Generalized Evaporation Model Research Articles

Measurement of thick target neutron yield from 80.5 MeV/u 12C incidence on Be, C, W, and Pb targets

Thick target neutron yield produced from 80.5 MeV/u 12C ions stopping in the thick Be, C, W, and Pb targets were measured at 0°, 37°, 60° using liquid scintillation detector and the time of flight method. The experimental data were compared with those calculations using the Liege IntraNuclear-Cascade (INCL) implemented in Geant4 and the JAERI Quantum Molecular Dynamics 2.0 (JQMD-2.0) model followed by the Generalized Evaporation Model (GEM) implemented in PHITS, and default model implemented in FLUKA. The results of the three simulation codes with different physics models are similar for beryllium and carbon targets and in good agreement with the experimental data. For tungsten and lead targets, the calculation results from PHITS and FLUKA successfully reproduced the neutron spectra. While the results from GEANT4 overestimate the experimental data above 50 MeV at 0° and significantly underestimated experimental data in the 15–60 MeV energy range at 0°, 37° and 60°. In general, the simulation results of PHITS with the JQMD-2.0 physical model are in good agreement with the experimental data for all targets.

Emissions of Hydrogen Isotopes from the Nuclear Muon Capture Reaction in natSi

The energy spectra of protons, deuterons and tritons produced by the nuclear muon capture reaction in natSi were measured at the M1 beam line of Muon Science Innovative Channel (MuSIC) in Research Center for Nuclear Physics (RCNP) using a counter telescope consisting of a Si detector and a CsI(Tl) scintillation detector. The measured energy spectra were consistent with the previous ones. The experimental energy spectra were compared with theoretical model calculations using the Particle and Heavy Ion Transport code System (PHITS). In PHITS, both the dynamical and statistical processes in the nuclear muon capture reaction are described by the Quantum Molecular Dynamics (QMD) or the modified QMD and the Generalized Evaporation Model (GEM), respectively. The PHITS simulation reproduced generally well the measured proton spectrum at emission energies below 20 MeV, while underestimation was seen at emission energies above 20 MeV. The PHITS simulation underestimates remarkably the measured energy spectra of light complex particles (deuterons, tritons, and alpha particles) in the high energy region.

Measurement of thick target neutron yield at 180°for a mercury target induced by 3-GeV protons

A thick target neutron yield (TTNY) for a mercury target at an angle of 180°from the incident beam direction was measured with the time-of-flight method using a 3-GeV proton beam at the Japan Proton Accelerator Research Complex (J-PARC). Comparison of the experimental results with a Monte Carlo particle transport simulation by the Particle and Heavy Ion Transport code System (PHITS) shows that the default spallation model of PHITS, the Liège intranuclear cascade model version 4.6 coupled with the generalized evaporation model (INCL4.6/GEM) reproduces the measured TTNY fairly well, whereas apparent overestimation is observed for the former default model, the Bertini intranuclear cascade model coupled with GEM (Bertini/GEM). These trends are consistent with the experimental results of neutron-induced reaction rates obtained using indium and niobium activation foils.

Development of INC-ELF version 2 and incorporation into PHITS: Extension to lower incident energies down to 30 MeV

Version 2 of the Intranuclear Cascade with Emission of Light Fragments (INC-ELF) code is developed and incorporated into the Particle and Heavy Ion Transport code System (PHITS). The aim of INC-ELF2 is to expand it to the lower incident-energy range of 30–200 MeV, where the original INC theory is not applicable. The refinement of the code is based faithfully on the results of basic research on direct reactions within the framework of the INC model. INC-ELF2 can deal with the emission of light fragments from nuclear reactions induced by protons and neutrons. Double-differential cross-sections are calculated by a two-step model combining INC-ELF2 and GEM (generalized evaporation model) in PHITS, and they are compared with experimental data to examine the predictive ability. Excellent agreement is confirmed for various reactions over a wide range of target masses and over the incident-energy range of 30–200 MeV.

Measurement of thick target neutron yields from 7 MeV/u [formula omitted] incidence on 209Bi

Thick target neutron yields produced by 7 MeV/u α incidence on a 209Bi target were measured at emission angles of 0°, 45°, and 90° using EJ301 liquid scintillators and the time-of-flight method. The experimental thick target yields were compared with those calculated using the Liège IntraNuclear-Cascade (INCL) and the JAERI Quantum Molecular Dynamics (JQMD) models followed by the Generalized Evaporation Model (GEM) implemented in PHITS. The INCL model successfully reproduced the neutron energy distribution. In contrast, the JQMD model could not reproduce the distribution, even for the reactions induced by low energy composite particles.

Neutron production from thick LiF, C, Si, Ni, Mo, and Ta targets bombarded by 13.4-MeV deuterons

Double-differential thick target neutron yields from LiF, C, Si, Ni, Mo, and Ta targets bombarded by 13.4-MeV deuterons were measured by using an EJ-301 liquid organic scintillator at the Center for Accelerator and Beam Applied Science, Kyushu University. The measured (d, xn) spectra were compared with the (t, xn) spectra measured by the other group at the same incident energy per nucleon (6.7 MeV/u) and theoretical model calculations by Particle and Heavy Ion Transport code System (PHITS) and DEUteron-induced Reaction Analysis Code System (DEURACS). Some bumps are observed in the (d, xn) spectra for low-Z target elements, while no specific structure was seen in the (t, xn) spectra. The PHITS calculation, in which the intra-nuclear cascade of Liége (INCL) and generalized evaporation model (GEM) were used, generally overestimates neutron spectra while the DEURACS calculation agrees with experimental ones fairly well.

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.

A Generalized Evaporation Model for Chinese Pans

AbstractPan evaporation (Epan) measurements are used for gauging the atmospheric evaporative demand, and Epan observation networks were established and maintained for a long history. However, due to the replacement of D20 pans with 601B pans across China in 2000, Epan observation networks in China, which is the largest networks in East Asia, became discontinuous. Thus, it is important to develop a robust method to update and complement Epan of two Chinese pans. PenPan model is a robust model in Epan estimation, while the previous versions of PenPan are derived for a specific type of pan. This study developed a generalized model, that is, PenPan‐V3 model, to simulate Epan for Chinese pans. The PenPan‐V3 model simulated the irradiance of each part of pans; that is, pan water surface, pan rim, side wall and pan bottom, and the simulated Epan coincided with the observations of D20 and 601B pans. For D20 pans, aerodynamic component (Epan,A) and radiative component (Epan,R) of Epan were 60% and 40%, respectively. The contributions of pan water surface, inside and outside pan rim, side wall, and pan bottom to Epan,R were 23%, 38%, 26%, 6%, and 7%, respectively. For 601B pans, Epan,A and Epan,R were 42% and 58% of Epan, respectively. The contributions of pan water surface and inside and outside pan rim to Epan,R were 94%, 5% and 1%, respectively. The PenPan‐V3 model benefits establishing the long‐term continuous Epan networks in China, which can be used for evaluating the long‐term trends of atmospheric evaporative demand in East Asia.

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.

An intranuclear cascade model for inelastic scattering and breakup reactions involving deuterons and alpha particles

ABSTRACT The intranuclear cascade model is extended to cluster-induced (deuteron and alpha particle) nuclear reactions involving inelastic scattering and breakup reactions. The proposed model explains the projectile breakup process by describing the projectile cluster as a superposition of several states. The incident cluster and the produced cluster are assumed to be collections of independent particles and may undergo nuclear interaction through nucleon–nucleon interaction with the target nucleus. Trajectory deflections for the projectile and ejecta are incorporated in the model to account for angular distributions. Calculations with the proposed model followed by the generalized evaporation model are performed for validation by comparing with experimental double-differential cross-section spectra produced by bombarding an 27Al target separately with 80-MeV and 99.6-MeV deuterons and 140-MeV alpha particles. The calculation results show good agreement with experimental spectra.

Systematic measurement of double-differential neutron production cross sections for deuteron-induced reactions at an incident energy of 102 MeV

Double-differential neutron production cross sections (DDXs) for deuteron-induced reactions on Li, Be, C, Al, Cu, and Nb at 102MeV were measured at forward angles ≤25° by means of a time of flight (TOF) method with NE213 liquid organic scintillators at the Research Center of Nuclear Physics (RCNP), Osaka University. The experimental DDXs and energy-integrated cross sections were compared with TENDL-2015 data and Particle and Heavy Ion Transport code System (PHITS) calculation using a combination of the KUROTAMA model, the Liege Intra-Nuclear Cascade model, and the generalized evaporation model. The PHITS calculation showed better agreement with the experimental results than TENDL-2015 for all target nuclei, although the shape of the broad peak around 50MeV was not satisfactorily reproduced by the PHITS calculation.

Angular distribution of evaporated protons from 50-MeV-range proton-nucleus reactions

The angular distribution of compound reactions at bombarding energies lower than 10 MeV is known to be 90˚ symmetry. At the higher incident energies, 50-MeV range, the quantization axis tilts from the beam axis due to the particle emission in the cascade or the pre- equilibrium process. Therefore, it is necessary to know the tilted quantization axis for the angular distribution calculation of the evaporated protons from (p, p'x) reactions. In the present work, we applied the intranuclear cascade (INC) model to determine the tilted quantization axis by a classical vector analysis. The proton evaporation was calculated by the generalized evaporation model (GEM). By fitting calculations to experimental angular distributions, we deduced the angular momentum transfer from the equilibrium state.

Intranuclear cascade model for 50-MeV-region (p, p′x) reactions over a wide target mass range

In our previous study, the applicable range of the intranuclear cascade model was successfully extended to lower incident energy (p, p′x) reactions by introducing trajectory deflections and low-energy-loss process due to collective excitations. However, the model's validity was confirmed only for a 56Fe target. In the present work we widen the applicable range of masses of the target nucleus. First, we derive an expression for the response function, which gives the probability of collective excitation strengths, to fit the distorted-wave Born approximation results as a function of the target mass number and the beam energy. Second, the barrier transmission coefficient was investigated. An expression with a modified Gamow penetration factor was chosen from four phenomenological forms of one-dimensional barrier transmission coefficients. Calculations with the proposed model followed by a generalized evaporation model were carried out for double-differential cross sections of (p, p′x) reactions at 30–60 MeV. Although the response function and the transmission coefficient were only parameterized approximately, the proposed model showed good agreements with experimental observations for a variety of nuclear targets from 12C to 209Bi.

Benchmarking geant4 nuclear models for hadron therapy with 95 MeV/nucleon carbon ions

In carbon-therapy, the interaction of the incoming beam with human tissues may lead to the production of a large amount of nuclear fragments and secondary light particles. An accurate estimation of the biological dose deposited into the tumor and the surrounding healthy tissues thus requires sophisticated simulation tools based on nuclear reaction models. The validity of such models requires intensive comparisons with as many sets of experimental data as possible. Up to now, a rather limited set of double di erential carbon fragmentation cross sections have been measured in the energy range used in hadrontherapy (up to 400 MeV/A). However, new data have been recently obtained at intermediate energy (95 MeV/A). The aim of this work is to compare the reaction models embedded in the GEANT4 Monte Carlo toolkit with these new data. The strengths and weaknesses of each tested model, i.e. G4BinaryLightIonReaction, G4QMDReaction and INCL++, coupled to two di fferent de-excitation models, i.e. the generalized evaporation model and the Fermi break-up are discussed.

Differential cross sections on fragment (2 ≤ Z ≤ 9) production for carbon, aluminum and silicon induced by tens-of-MeV protons

The double-differential cross sections (DDXs) for the inclusive reactions producing heavy nuclei with Z = 2–9 (fragments) from carbon, aluminum, and silicon targets induced by 50 and 70 MeV protons are systematically measured at several angles (30°, 60°, 90°, and 135°) using a specially developed Bragg curve counter and the energy-time-of-flight method. The DDXs of a silicon target for the proton-induced reaction producing fragments heavier than lithium were measured for the first time. The present results are compared with past experimental data, the LA150 evaluated data by the Los Alamos group and several intranuclear cascade models (Bertini and ISOBAR), and the JAEA-version quantum molecular dynamics model (JQMD) coupled with the Generalized Evaporation Model (GEM), which are implemented in the Particle and Heavy Ion Transport code System (PHITS). The present results agree well with the past experimental data and LA150 data for α -particle production. For the fragments heavier than lithium, the present results show forward-peak angular distributions rather than isotropic ones stored in LA150. Calculations with the ISOBAR and GEM models well reproduced our experimental results except for light fragments especially in the high-energy region.

ESTIMATING NEUTRON DOSE EQUIVALENT RATES FROM HEAVY ION REACTIONS AROUND 10 MeV amu−1 USING THE PHITS CODE

It has been sometimes necessary for personnel to work in areas where low-energy heavy ions interact with targets or with beam transport equipment and thereby produce significant levels of radiation. Methods to predict doses and to assist shielding design are desirable. The Particle and Heavy Ion Transport code System (PHITS) has been typically used to predict radiation levels around high-energy (above 100 MeV amu(-1)) heavy ion accelerator facilities. However, predictions by PHITS of radiation levels around low-energy (around 10 MeV amu(-1)) heavy ion facilities to our knowledge have not yet been investigated. The influence of the "switching time" in PHITS calculations of low-energy heavy ion reactions, defined as the time when the JAERI Quantum Molecular Dynamics model (JQMD) calculation stops and the Generalized Evaporation Model (GEM) calculation begins, was studied using neutron energy spectra from 6.25 MeV amu(-1) and 10 MeV amu(-1) (12)C ions and 10 MeV amu(-1) (16)O ions incident on a copper target. Using a value of 100 fm c(-1) for the switching time, calculated neutron energy spectra obtained agree well with the experimental data. PHITS was then used with the switching time of 100 fm c(-1) to simulate an experimental study by Ohnesorge et al. by calculating neutron dose equivalent rates produced by 3 MeV amu(-1) to 16 MeV amu(-1) (12)C, (14)N, (16)O, and (20)Ne beams incident on iron, nickel and copper targets. The calculated neutron dose equivalent rates agree very well with the data and follow a general pattern which appears to be insensitive to the heavy ion species but is sensitive to the target material.

A study of proton-induced spallation reactions by the improved quantum molecular dynamics model plus statistical decay models

The recent GSI data for proton-induced spallation reactions by using inverse kinematics are analyzed by the improved quantum molecular dynamics model (ImQMD05) merged with the generalized evaporation model (GEM2) and GEMINI model. We find that the model of ImQMD05+GEM2 reproduces the experimental data of mass and charge distributions for proton-induced spallation reactions on heavy targets (208Pb, 238U and 197Au) well and the model of ImQMD05+GEMINI reproduces the ones on light targets (56Fe) well. The experimental data for double differential cross sections of emitted neutrons and protons in intermediate energy proton-induced spallation reactions can also be reproduced well with the same models and this shows that they are not very sensitive to the merged statistical model.

Validation of JENDL High-Energy File through Analyses of Spallation Experiments at Incident Proton Energies from 0.5 to 2.83 GeV

The most updated version of the JENDL high-energy file, JENDL/HE-2007, was validated with a focus on heavy elements of W, Pb, and Hg through analyses of spallation experiments using thick targets at incident proton energies from 0.5 to 2.83 GeV. For this purpose, the processing of the PHITS code system was adjusted to simulate nucleon transport phenomena using only a cross-section library including pionproduction data up to 3 GeV with the aid of an intranuclear cascade evaporation model to treat reactions induced by accompanied pions. It was found that the data up to 3 GeV in JENDL/HE-2007 predict the neutron spectra produced in thick targets with energies lower than 15MeV with good accuracy while they underestimate those from 20 to 100MeV by a factor of 0.4 to 0.5. It is also confirmed from analyses of the reaction rates in thick targets that the cross-section data of the dosimetry reactions of 93Nb(n,4n)90Nb and 59Co(n,4n)56Co for high-energy neutron field are reasonable. The present benchmark is the first index that JENDL/HE-2007 is applicable to neutronic design for a spallation-based facility with almost the same accuracy as for a conventional methodology using the intranuclear cascade model of Bertini and generalized evaporation model (GEM).

Quantum molecular dynamics calculation of light-ion production in neutron-induced reactions at intermediate energies

A quantum molecular dynamics (QMD) simulation is applied to light-ion production in neutron-induced reactions on O, Si and Fe at E(n) = 96 MeV. The generalized evaporation model (GEM) is used to account for statistical decay processes after the QMD stage. Good agreement with the experimental energy spectra is obtained for proton emission, but the calculation exhibits remarkable underestimation for pre-equilibrium emission of light clusters, i.e. d, t, (3)He and (4)He. It is found that the underestimation is improved except in the region around the high energy end of the emission spectra by implementation of a phenomenological coalescence model into the QMD under the assumption that these light clusters are formed in the nuclear surface region by a leading nucleon that is ready to leave the nucleus.

Development of a quantum molecular dynamic (QMD) model to describe fission and fragment production

QMD model coupled with Generalized Evaporation model by S. Furihata (GEM2) is applied for a description of fission nuclei production in p+U interactions at 100 MeV, and for a description of p+Pb --> Bi+X reactions at 10-200 MeV. A good reproduction of the data has been reached.