhysRevC.75.044603©2007 American Physical Society

Particle production in nucleon induced reactions above 14 MeV with an intranuclear cascade model

We present an intranuclear cascade (INC) model which includes the dynamics of the cascade particles and uses in-medium $\mathit{NN}$ elastic cross sections. Our model is still based on the impulse approximation and does not have the complexity of other sophisticated nuclear models. Nevertheless, its results of angle-energy distributions of emitted nucleons in continuum are in good agreement with experimental data for nucleon induced reactions from low intermediate energy to high energy, between 14 MeV and 1.6 GeV, and for light to heavy target nuclei. Comparisons with results of Bertini's INC model and of a previous version of our INC model show the clear contribution of the combined effects of better dynamics and the in-medium $\mathit{NN}$ cross sections. From our results, we conclude that our INC model effectively includes the preequilibrium emission.

Photon-induced multiple particle emissions ofZr90andnatZr from 10 to 140 MeV

A comprehensive analysis of electrodisintegration yields of protons on {sup 90}Zr is proposed taking into account the giant dipole resonance, isovector giant quadrupole resonance (IVGQR), and quasideuteron contributions to the total photoabsorption cross section from 10 to 140 MeV. The calculation applies the MCMC intranuclear cascade to address the direct and pre-equilibrium emissions and another Monte Carlo-based algorithm to describe the evaporation step. The final results of the total photoabsorption cross section for {sup 90}Zr and relevant decay channels are obtained by fitting the (e,p) measurements from the National Bureau of Standards and show that multiple proton emissions dominate the photonuclear reactions at higher energies. These results provide a consistent explanation for the exotic and steady increase of the (e,p) yield and also a strong evidence of a IVGQR with a strength parameter compatible with the E2 energy-weighted sum rule. The inclusive photoneutron cross sections for {sup 90}Zr and {sup nat}Zr, derived from these results and normalized with the (e,p) data, are in agreement within 10% with both Livermore and Saclay data up to 140 MeV.

The INCL model for spallation reactions below 10 GeV

The Liège intranuclear cascade (INCL) model is shortly presented. The predictive power of its standard version concerning the description of nucleon-induced spallation reactions in the 200 MeV to 2 GeV range of incident energy is indicated. Current improvements of the model, in particular its extension to higher energies, are emphasized. The capabilities of the model for possible applications in astrophysics, space research and protontherapy are pointed out.

FRAGMENTATION PRODUCTION CROSS-SECTIONS IN RELATIVISTIC COLLISIONS

In this study, the fragmentation production cross-sections of heavy residual nuclides in the reactions 238 U (1 A GeV ) + p and p (1.2 GeV ) + 232 Th were calculated and the production of more than 370 different isotopes for this incident reactions was presented. The calculations were made by using the Cascade-Exciton Model including pre-equilibrium effect, the Intranuclear Cascade Model, the empirical and the semi-empirical parametrization. The results of the cross-sections obtained were compared with available experimental data and examined the relation between each other. It is seen that the precision of this models to estimate residue production cross-sections is still far from the performance required for technical applications and this incident model should be improved to obtain a deeper understanding of the reaction mechanisms involved in the production of isotopes.

Pion physics in the Liège intranuclear cascade model

The implementation of \ensuremath{\pi} production in the Li\`ege intranuclear cascade model (INCL4) for spallation reactions is revisited to alleviate the overestimate of the \ensuremath{\pi} yield. Three modifications are proposed for this purpose: a better $\ensuremath{\pi}N$ cross section at high energy, the introduction of a \ensuremath{\pi} average potential, and the modification of the average mass of the \ensuremath{\Delta} resonance. The \ensuremath{\pi} potential is determined from a global fit of a set of data bearing on \ensuremath{\pi} production in proton-induced reactions, on $\ensuremath{\pi}$-nucleus and absorption cross sections, and on proton production in \ensuremath{\pi}-induced reactions. The resulting \ensuremath{\pi} potential is poorly determined in the nuclear interior and agrees with the phenomenological optical-model potentials in the surface region. With these modifications, the predictions of the INCL4 model concerning \ensuremath{\pi} production cross sections in proton-induced reactions are considerably improved. Predictions of the improved version for $\ensuremath{\pi}$-nucleus reaction and absorption cross sections and for proton, residue, and fission cross sections in \ensuremath{\pi}-induced reactions are also presented and shown to give reasonably good agreement. Neutron production and some aspects of fission in \ensuremath{\pi}-induced reactions are also investigated and reasonably well predicted. Effects on the modifications on observables, which are not directly linked with \ensuremath{\pi}'s, such as the neutron yield and the residue mass and charge spectra in proton-induced reactions are also investigated and shown to improve the description of these observable quantities. Several results on \ensuremath{\pi} production and the relative insentivity to the \ensuremath{\pi} potential in the nuclear interior are shown to be consistent with the fact that most \ensuremath{\pi}'s are not produced in early collisions. Importance of rescattering in \ensuremath{\pi} absorption on nuclei is also pointed out. A comparison is made with the so-called \ensuremath{\Delta}-hole model. Residual discrepancies are identified and are interpreted as due to the lack of \ensuremath{\pi} interaction with two nucleons at low energy, to the neglect of quantum motion effects, and to a possible underestimate of rescattering.

The nuclear matter effects in pi0 photoproduction at high energies

The in-medium influence on p0 photoproduction from spin zero nuclei is carefully studied in the GeV range using a straightforward Monte Carlo analysis. The calculation takes into account the relativistic nuclear recoil for coherent mechanisms (electromagnetic and nuclear amplitudes) plus a time dependent multi-collisional intranuclear cascade approach (MCMC) to describe the transport properties of mesons produced in the surroundings of the nucleon. A detailed analysis of the meson energy spectra for the photoproduction on 12C at 5.5 GeV indicates that both the Coulomb and nuclear coherent events are associated with a small energy transfer to the nucleus ($\lesssim$ 5 MeV), while the contribution of the nuclear incoherent mechanism is vanishing small within this kinematical range. The angular distributions are dominated by the Primakoff peak at extreme forward angles, with the nuclear incoherent process being the most important contribution above $\theta_{\pi^{0}}\gtrsim2^{0}$. Such consistent Monte Carlo approach provides a suitable method to clean up nuclear backgrounds in some recent high precision experiments, such as the PrimEx experiment at the Jefferson Laboratory Facility.

Isotopic production cross sections of spallation-evaporation residues from reactions ofU238(1AGeV) with deuterium

Isotopic production cross sections and momentum distributions of 602 residual nuclei produced in the collision of $^{238}\mathrm{U}$($1A$ GeV) with deuterium have been measured. These data are relevant for a better understanding of spallation reactions for use as neutron sources for accelerator-driven systems or to produce radioactive nuclear beams. Access to primary residue production makes it possible to study the main reaction mechanisms involved: intranuclear cascade, particle evaporation, and fission. The characteristics of the reaction investigated and the high fissility of the $^{238}\mathrm{U}$ and the dinucleon projectile system are discussed and compared with other available experimental data.

The NCSU radiation damage database; proton-induced damage energy and application to radiation damage at SINQ

The NCSU radiation damage database is described. It contains proton and neutron cross sections for production of damage energy, displacements, helium, hydrogen, and heavier transmutation products. The targets in the database include 23 elements from Mg to U and eight practical alloys, but for this paper attention is focused on Al, Fe, and W. Damage energy cross sections are presented for 20–3200-MeV protons based on intranuclear cascade (INC) models (Bertini, CEM2k, and ISABEL) and for 1–2000-MeV protons based on classical Rutherford scattering and SRIM. These cross sections are used to calculate displacement production at SINQ Target 5. It is shown that the SRIM-calculated cross sections can make a significant contribution to proton-induced displacement production in Al at the entrance window and in Fe at Rods 1 and 15.

Spallation Radiation Damage Calculations and Database: Cross-Section Discrepancies between the Codes

Abstract A radiation damage database at NCSU is described that contains, at present, cross sections for damage energy, displacements, helium, and hydrogen. For neutrons and protons at 20-3200 MeV energies, the targets include 23 target elements from Mg to U and eight practical alloys. The underlying calculations employ Bertini, ISABEL, and CEM2k intranuclear cascade models as provided within MCNPX, three level-density formulations (GCCI, HETC, and Jülich), and multistage pre-equilibrium model (MPM) on and off. The database also includes radiation damage cross sections for lower-energy neutrons and protons, as obtained from LA150, SPECTER, ENDF, and SRIM. Examples of the database contents are provided with regard to damage energy and displacement cross sections for neutrons on Al, Fe, and W. Also, neutron flux and displacement rate calculations are described for neutrons on Fe and the 316 stainless steel mercury container vessel at SNS. In addition, discrepancies between the codes are discussed.

Calculations of Proton-Induced Neutron Production Cross Sections on 232Th up to 1.6 GeV

The 232Th(p,xn) and 232Th(p,np) cross sections for incident proton energies in the range of 10 to 1600 MeV have been calculated by using a cascade-exiton model (CEM) combining essential features of the exciton model and intranuclear cascade models. The level density parameter effects are investigated. The calculation results are compared with the available measured data.

CEM03 and LAQGSM03—new modeling tools for nuclear applications

An improved version of the Cascade-Exciton Model (CEM) of nuclear reactions realized in the code CEM2k and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) have been developed recently at LANL to describe reactions induced by particles and nuclei for a number of applications. Our CEM2k and LAQGSM merged with the GEM2 evaporation/fission code by Furihata have predictive powers comparable to other modern codes and describe many reactions better than other codes; therefore both our codes can be used as reliable event generators in transport codes for applications. During the last year, we have made a significant improvements to the intranuclear cascade parts of CEM2k and LAQGSM, and have extended LAQGSM to describe photonuclear reactions at energies to 10 GeV and higher. We have produced in this way improved versions of our codes, CEM03.01 and LAQGSM03.01. For special studies, we have also merged our two codes with the GEMINI code by Charity and with the SMM code of Botvina. We present a brief description of our codes and show illustrative results obtained with CEM03.01 and LAQGSM03.01 for different reactions compared with predictions by other models, as well as examples of using our codes as modeling tools for nuclear applications.

Charged-particle evaporation and pre-equilibrium emission in 1.2 GeV proton-induced spallation reactions

Absolute cross sections, energy spectra, and angular distributions have been measured for 1,2,3H, 3,4,6He, 6,7,8,9Li and 7,9,10Be isotopes produced in 1.2 GeV proton-induced spallation reactions with targets between Al and Th. Results of simulation calculations with the intra-nuclear cascade code INCL2.0 coupled to the statistical model GEMINI are in good agreement with these data, as to charged-particle evaporation, mean excitation energy, and mean linear momentum transfer. The pre-equilibrium emission of composite particles, not accounted for in these simulations, however, typically contributes to the total production of composite particles by 40–60% for 2H and 3He, 20–40% for 3H, 5–20% for 4He, and about 15–25% for Li and Be. The composite pre-equilibrium particles together carry off a mean energy of up to 50 MeV, i.e., about 30% compared to the mean energy released by particle evaporation. For deuterons, pre-equilibrium emission is shown to be well described by surface coalescence while definitely other mechanisms are required for 4He and heavier clusters.