Measurements Of Reaction Cross Sections Research Articles

A Micromegas-based gaseous detector for neutron-induced charged-particle reaction studies in nuclear astrophysics

The quasistellar neutron spectrum produced via 7Li (p, n)7Be reaction at a proton energy of 1.912 MeV has been extensively studied and employed reaction for neutron-induced reaction studies. We are working towards using this reaction at various proton energies from 1.9 MeV to 3.6 MeV to produce a neutron field at a temperature range of ∼ 1.5–3.5 GK to conduct measurements of neutron-induced charge particle reaction cross sections on various unstable nuclei at explosive stellar temperatures. In this paper, we are reporting our design and simulation study with regards to experimental set-up and a gaseous detector with a segmented Micromegas detector for conducting neutron-induced charge particle reactions studies for nuclei of astrophysics importance, for example, 26Al(p, n)26Mg, 26Al(n, α)23Na and 40K(p, n)40Ar, 40K(n, α)37Cl reactions. We plan to perform our experiments with a 10-μA proton beam at the Physikalisch Technische Bundesanstalt facility (PTB, Germany), with a Micromegas-based gaseous detector under construction as discussed in the paper.

Methodology for measuring photonuclear reaction cross sections with an electron accelerator based on Bayesian analysis

Accurate measurements of photonuclear reaction cross sections are crucial for a number of applications, including radiation shielding design, absorbed dose calculations, reactor physics and engineering, nuclear safeguard and inspection, astrophysics, and nuclear medicine. Primarily motivated by the study of the production of selected radionuclides with high-energy photon beams (mainly 225Ac, 47Sc, and 67Cu), we have established a methodology for the measurement of photonuclear reaction cross sections with the microtron accelerator available at the Swiss Federal Institute of Metrology (METAS). The proposed methodology is based on the measurement of the produced activity with a High Purity Germanium (HPGe) spectrometer and on the knowledge of the photon fluence spectrum through Monte Carlo simulations. The data analysis is performed by applying a Bayesian fitting procedure to the experimental data and by assuming a functional trend of the cross section, in our case a Breit-Wigner function. We validated the entire methodology by measuring a well-established photonuclear cross section, namely the 197Au(γ, n)196Au reaction. The results are consistent with those reported in the literature.

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

A Segmented Total Energy Detector (sTED) optimized for (n, [formula omitted]) cross-section measurements at n_TOF EAR2

The neutron time-of-flight facility n_TOF at CERN is a spallation source dedicated to measurements of neutron-induced reaction cross-sections of interest in nuclear technologies, astrophysics, and other applications. Since 2014, Experimental ARea 2 (EAR2) is operational and delivers a neutron fluence of ∼4⋅107 neutrons per nominal proton pulse, which is ∼50 times higher than the one of Experimental ARea 1 (EAR1) of ∼8⋅105 neutrons per pulse. The high neutron flux at EAR2 results in high counting rates in the detectors that challenged the previously existing capture detection systems. For this reason, a Segmented Total Energy Detector (sTED) has been developed to overcome the limitations in the detector’s response, by reducing the active volume per module and by using a photo-multiplier (PMT) optimized for high counting rates. This paper presents the main characteristics of the sTED, including energy and time resolution, response to γ-rays, and provides as well details of the use of the Pulse Height Weighting Technique (PHWT) with this detector. The sTED has been validated to perform neutron-capture cross-section measurements in EAR2 in the neutron energy range from thermal up to at least 400 keV. The detector has already been successfully used in several measurements at n_TOF EAR2.

Spectral analysis techniques in measuring neutron-induced gamma production cross-section

In neutron reaction cross-section measurements, the prompt gamma ray method is a method of obtaining cross-section data by measuring the characteristic gamma rays emitted by a nuclear reaction, thereby avoiding the interference generated by competing reaction channels. However, the prompt gamma ray method is an on-line experiment with abundant background sources, high background counts of the obtained experimental spectra, and numerous interferences such as weak peaks, overlapping peaks, Compton scattering peaks, and neutron effect peaks of Ge in HPGe, which cause the difficulty in analysing the on-line experimental spectra and the high uncertainty in the results. In this work, we study and summarise the spectrum analysis techniques of the prompt gamma ray method that can be used for measuring the neutron cross-section, and comprehensively consider the physical processes of the formation of different characteristic peaks of the prompt gamma ray method, so as to reduce the uncertainty of calculating the net area of the effect peaks in the process of on-line experimental spectrum processing. The Compton edge, weak peaks, overlapping peaks, and the neutron response peaks of the HPGe detector on-line experiment are discussed and analysed, and the net area of the effect peaks is accurately extracted by combining several reasonable functions to fit the total energy peak, the background, and the interferences. For the net area of weak peaks, this method can reduce the peak area selection caused fluctuation from 30% to less than 1%, and the difference between the fitted value of the net area and the theoretical value is comparable to the statistical uncertainty; for the overlapping peaks’ decomposition, the difference between the results obtained by this method and the theoretical value is significantly lower than 1%. The reliability of the spectral analysis method is simultaneously verified by efficiency curve analysis and goodness-of-fit calculation.

Experimental 7Be production cross section from the [formula omitted] reaction at Ep = 3.5 − 13 MeV

The Li7(p,n)7Be reaction is widely used as neutron source for neutron induced reaction cross section measurements, and for 7Be radioactive source production. There are two prominent structures in the excitation function, a narrow resonance between Ep=2.2−2.3 MeV, and a broad peak, around Ep=5 MeV. There are tension between the experimental data sets both in the position and the width of this latter structure, as well as in the absolute scale of the data. In the present work the Li7(p,n)7Be reaction is investigated using the activation technique, with the aim of providing comprehensive cross section data covering the second structure and connecting prior literature data sets. The irradiations were performed with the Atomki cyclotron accelerator with pairs of thin foil targets, thus with precisely controlled reaction energy in the range of Ep=3.5−13 MeV. After the irradiations the activity of the samples was measured using a high-purity germanium detector. The energy uncertainty of the new data points is much smaller than in any of the previous works, while the cross section uncertainty is comparable with the most precise literature data. A consistent data set was obtained connecting the most recent and most precise literature data sets. With the new data the absolute magnitude of the Li7(p,n)7Be reaction cross section is constrained and became more precise.

Study of proton capture on carbon-13 isotope at LUNA

13C(p,γ)14N is a key reaction in different stellar environments for which both accurate and precise measurements of its cross section are required to constraint stellar models. This is currently ongoing at the Laboratory for Underground Nuclear Astrophysics where in addition to the low-background environment, the use of different detection systems (HPGe and BGO detectors) and analysis techniques (Peak Shape Analysis and Sum Peak Method) allowed to perform reaction cross section measurements at the lowest energy ever. Both the setup employed in the measurements and the analysis performed are presented in this paper.

Prospect for measurements of (γ, n) reaction cross-sections of p-nuclei at ELI-NP

The gamma beam system under construction at the ELI-NP facility in Romania is projected to give the nuclear physics community access to an experimental system providing a high-intensity, narrow bandwidth photon beam at variable energy. With high-efficiency detector systems in place, the experimental programme will have a strong potential for in-depth studies of rare stable isotopes originating from the astrophysical p-process. In particular, the neutron detection systems are already implemented through a dedicated 3He long neutron counter array, called ELIGANT-TN, that is completed and in use. In this mini-review, we will give a summary of the current status of existing (γ, n) cross-section data, as well as the methods to obtain them, and highlight the future potential to expand and improve such data using the ELI-NP instrumentation and beam-lines.

Measurement of the [formula omitted] and [formula omitted] reaction cross-sections and isomeric ratios induced by the 14.8 MeV neutrons

The precise measurement of the (n, 2n) reaction cross-sections of xenon isotopes is of great significance for the diagnosis of the Inertial Confinement Fusion fuel area density ρR. The preparation of xenon samples and how they can be efficiently adsorbed to obtain an optimal reaction cross section are extremely difficult in existing experiments. This work aims to use the 93Nb(n,2n)92mNb reaction cross section as the standard to calculate the cross-sections and isomeric ratio for 134Xe(n,2n)133m,gXe and 136Xe(n,2n)135m,gXe reactions. This work also aims to explore the feasibility of adsorbent selection, the method of adsorption sample and the feasibility of the method used in the laboratory. In this paper, the Geant4 program was used to simulate and calculate the adsorption factors of activated carbon and polymer for standard 152Eu multi-line sources, so as to determine the most suitable adsorption material. Next, the GammaVision analysis software was used to observe whether the characteristic γ-rays released by other isotope reaction products of xenon in the sample and packaging material had an effect on the characteristic γ-rays of the target product. Then, the basic principle of activation method and the relative measurement principle are used to calculate the cross-sections and isomeric ratio for 134Xe(n,2n)133Xe and 136Xe(n,2n)135Xe reactions. Finally, the experimental results are compared and analyzed with the existing data in EXFOR database to verify whether the experimental method is correct.

Measurement of alpha-induced reaction cross-sections for [formula omitted]Zn with detailed covariance analysis

The production cross-section of 68Ge, 69Ge, 65Zn and 67Ga radioisotopes from alpha-induced nuclear reaction with natZn have been measured using the stacked foil activation technique followed by the off-line γ-ray spectroscopy in the incident alpha energy range 14-37 MeV. The obtained nuclear reaction cross-sections are compared with previous experimental data available in the EXFOR data library, evaluated nuclear data from TENDL-2019 and theoretical results, calculated using TALYS nuclear reaction code. We have also performed the detailed uncertainty analysis for these nuclear reactions and their respective correlation metrics are presented. Since α-induced reactions are important in nuclear medicine and developing the nuclear reaction codes so needful corrections related to the coincidence summing factor and the geometric factor have been considered during the data analysis in the present study.

Measurement of the (n, 2n) reaction cross-sections of iodine and cesium induced by D-T neutrons with covariance analysis* *Supported by the Key Laboratory of Nuclear Data Foundation (JCKY2022201C151), and the National Natural Science Foundation of China (11975113).

The cross-sections of the 127I (n, 2n) 126I and 133Cs (n, 2n) 132Cs reactions at neutron energies of 13.83 ± 0.05, 14.33 ± 0.10, and 14.79 ± 0.10 MeV were measured relative to the 93Nb (n, 2n) 92mNb reaction using the activation technique in combination with off-line γ-ray spectrometry. A neutron beam was generated from the T (d, n) 4He reaction using the K-400 neutron generator at the China Academy of Engineering Physics. Considering the correlations between different attributes, detailed uncertainty propagation was performed using covariance analysis, and the cross-sections were reported with their uncertainties and correlation matrix. The uncertainty of the measurement cross-sections ranged from 4.84 to 5.90%, which is lower than previous experimental data. Furthermore, the theoretical excitation functions of the 127I (n, 2n) 126I and 133Cs (n, 2n) 132Cs reactions were calculated using the TALYS-1.95 and EMPIRE-3.2.3 codes. Then, the experimentally determined cross-sections were analyzed by comparing them with literature data available in the EXFOR database and evaluated nuclear data in the ENDF/B-VIII.0, JEFF-3.3, JENDL-5, BROND-3.1, CENDL-3.2, and TENDL-2021 databases. Compared with the values previously reported in the 13.8-14.8 MeV energy region, the precision of the results obtained in this study was greatly improved. The current experimental results with thorough uncertainties and covariance information are critical for verifying the reliability of the theoretical model and improving the quality of the nuclear database.

Recoil Proton Telescopes and Parallel Plate Avalanche Counters for the 235U(n,f) cross section measurement relative to H(n,n)H between 10 and 450 MeV neutron energy

With the aim of measuring the 235U(n,f) cross section at the n_TOF facility at CERN over a wide neutron energy range, a detection system consisting of two fission detectors and three detectors for neutron flux determination was realized. The neutron flux detectors are Recoil Proton Telescopes (RPTs), based on scintillators and solid state detectors, conceived to detect recoil protons from the neutron-proton elastic scattering reaction. This system, along with a fission chamber and an array of parallel plate avalanche counters for fission event detection, was installed for the measurement at the n_TOF facility in 2018, at CERN.An overview of the performances of two RPTs — especially developed for this measurement — and of theparallel plate avalanche counters are described in this article. In particular, the characterizationin terms of detection efficiency by Monte Carlo simulations and response to neutron beam, the studyof the background, dead time correction and characterization of the samples, are reported. Theresults of the present investigation show that the performances of these detectors are suitable foraccurate measurements of fission reaction cross sections in the range from 10 to 450 MeV.

The light charged particle detector array at the CSNS Back-n white neutron source

The Back-n white neutron source at the China Spallation Neutron Source (CSNS) provides neutrons in the continuous energy region from 0.5 eV to 200 MeV. A spectrometer named Light charged Particle Detector Array (LPDA) is designed for the study of (n, lcp) reactions at Back-n. The main detector of the LPDA spectrometer, a 16-unit ΔE-ΔE-E telescope array, is composed of two arrays of 8-unit ΔE-ΔE-E telescope. Each telescope unit consists of a Low-Pressure Multi-Wire Proportional Chamber (LPMWPC), a Si-PIN detector, and a CsI(Tl) scintillator detector. In 2021, a neutron-proton (n-p) scattering reaction cross-section measurement experiment was accomplished as the first experiment of the telescope array. Protons can be clearly identified in the ΔE-E spectrum (LPMWPC + Si-PIN) and the ΔE-E spectrum (Si-PIN + CsI(Tl)). Cross sections of the n-p scattering reaction in the neutron energy range of several MeV are extracted. The ΔE-E method also provides new measurement opportunities for many-body neutron induced light charged-particle emission reactions.

Research on the application of pulse shape discrimination method in (n, lcp) reaction cross-section measurements

The China Spallation Neutron Source Back-n white neutron source supplies neutrons with a wide energy range for nuclear data measurements and nuclear techniques. In cross-section measurements of neutron induced light charged-particle emission (n, lcp) reactions at Back-n, the identification of charged particles are usually achieved with the ΔE-E method or a two-dimensional spectrum of the signal amplitude of the particles deposited in the detector and the corresponding neutron energies derived from the time of flight, called amplitude-En method. Nevertheless, a deficiency still exists in the measurement range and the identification performance with these methods. The pulse shape discrimination (PSD) method with a silicon detector is supposed to be a supplement to the amplitude-En and ΔE-E methods. With silicon detectors, experiments have been performed to compare the performance of the amplitude-En and the PSD methods. The PSD method shows a good performance in identifying light charged particles in the MeV neutron energy region. Alphas and tritons emitted from 6Li(n, t) reaction can be identified with the low energy threshold around 2.5 MeV. This provides an effective method for the cross-section measurement of (n, lcp) reactions at Back-n.

Deuteron and α-particle-induced nuclear reactions on 45Sc: activation cross section measurement and thick target yield evaluation

Systematic measurements of nuclear reaction cross sections were done in the low energy range for the two reactions 45Sc(d,p)46Sc and 45Sc(α,n)48V. Thin foils of high-purity (99.95%) natural Sc targets (100% 45Sc), purchased from Good-Fellow, were irradiated with 10 and 20 MeV incident deuteron and α-particle energies, respectively, at beam current of 100 nA using MGC-20 cyclotron. For precise measurements, high-purity Ti and Cu foils were used for monitoring the actual deuteron and α-particle beam intensities, respectively. The conventional stacked-foil technique was applied for measurement and calculation of the cross section values using a high-resolution γ-ray spectrometer for measuring the radioactivity. Nuclear model code EMPIRE-3.2 was used for calculation of the investigated excitation functions. The obtained results were compared with the experimental values and TENDEL-2021 data which are based on TALYS-1.96 code calculations. The integrated yields for the two reactions, based on the proposed average excitation functions, were estimated.

Indirect measurements of neutron-induced reaction cross sections at storage rings

Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars. However, their measurement is very difficult due to the radioactivity of the targets involved. We propose to circumvent this problem by using for the first time the surrogate reaction method in inverse kinematics at heavy-ion storage rings. In this contribution, we describe the developments we have done to perform surrogate-reaction studies at the storage rings of GSI/FAIR. In particular, we present the first results of the proof of principle experiment, which we conducted recently at the Experimental Storage Ring (ESR).

MiniBELEN: A modular neutron counter for (𝜶, 𝒏) reactions

miniBELEN is a modular and transportable neutron moderated counter with a nearly flat neutron detection efficiency up to 10 MeV. Modularity implies that the moderator can be reassembled in different ways in order to obtain different types of response. The detector has been developed in the context of the Measurement of Alpha Neutron Yields (MANY) collaboration, which is a scientific effort aiming to carry out measurements of (𝛼, 𝑛) production yields, reaction cross-sections and neutron energy spectra. In this work we present and discuss several configurations of the miniBELEN detector. The experimental validation of the efficiency calculations using 252Cf sources and the measurement of the 27Al(𝛼, 𝑛) 30P reaction is also presented.

A segmented total energy detector (sTED) for (n, γ) cross section measurements at n_TOF EAR2

The neutron time-of-flight facility n_TOF is characterised by its high instantaneous neutron intensity, high-resolution and broad neutron energy spectra, specially conceived for neutron-induced reaction cross section measurements. Two Time-Of-Flight (TOF) experimental areas are available at the facility: experimental area 1 (EAR1), located at the end of the 185 m horizontal flight path from the spallation target, and experimental area 2 (EAR2), placed at 20 m from the target in the vertical direction. The neutron fluence in EAR2 is ˜ 300 times more intense than in EAR1 in the relevant time-of-flight window. EAR2 was designed to carry out challenging cross-section measurements with low mass samples (approximately 1 mg), reactions with small cross-sections or/and highly radioactive samples. The high instantaneous fluence of EAR2 results in high counting rates that challenge the existing capture systems. Therefore, the sTED detector has been designed to mitigate these effects. In 2021, a dedicated campaign was done validating the performance of the detector up to at least 300 keV neutron energy. After this campaign, the detector has been used to perform various capture cross section measurements at n_TOF EAR2.

Measurement of excitation functions for nat Cu(α, x) reactions with detailed covariance analysis

The excitation functions of 66Ga, 67Ga, 65Zn and 64Cu radioisotopes produced via alpha-induced reaction on nat Cu were measured using a stacked foil activation method. The gamma-ray activity produced by the above mentioned radionuclides was measured using the HPGe detector. The covariance analysis was performed to quantify the measured cross-section uncertainties as well as the correlation between different alpha energy cross-sections. A covariance matrix and cross-sections for the nat Cu(α, x)66Ga, nat Cu(α, x)67Ga, nat Cu(α, x)65Zn and nat Cu(α, x)64Cu nuclear reactions in the projectile energy range of 15–37 MeV are reported in the present work. The measured reaction cross-sections are compared with the existing experimental data and theoretically simulated results from the TALYS code.

First near-threshold measurements of the C13(α,n1)O16 reaction for low-background-environment characterization

The modeling of background sources in large volume detection systems requires accurate nuclear cross sections for a variety of reactions. Among the most important are $(\ensuremath{\alpha},n)$ on light nuclei, where $\ensuremath{\alpha}$ particles, up to $\ensuremath{\approx}9$ MeV, are produced from the decay of actinides present in trace amounts in detection and structural material. In order to model the neutron energy spectra and production of other secondary particles, the partial cross sections are needed. Yet very little experimental data exists for these partial cross sections because past measurements, hampered by the experimental challenges of neutron detection, have focused mostly on total reaction cross section measurements. Here the partial cross section of the $^{13}\mathrm{C}(\ensuremath{\alpha},{n}_{1})^{16}\mathrm{O}$ reaction is reported for the first time. The measurements were made near the reaction threshold using a high energy resolution helium spectrometer. The measurements show a rapidly increasing cross section, which quickly becomes a significant fraction of the total reaction cross section. Measurements are compared with previous theory estimates and differences of more than an order of magnitude are found. A comparison is made with new total cross section measurements and the current level of consistency is demonstrated.