High Precision Cross Sections Research Articles

Characterization of the FOOT neutron detectors for nuclear fragmentation measurements at the n_TOF facility

FOOT (FragmentatiOn Of Target) is an applied nuclear physics experiment with the aim of performing high precision cross section measurements for fragmentation reactions of interest in hadrontherapy and radiation protection in space. The physics program of the experiment foresees a set of measurements with light ion beams, such as C and O, in the energy range of 100–800 MeV/u interacting with tissue-like and shielding material targets. The setup was initially conceived for the detection of charged fragments and, in 2021, the Collaboration started the study of possible solutions for neutron detection. Two detection systems have been proposed: one based on BC-501A liquid scintillators with neutron/γ discrimination capabilities and a system based on BGO crystals operated in phoswich mode. In 2022, a dedicated data acquisition campaign was carried out at the n_TOF facility at CERN to evaluate the capabilities of the two systems. First, the neutron/γ discrimination efficiency of the BC-501A system was studied using radioactive sources. Then, the two systems were placed in the n_TOF experimental area to study their neutron detection efficiency under a well characterized neutron beam. In this work, the first preliminary results concerning the characterization of the two possible neutron detectors of FOOT are presented.

Generating multi-group cross-sections using continuous-energy Monte Carlo method for fast reactor analysis

The deterministic two-step method, comprising multigroup cross-section generation and core calculation, is widely applied in fast reactor design and analysis. Monte Carlo (MC) methods with continuous energy and fine geometry provide high-precision cross-sections essential for advanced fast reactor neutronics analysis. This paper presents an analysis of integrating MC-generated homogenized cross-sections with various core solvers, demonstrating their effectiveness and potential improvements in fast reactor simulations. For diffusion core calculations, the superhomogénéisation (SPH) technique reduces control rod worth overestimation from 13.5% to 0.35% in the MET-1000 benchmark, improving power distribution predictions. In transport core calculations, the flux-moment homogenization technique (MHT) addresses reactivity overestimation by incorporating cross-section anisotropy, reducing error by 698 pcm. For Method of Characteristics (MOC) core calculations, transport-corrected multigroup cross-sections yield high precision in pin-by-pin power distribution for a 100 MWe lead-based fast reactor benchmark. While MC methods require significant computational resources, such as 62 CPU-hours for the MET-1000 core and 85.5 CPU-hours for the 100 MWe lead-based fast reactor core, they offer flexibility in geometry modeling. This work highlights MC multigroup cross-section generation methods applicable to diffusion, MOC, and transport core calculations for fast reactor analysis, suggesting further exploration into their performance in various reactor parameters and computational efficiency.

Constrained model assumptions using recent data of α-particle reactions on 144Sm

Analysis of the latest high–precision cross sections of (α,γ) and (α,n) reactions on 144Sm below the Coulomb barrier is carried out using a consistent parameter set of the statistical model. This prevents the need to use empirical rescaling factors of either γ or neutron widths. Particular attention is paid to uncertainties of the calculated cross sections which are related to the accuracy of the primary data that were used to set up the consistent input parameters. The calculated cross sections are found in good agreement with the new experimental data for the 144Sm(α,n)147Gd reaction; however, the same is not true for the excitation function of 144Sm(α,γ)148Gd which decreases faster at incident energies below ∼12 MeV. An increase of the α-particle direct collective inelastic scattering at lower energies is found responsible for this decrease of the (α,γ) reaction cross sections. The consequent lower nuclear effects may correspond to the Coulomb excitation effect assumed, although in a different manner, within the so-called “α-potential mystery” for the same optical–potential account of α-particle absorption and emission as well.

Monitored neutrino beams and the next generation of high precision cross section experiments

The main source of systematic uncertainty on neutrino cross section measurements at the GeV scale originates from the poor knowledge of the initial flux. The reduction of this uncertainty to 1% can be achieved through the monitoring of charged leptons produced in association with neutrinos. The goal of the ENUBET ERC project is to prove the feasibility of such a monitored neutrino beam. In this contribution, the final results of the ERC project, together with the complete assessment of the feasibility of its concept, are presented. An overview of the detector technology for a next generation of high precision neutrino-nucleus cross section measurements, to be performed with the ENUBET neutrino beam, is also given.

High-precision cross sections measurement of (n,2n) reactions on 124Xe and 78Kr isotopes in the 14 MeV region

The cross sections of 124Xe(n,2n)123Xe and 78Kr(n,2n)77Kr reactions were measured at 7 neutron energies between 13 MeV and 15 MeV. A self-designed improved organic-glass gas target was introduced to reduce both the effect of γ-ray absorbing and the uncertainty of nucleus quantification. The monoenergetic neutrons were generated via the 3H(d,n)4He reaction with a solid T-Ti target, and reactions 93Nb(n,2n)92mNb were adopted as neutron flux monitors. The cross sections obtained in this work achieve the least uncertainty compared with the literatures, which are beneficial in providing better experimental constraints for the excitation curves prediction, thus improving the quality of the corresponding database. Meanwhile, these two data sets could also be used as a nuclear physics based diagnostic tool for studying properties of the deuterium-tritium plasma created in inertial confinement fusion reactions.

Cutting of optical fibers using a Bessel profile femtosecond laser

A high-quality cutting surface is one of the necessary conditions for the realization of labs on fibers, which is a prerequisite for optical fiber welding, coupling, and integration. This study investigates a method for obtaining high-precision cross-sections of a variety of fibers using a femtosecond laser. The laser beam was shaped from a Gaussian profile to a Bessel profile, and an optimized position of the focal beam was selected for fiber cutting. Micromachining parameters analysis and corresponding cutting cross-section characterizations are demonstrated, providing a reference for cutting optical fibers of different structures with a femtosecond laser.

Charge identification of nuclear fragments with the FOOT Time-Of-Flight system

FOOT (FragmentatiOn Of Target) is an applied nuclear physics experiment conceived to conduct high-precision cross section measurements of nuclear fragmentation processes relevant for particle therapy and radiation protection in space. These measurements are important to estimate the physical and biological effects of nuclear fragments, which are produced when energetic particle beams penetrate human tissue.A component of the FOOT experiment is the ΔE-TOF system. It is designed to measure energy loss and time-of-flight of nuclear fragments produced in particle collisions in thin targets in order to extract their charge and velocity. The ΔE-TOF system is composed of a start counter, providing the start time for the time-of-flight, and a 40 × 40 cm2 wall of thin plastic scintillator bars, providing the arrival time and energy loss of the fragments passing through the detector. Particle charge discrimination can be achieved by correlating the energy loss in the scintillator bars with the measured time-of-flight.Recently, we have built a full-size ΔE-TOF detector. In this work, we describe the energy and time-of-flight calibration procedure and assess the performance of this system. We use data acquired during beam tests at CNAO with proton and 12C beams and at GSI with 16O beams in the energy range relevant for particle therapy, i.e., from 60 to 400 MeV/u. For heavy fragments (C and O), we obtain energy and time resolutions ranging from 4.0 to 5.2% and from 54 to 76 ps, respectively. The procedure is also applied to a fragmentation measurement of a 400 MeV/u 16O beam on a 5 mm carbon target, showing that the system is able to discriminate the charges of impinging fragments.

Cross section measurement of neutron capture reaction based on back-streaming white neutron source at China spallation neutron source

The data of neutron capture cross section are very important for the research of nuclear astrophysics, advanced nuclear energy development. Owing to the limitation of neutron source and detector, the experimental data of neutron capture cross section in an energy range of 1 eV–10 keV were almost blank in China. The first Chinese gamma-ray total absorption facility has been constructed in the key laboratory of nuclear data at China institute of atomic energy, which consists of 40 BaF<sub>2</sub> detector units. The BaF<sub>2</sub> crystal shell with a thickness of 15 cm and an inner radius of 10 cm covers 95.2% of the solid angle. On-line measurement method of neutron capture reaction cross section is established on the back-streaming white neutron source of China spallation neutron source by using the upgraded facility. The cross section of <sup>197</sup>Au neutron capture reaction is measured for the first time under the experimental condition of irregular 30 mm neutron beam spot. The measured position of resonance peak is well consistent with the relevant data of ENDF evaluation database, which verifies the reliability of the measurement device and measurement technology, and thus laying the foundation for the acquisition of high precision cross section in future.

Neutron cross section measurements at the n_TOF facility (CERN)

The design of innovative Accelerator Driven Systems (ADS) for incineration of nuclear waste and energy generation requires the complete knowledge of basic cross sections for neutron induced processes. The main goal of the project is to produce, evaluate and disseminate high precision cross sections for the majority of the isotopes relevant to the waste incineration and the ADS design i.e. capture and fission cross sections for the minor actinides, capture cross sections for the main fission products and (η,χη) reactions for structural and coolant materials. The most recent work, (2003-2004 campaign) took place at CERN, using a Total Absorption Calorimeter (TAC) in neutron capture measurements. The TAC was build at n_TOF facility and consists of 40 BaF2 crystals, covering an almost 4π geometry. Several targets of special interest have been measured, such as 233>234U, 241Am, 237Np, 2 4 0Pu and samples for reference and background determination as well (197Au, 2 0 8Pb, natC). Preliminary results of 2 3 7Np and 2 4 0Pu and 2 3 4U will be presented, indicating the good performance of the n_TOF facility, DAQ (Data Acquisition system) and TAC, allowing even more ambitious experiments in the future.

High-Precision Section Control Technology for High-Strength Yoke Steel Strip

The hot-rolled yoke steel plate is used in the manufacture of motor rotors for core components of large generators, which is required to ensure high strength and high-precision plate profile, especially the control of the thickness difference. High-precision cross-section control technology from rough rolling to finishing rolling for high-strength yoke steel is designed. First, through the varying contact backup roll technology and optimization of load distribution in the roughing stand, the profile of transfer bar is improved, which provides the basis for the strip shape control in the finishing mills. Secondly, the approximate rectangular section of a hot strip is obtained by high-precision shape setting and control model for finishing rolling, symmetrical variable taper work roll technology and smart shifting technology in the downstream stands. These methods solve the problem that the shape of the high-strength strip is difficult to control, and significantly enhance the shape regulation ability and control accuracy of the hot-rolled yoke. In addition, this technology has been applied to hot rolling mills with remarkable results and economic benefits.

Nucleon Resonances in $$\varvec{\gamma p \rightarrow K^{*+} \Lambda }$$

We use an effective Lagrangian approach in the tree-level approximation to analyze the high-precision cross-section data for $$\gamma p \rightarrow K^{*+}\Lambda $$ reported by the CLAS Collaboration. Apart from the t-channel K, $$\kappa $$ , $$K^*$$ exchanges, the s-channel nucleon (N) exchange, the u-channel $$\Lambda $$ , $$\Sigma $$ , $$\Sigma ^*(1385)$$ exchanges, and the generalized contact current, we found that at least two nucleon resonances ( $$N^*$$ ’s) should be considered to well describe the high-precision cross-section data. One is the $$N(2060){5/2}^-$$ that is responsible for the shape of the angular distribution near the $$K^*\Lambda $$ threshold via its interference with the t-channel K exchange, and the other could be one of the $$N(2000){5/2}^+$$ , $$N(2040){3/2}^+$$ , $$N(2100){1/2}^+$$ , $$N(2120){3/2}^-$$ and $$N(2190){7/2}^-$$ . The results for $$\Sigma $$ , T and P are predicated and it is pointed out that more data on these observables are needed to further pin down the resonance contents and their associated parameters in this reaction.

Nucleon resonances in γp→K*+Λ

The high-precision cross-section data for the reaction $\gamma p \to K^{*+}\Lambda$ reported by the CLAS Collaboration at the Thomas Jefferson National Accelerator Facility have been analyzed based on an effective Lagrangian approach in the tree-level approximation. Apart from the $t$-channel $K$, $\kappa$, $K^*$ exchanges, the $s$-channel nucleon ($N$) exchange, the $u$-channel $\Lambda$, $\Sigma$, $\Sigma^*(1385)$ exchanges, and the generalized contact term, the contributions from the near-threshold nucleon resonances in the $s$-channel are also taken into account in constructing the reaction amplitude. It is found that, to achieve a satisfactory description of the differential cross section data, at least two nucleon resonances should be included. By including the $N(2060){5/2}^-$ resonance, which is responsible for the shape of the angular distribution near the $K^*\Lambda$ threshold, and one of the $N(2000){5/2}^+$, $N(2040){3/2}^+$, $N(2100){1/2}^+$, $N(2120){3/2}^-$ and $N(2190){7/2}^-$ resonances, one can describe the cross-section data quite well, with the fitted resonance masses and widths compatible with those advocated by the Particle Data Group. The resulted predictions of the beam, target, and recoil asymmetries are found to be quite different from various fits, indicating the necessity of the spin observable data for $\gamma p \to K^{*+}\Lambda$ to further pin down the resonance contents and associated parameters in this reaction.

16O(n,α) cross section investigation using LENZ instrument at LANSCE

Importance of studying the 16 O(n, α ) reaction is motivated by multiple nuclear applications. The Los Alamos Neutron Science Center (LANSCE) produces a white neutron spectrum ranging from thermal to several hundreds of MeV energies. We have recently developed the LENZ (Low Energy NZ-neutron induced charged particle detection) capability to measure high-precision (n, α ) cross sections. In order to provide more reliable data, we have enhanced solid angle coverage, and improved signal-to-noise ratios and time-of-flight resolution by implementing digitizer waveform analysis. The LENZ was commissioned by studying the 59 Co(n, α ) reaction with neutron beams in early 2015. For the 16 O(n, α ) reaction, we investigate solid oxygen targets and make a relative measurement to a better known cross section, such as the 6 Li(n, α ) reaction in order to further reduce systematic uncertainty. We will discuss the progress of the 16 O(n, α ) study at LANSCE and the outlook for improving Hauser-Feshbah prediction on (n,p) reaction cross sections.

Silicon detectors for the neutron flux and beam profile measurements of the n_TOF facility at CERN

The demand of new and high precision cross section data for neutron-induced reactions is continuously growing, driven by the requirements from several fields of fundamental physics, as well as from nuclear technology, medicine, etc. Several neutron facilities are operational worldwide, and new ones are being built. In the coming years, neutron beam intensities never reached up to now will be available, thus opening new scientific and technological frontiers. Among existing facilities, n_TOF at CERN provides a high intensity pulsed neutron beam in a wide energy range (thermal to GeV) and with an extremely competitive energy resolution that also allows spectroscopy studies. In order to ensure high quality measurements, the neutron beams must be fully characterized as a function of the neutron energy, in particular by measuring the neutron flux and the beam transverse profile with high accuracy. In 2014 a new experimental area (EAR2), with a much higher neutron flux, has been completed and commissioned at n_TOF. In order to characterize the neutron beam in the newly built experimental area at n_TOF, two suitable diagnostics devices have been built by the INFN-LNS group. Both are based on silicon detectors coupled with 6Li converter foils, in particular Single Pad for the flux measurement and Position Sensitive (strips and others) for the beam profile. The devices have been completely characterized with radioactive sources and with the n_TOF neutron beam, fulfilling all the specifications and hence becoming immediately operational. The performances of these devices and their high versatility, in terms of neutron beam intensity, make them suitable to be used in both n_TOF experimental areas. A description of the devices and the main results obtained so far will be presented.

SU-E-T-492: High Precision Cross Sections and Physics Models for Proton Interactions Below 20 MeV in Geant4

Purpose: Geant4 is a Monte Carlo (MC) toolkit with an increasing use in the field of medical physics. Electromagnetic processes are well validated, but for hadronic interactions of charged particles at energies of the order of a few MeV, particularly for low Z materials, there are no physics models able to reproduce the experimental data. With the default version of Geant4, the cross sections and production of secondary particles for proton-nucleus interactions at an energy below 20 MeV are not satisfactory. In this study, a new physics package to simulate particles below 20 MeV has been added to Geant4. Methods: A new Geant4 package has been developed to simulate proton interactions below 20 MeV using the data on reaction cross sections and production of secondary particles contained in evaluated nuclear databases. The new package has been tested making use of the TENDL-2009 and TENDL-2012 databases to simulate the 18O(p,x) interactions for energies ranging from 4 MeV up to 20 MeV. For this particular reaction, we have also included in the database the accurate data that can be found in the IAEA medical database. Results: The obtained energy spectra of the secondary particles produced by the 18O(p,n) and 18O(p,gamma) reactions were compared with those calculated with the standard Geant4 physics, QGSP_BIC_HP, and also with suitable MCNPX calculations. The neutron and gamma production obtained with the new Geant4 package and TENDL/IAEA-libraries are significant from 4 MeV, while with the standard Geant4 physics there is no production of neutrons for energy below 8 MeV, while above 8 MeV the gamma and neutron production shows a wrong yield. Conclusion: A new high precision physics package with corresponding cross section libraries have been successfully added to the Geant4 MC toolkit for particle energies below 20 MeV, improving the accuracy and production rates of different secondaries.

Quantification of ontogenetic allometry in ammonoids

Ammonoids are well-known objects used for studies on ontogeny and phylogeny, but a quantification of ontogenetic change has not yet been carried out. Their planispirally coiled conchs allow for a study of "longitudinal" ontogenetic data, that is data of ontogenetic trajectories that can be obtained from a single specimen. Therefore, they provide a good model for ontogenetic studies of geometry in other shelled organisms. Using modifications of three cardinal conch dimensions, computer simulations can model artificial conchs. The trajectories of ontogenetic allometry of these simulations can be analyzed in great detail in a theoretical morphospace. A method for the classification of conch ontogeny and quantification of the degree of allometry is proposed. Using high-precision cross-sections, the allometric conch growth of real ammonoids can be documented and compared. The members of the Ammonoidea show a wide variety of allometric growth, ranging from near isometry to monophasic, biphasic, or polyphasic allometry. Selected examples of Palaeozoic and Mesozoic ammonoids are shown with respect to their degree of change during ontogeny of the conch.

1813 浮動拡管プラグ曲げによる異形断面管の変形特性(OS19-1 金属の板材およびパイプ材の材料特性計測および成形解析の高度化,IOS19 金属の板材およびパイプ材の材料特性計測および成形解析の高度化)

Floating-Expanding-Plug-Bending of pipe is characterized by expanding and shifting of floating plug, both of which are helpfully functioning to the bending, reducing working force and realizing severe bending with high-precision cross section profile. By using this method, a circular pipe is deformed to triangle section with triangle-shape plug In order to obtain the basic characteristics of bending to polygonal section pipe, geometric shapes of triangle plug which produce triangle section were investigated. In the experiments, it was realized that the plug should not have sharp edge and circular aspect to form triangle bent pipes. Both bending and expanding completed at the same time on the bending method. In this research, deformation behavior of metal materials in Floating-Expanding-Plug Bending was also analyzed with FEM analysis and experiment.

Comment on “High-Precision Determination of the Electric and Magnetic Form Factors of the Proton”

In a recent Letter, Bernauer, et al. present fits to the proton electromagnetic form factors, GEp(Q^2) and GMp(Q^2), along with extracted proton charge and magnetization radii based on large set of new, high statistical precision (<0.2%) cross section measurements. The Coulomb corrections they apply differ dramatically from more modern and complete calculations, implying significant error in their final results.

THREE-NUCLEON INTERACTION DYNAMICS STUDIED VIA THE DEUTERON-PROTON BREAKUP

Rich sets of high precision cross sections, vector and tensor analyzing powers for the [Formula: see text] breakup reaction were measured at 130 and 100 MeV beam energy with the use of detection systems covering large parts of the phase space. The cross section data allowed to establish evidences for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force in the breakup reaction. Analyzing power data are generally quite well described by theoretical predictions even with pure nucleon-nucleon interactions. However, in some regions discrepancies has been observed for tensor analyzing powers at 130 MeV.

Characterization of an INVS model IV neutron counter for high precision cross-section measurements

Characterization of an INVS model IV neutron counter for high precision cross-section measurements