Neutron Production Cross Sections Research Articles

Built-in physics models and proton-induced nuclear data validation using MCNP, PHITS, and FLUKA – Impact on the shielding design for proton accelerator facilities

The MCNP, PHITS, and FLUKA are general-purpose Monte Carlo (MC) radiation transport codes that are widely used for many real-world shielding problems at accelerator facilities around the world. Nuclear interactions are described in these codes by either built-in physics models, or tables with evaluated cross sections and secondary energy-angular distributions, or a combination of both. Over the decades, many code validation efforts have been made, owing to the availability of shielding benchmarks to test the physics models and nuclear data and to verify the accuracy of simulation codes.For high beam energy and high beam current accelerator applications, neutron emission through the vacuum pipe along the reverse direction of incident proton beam is an important factor for a shielding design in order to correctly assess the dose rates for workers and the structural materials of the accelerator and handle with the waste activated by the backscattered neutron fluxes. In this work, neutron-production cross sections and thick-target yield predictions from MC codes relying on physics models and nuclear data libraries are benchmarked against the experimental data, in order to assess their accuracy in predicting neutron emission and furthermore to assess the corresponding impact on shielding design.The results of this study demonstrate that the nuclear data libraries and physics models, which are not expected to give good results at lower energies (< 150 MeV) but are used anyhow when there is no nuclear data available or above the energy range where the data tables end in the so-called “mix-and-match” strategy, need further improvements. Among the investigated proton induced nuclear data libraries, JENDL-4.0/HE produces the most satisfactory agreement to experimental data for all target materials, but may still benefit from refinement. Concerning the physics models of the codes, FLUKA V4-4.0 has the best performance in terms of reproducibility of the experimental values. It is also shown that all discrepancies between the calculations and the experiments for the energy range < 10 MeV (which is dominant on the dose rates through the shield thickness), are up to factor of two. This might be considered as an acceptable figure as it is equivalent to a normal safety margin (x2) considered in shielding calculations of accelerator facilities around the world.

Neutron-production double-differential cross sections of natPb and 209Bi in proton-induced reactions near 100 MeV

The lack of double-differential cross-section (DDX) data for neutron production below the incident proton energy of 200 MeV hinders the validation of spallation models in technical applications, such as research and development of accelerator-driven systems (ADSs). The present study aims to obtain experimental DDX data for ADS spallation target materials in this energy region and identify issues related to the spallation models by comparing them with the analytical predictions. The DDXs for the (p,xn) reactions of natPb and 209Bi in the 100-MeV region were measured over an angular range of 30° to 150° using the time-of-flight method. The measurements were conducted at Kyoto University utilizing the FFAG accelerator. The DDXs obtained were compared with calculation results from Monte Carlo-based spallation models (INCL4.6/GEM, Bertini/GEM, JQMD/GEM, ISOBAR/GEM, CEM03.03, INCL4/ABLA, Bertini/ABLA, ISABEL/ABLA, INCL++/ABLA07, INCL++/GEMINI++, and INCL++/SMM) and the evaluated nuclear data library, JENDL-5. Comparison between the measured DDX and analytical values based on the spallation models and evaluated nuclear data library indicated that, in general, the CEM03.03 model demonstrated the closest match to the experimental values. Additionally, the comparison highlighted several issues that need to be addressed in order to improve the reproducibility of the proton-induced neutron-production DDX in the 100 MeV region by these spallation models and evaluated nuclear data library. To enhance the reproducibility of underperforming spallation models and evaluated nuclear data library, it is recommended to address each of the issues identified in this study.

Deuteron and alpha sub-libraries of JENDL-5

JENDL-5, the latest version of the Japanese evaluated nuclear data library, includes several sub-libraries to contribute to various applications. In this paper, we outline the evaluation and validation of the deuteron reaction sub-library developed mainly for the design of accelerator-based neutron sources and the alpha-particle reaction sub-library developed mainly for use in the back-end field. As for the deuteron sub-library, the data for 6,7Li, 9Be, and 12,13C from JENDL/DEU-2020 were partially modified and adopted. The data up to 200 MeV for 27Al, 63,65Cu, and 93Nb, which are important as accelerator structural materials, were newly evaluated based on the calculations with the DEURACS code. As for the alpha-particle sub-library, the data up to 15 MeV for 18 light nuclides from Li to Si isotopes were evaluated based on the calculations with the CCONE code, and then only the neutron production cross sections were replaced with the data of JENDL/AN-2005. Validation on neutron yield by Monte Carlo transport simulations was performed for both sub-libraries. As a result, it was confirmed that the simulations based on the sub-libraries showed good agreement with experimental data.

From 232Th(n, n’γ) cross sections to level production and total neutron inelastic scattering cross sections

To probe the neutron inelastic scattering off 232Th, an experiment took place at the EC-JRC Geel conducted with the experimental setup GRAPhEME to detect emitted γ-rays. The prompt γ-ray spectroscopy method was used and 70 experimental 232Th(n, n’γ) cross sections were obtained from the experimental data. Combining these cross sections, nuclear-structure data available in databases and hypotheses to complete the latter, neutron inelastic level production cross sections in 232Th and the total inelastic cross section were calculated. For the first time, the total inelastic cross section of an actinide nucleus was derived on the total neutron energy range from experimental data only. Comparisons of (n, n’) cross section data with evaluated data reveal a good agreement between them all above 300 keV of neutron energy. TALYS calculations are compatible but lower than the evaluated data.

Cross section measurements of low-energy charged particle induced reactions using moderated neutron counter arrays

A high-and-flat efficiency moderated neutron detection array of 3He counters has been recently developed for photoneutron cross section measurements at the future ELI-NP gamma-ray beam source. We have designed a three rings geometry of 31 counters with a ˜37% efficiency flat within 5% in the 10 keV to 5 MeV neutron energy interval. A commissioning experiment was performed using proton beams delivered by the 9 MV Tandem accelerator of IFIN-HH. We measured the neutron production cross sections for proton induced reactions on nat Cu and 27Al. The (p, xn) reactions on nat Cu were investigated in the 4.5 MeV to 14 MeV proton energy range with 250 keV steps, using pulsed and continuous proton beams. The low energy measurements below 10 MeV served to validate the detection efficiency calibration against well-known natCu(p, n) cross sections. The 27Al(p, n) reaction was investigated in the 5.8 MeV to 6.75 MeV energy range with 5 keV steps. Preliminary cross section results are here compared with preceding data.

Neutron production in the interaction of 200-MeV deuterons with Li, Be, C, Al, Cu, Nb, In, Ta, and Au

Double-differential neutron production cross sections (DDXs) for 200-MeV deuteron induced reactions on Li, Be, C, Al, Cu, Nb, In, Ta, and Au were measured at forward emission angles ranging from 0° to 25° by means of a time of flight (TOF) method with EJ301 liquid organic scintillators. The measured DDXs were compared with JENDL-5 and TENDL-2021 nuclear data, and theoretical model calculations using DEURACS and PHITS codes. It was found that the JENDL-5 and DEURACS calculation are in better agreement with the measured DDXs than the PHITS calculation, while TENDL-2021 fails to reproduce both the spectral shape and magnitude of the measured DDXs for all the targets.

A new approach for simulating D-T fusion interaction using the Geant4 toolkit

In this study, the Geant4 toolkit is utilized to present a new approach for simulation of the D-T interaction. The neutron production cross-section and the energy/angle distribution of neutrons produced as the D-T data libraries are incorporated in the Geant4, and their performance is evaluated. The spectra shape of the produced neutrons of the D-T interaction simulated by the Geant4 show good agreement compared to the results of the comparative codes (i.e. MCUNED, ENEA-JSI, and DDT). However, some differences are observed, especially, in angular range of 90–95 degrees. The reason for these differences as well as the results of the proposed approach in comparison with the results of the benchmark experiments as the next study are under consideration.

Problems on neutron production data of Be-9 in TENDL-2017 and -2019 deuteron sub-libraries

We have identified several issues that neutron production data differed markedly among the official three kinds of 9Be ENDF-6 format files in the TENDL-2017: “the TENDF file”, “special ENDF file” and “another special ENDF file”. Our detailed investigation specified; (1) different neutron production cross section above 30 MeV in the “special ENDF file”, and (2) wrong secondary neutron energy distribution data in “the TENDF file” and/or “special ENDF file”. We confirmed that TENDL-2019, the latest version of TENDL, deleted the problematic “special ENDF file” and improved some of the wrong secondary neutron energy distribution data in “the TENDF file”. A simple test calculation indicated that “another special ENDF file” seemed to be physically the best among the three TENDL-2017 ENDF files. Analyses with thick target neutron yield experiments, however, demonstrated that even “another special ENDF file” did not reproduce the experimental data, while the test calculation using a new deuteron induced library from JENDL (JENDL/DEU-2020) showed good agreement with the experimental data.

Cross Sections for Neutron-Production from 6- and 10-MeV Neutrons Incident on 10B and 11B

Using time-of-flight techniques, we have measured neutron emission spectra from 6- and 10-MeV incident neutron energies on 10B and 11B for laboratory angles between 20 and 145 deg using the unique neutron source reaction 1H(t,n). Double-differential cross sections and their integrated values have been extracted for elastic and inelastic processes, and their integrated values are summarized. In cases where discrete scattering peaks could be analyzed, differential cross-section angular distributions have been extracted and are compared to other results and to evaluated nuclear data.

Double differential cross sections of neutron production by 135 and 180 MeV protons on A-150 tissue-equivalent plastic

The double differential cross sections (DDXs) of neutron production by 135 and 180 MeV protons were measured to obtain benchmark data for calculating neutron doses in proton therapy. The incident proton energies correspond to those of protons decelerating in a patient. An A-150 tissue-equivalent plastic was used as the target. The measured DDXs were compared with those calculated using PHITS, FLUKA, and Geant4. The calculated DDXs were found to be underestimated compared with the measured ones, especially at forward angles. In proton therapy, exposure evaluations using one of these simulation codes would underestimate the neutron dose.

Are Further Cross Section Measurements Necessary for Space Radiation Protection or Ion Therapy Applications? Helium Projectiles

The helium (4He) component of the primary particles in the galactic cosmic ray spectrum makes significant contributions to the total astronaut radiation exposure. 4He ions are also desirable for direct applications in ion therapy. They contribute smaller projectile fragmentation than carbon (12C) ions and smaller lateral beam spreading than protons. Space radiation protection and ion therapy applications need reliable nuclear reaction models and transport codes for energetic particles in matter. Neutrons and light ions (1H, 2H, 3H, 3He, and 4He) are the most important secondary particles produced in space radiation and ion therapy nuclear reactions; these particles penetrate deeply and make large contributions to dose equivalent. Since neutrons and light ions may scatter at large angles, double differential cross sections are required by transport codes that propagate radiation fields through radiation shielding and human tissue. This work will review the importance of 4He projectiles to space radiation and ion therapy, and outline the present status of neutron and light ion production cross section measurements and modeling, with recommendations for future needs.

Neutron production in ([formula omitted]) reactions

Neutrons can induce background events in underground experiments looking for rare processes. Neutrons in a MeV range are produced in radioactive decays via spontaneous fission and (α,n) reactions, and by cosmic rays. Neutron fluxes from radioactivity dominate at large depths (>1 km w. e.). A number of computer codes are available to calculate cross-sections of (α,n) reactions, excitation functions and neutron yields. We have used EMPIRE2.19/3.2.3 and TALYS1.9 to calculate neutron production cross-sections and branching ratios for transitions to the ground and excited states, and modified SOURCES4A to evaluate neutron yields and spectra in different materials relevant to high-sensitivity underground experiments. We report here a comparison of different models and codes with experimental data, to estimate the accuracy of these calculations.

Study of the Li(d, xn) reaction for the development of accelerator-based neutron sources

Double-differential neutron production cross sections (DDXs) for deuteron-induced reactions on Li at 200 MeV were measured for emission angles ranging from 0◦ to 25◦ in steps of 5◦ by means of a time of flight (TOF) method with EJ301 liquid organic scintillators at the Research Center for Nuclear Physics (RCNP), Osaka University. The measured DDXs were compared to theoretical model calculations with the DEURACS and PHITS codes and TENDL-2017 nuclear data. It was found that the DEURACS calculation is in better agreement with the measured DDXs than the PHITS calculation, while TENDL-2017 fails to reproduce both the spectral shape and magnitude of the measured DDXs for all angles.

7.2.2 Secondary Neutron Production Cross Section Measurements from Heavy-mass Targets at HIMAC

7.2.2 Secondary Neutron Production Cross Section Measurements from Heavy-mass Targets at HIMAC

Measurement of neutron-production double-differential cross sections of [formula omitted]C, 27Al, [formula omitted]Fe, and [formula omitted]Pb by 20, 34, 48, 63, and 78 MeV protons in the most-forward direction

In this study, the neutron-production double-differential cross sections (DDXs) of natC, 27Al, natFe, and natPb bombarded by 20, 34, 48, 63, and 78 MeV protons were measured in the most-forward direction by the time-of-flight (TOF) method using a liquid organic scintillator. Characteristic peak structures were observed in the measured neutron spectra, especially for light nuclei. The experimental data were compared with the results from the Monte Carlo simulation code “Particle and Heavy Ion Transport code System” (PHITS) using the theoretical model Liège Intranuclear Cascade (INCL) or using the Japanese evaluated nuclear data library (JENDL-4.0/HE). While the results of JENDL-4.0/HE were in agreement with the experimental data better than those of INCL, neither could reproduce the measured peak structures for some combinations of the beam and target. For the energy-integrated cross sections, JENDL-4.0/HE reproduced the experimental data within a factor of two in all cases. On the other hand, INCL gave values up to approximately six times larger than the experimental ones.

Measurement of inclusive forward neutron production cross section in proton-proton collisions at sqrt{s}=13 TeV with the LHCf Arm2 detector

In this paper, we report the measurement relative to the production of forward neutrons in proton-proton collisions at sqrt{s}=13 TeV obtained using the LHCf Arm2 detector at the Large Hadron Collider. The results for the inclusive differential production cross section are presented as a function of energy in three different pseudorapidity regions: η > 10.76, 8.99 < η < 9.22 and 8.81 < η < 8.99. The analysis was performed using a data set acquired in June 2015 that corresponds to an integrated luminosity of 0.194 nb−1. The measurements were compared with the predictions of several hadronic interaction models used to simulate air showers generated by Ultra High Energy Cosmic Rays. None of these generators showed good agreement with the data for all pseudorapidity intervals. For η > 10.76, no model is able to reproduce the observed peak structure at around 5 TeV and all models underestimate the total production cross section: among them, QGSJET II-04 shows the smallest deficit with respect to data for the whole energy range. For 8.99 < η < 9.22 and 8.81 < η < 8.99, the models having the best overall agreement with data are SIBYLL 2.3 and EPOS-LHC, respectively: in particular, in both regions SIBYLL 2.3 is able to reproduce the observed peak structure at around 1.5–2.5 TeV.

A function to provide neutron spectrum produced from the 9Be + p reaction with protons of energy below 12 MeV

ABSTRACTA function to give the total neutron production cross section, angular distribution, and energy spectrum via the 9Be + p reaction has been created by fitting experimental data to characterize compact neutron sources with thick Be targets bombarded by protons with energy below 12 MeV. To examine the suitability of the function, calculations of the angle-dependent neutron energy spectra produced in thick Be targets with 4- and 12-MeV protons using the function were compared with corresponding experiments and calculations using the nuclear data libraries of ENDF/B-VII.0 and JENDL4.0/HE. The function was in better agreement with the experiments than the calculations using the libraries except for at backward angles. The 115In(n,n’)115mIn reaction rates calculated using GEANT4 with source neutrons given by both the function and ENDF/B-VII.0 were compared with that measured at the RIKEN Accelerator-Driven Compact Neutron Source to evaluate the neutron spectrum above 1 MeV. The function slightly overestimated the measurement by 14% and the calculation with ENDF/B-VII.0 underestimated by 35%. It was concluded that the function can be applied in compact neutron source designs.

Benchmark of neutron production cross sections with Monte Carlo codes

Abstract Aiming to provide critical information in the fields of heavy ion therapy, radiation shielding in space, and facility design for heavy-ion research accelerators, the physics models in three Monte Carlo simulation codes – PHITS, FLUKA, and MCNP6, were systematically benchmarked with comparisons to fifteen sets of experimental data for neutron production cross sections, which include various combinations of 12C, 20Ne, 40Ar, 84Kr and 132Xe projectiles and natLi, natC, natAl, natCu, and natPb target nuclides at incident energies between 135 MeV/nucleon and 600 MeV/nucleon. For neutron energies above 60% of the specific projectile energy per nucleon, the LAQGMS03.03 in MCNP6, the JQMD/JQMD-2.0 in PHITS, and the RQMD-2.4 in FLUKA all show a better agreement with data in heavy-projectile systems than with light-projectile systems, suggesting that the collective properties of projectile nuclei and nucleon interactions in the nucleus should be considered for light projectiles. For intermediate-energy neutrons whose energies are below the 60% projectile energy per nucleon and above 20 MeV, FLUKA is likely to overestimate the secondary neutron production, while MCNP6 tends towards underestimation. PHITS with JQMD shows a mild tendency for underestimation, but the JQMD-2.0 model with a modified physics description for central collisions generally improves the agreement between data and calculations. For low-energy neutrons (below 20 MeV), which are dominated by the evaporation mechanism, PHITS (which uses GEM linked with JQMD and JQMD-2.0) and FLUKA both tend to overestimate the production cross section, whereas MCNP6 tends to underestimate more systems than to overestimate. For total neutron production cross sections, the trends of the benchmark results over the entire energy range are similar to the trends seen in the dominate energy region. Also, the comparison of GEM coupled with either JQMD or JQMD-2.0 in the PHITS code indicates that the model used to describe the first stage of a nucleus-nucleus collision also affects the low-energy neutron production. Thus, in this case, a proper combination of two physics models is desired to reproduce the measured results. In addition, code users should be aware that certain models consistently produce secondary neutrons within a constant fraction of another model in certain energy regions, which might be correlated to different physics treatments in different models.

Neutron Production in Solar Flares by Reactions of Accelerated 3He

Abstract Previously, we showed that 3He is enhanced in the ion population accelerated in large solar flares, with a 3He/4He ratio of &gt;0.1; i.e., several orders of magnitude larger than the accepted coronal value. We also showed that when 3He is enhanced, its nuclear reactions with elements of the solar atmosphere can significantly impact both positron production (and the subsequent positron-annihilation line) and the gamma-ray de-excitation-line spectrum. Both the 2.223 MeV neutron-capture line and escaping neutrons are important additional flare observables. Neutron production from reactions of 3He with heavy elements of the solar atmosphere are not currently included in our neutron-production code, and the reliable and consistent analysis of all available solar-flare data requires that neutron-production calculations include these reactions. We evaluate the neutron-production cross sections for these reactions and include them in the code. We then explore how the neutron observables (the escaping-neutron yield and spectrum and the flux of the neutron-capture line) are affected by 3He reactions. We find that neutron production by accelerated 3He reactions with heavy elements is similar to that by accelerated 4He and so will be significant only for accelerated 3He/4He ratios greater than 1.

Neutron production cross sections for (d,n) reactions at 55 MeV

Neutron production cross sections for (d,n) reactions at 55 MeV