Measurements Of Reaction Cross Sections Research Articles

Studying multi-nucleon transfer reaction in a recoil mass spectrometer

We present simulation of a recoil mass spectrometer for measurement of multi-nucleon transfer reactions, based on Monte Carlo techniques. Target-like ions are generated event by event and transported to the focal plane of the spectrometer by the method of transfer matrices. Measured focal plane spectra for the elastic and six transfer channels of the reaction $$^{28}$$ Si+ $$^{94}$$ Zr are reproduced at two projectile energies near the Coulomb barrier. Excellent reproduction is achieved even with first-order ion-optical calculations, indicating not so significant role of higher order aberrations in conventional recoil separators with smaller acceptance. This is in striking contrast with the large acceptance magnetic separators used for studying transfer reactions, for which complex trajectory reconstruction algorithms involving higher order aberrations are essential. Transmission efficiency of the spectrometer, calculated by the reported code, is crucial to convert measured transfer probabilities to differential and integral transfer cross sections for each channel. We show effectiveness of the proposed methodology by extracting differential elastic scattering cross sections from measured yields for the reaction $$^{28}$$ Si+ $$^{94}$$ Zr. Besides being useful for other recoil mass spectrometers, our methodology can be employed for measurement of quasi-elastic reaction cross sections in velocity filters and gas-filled separators.

Measurements of total reaction cross sections for 17Ne using a solid hydrogen target

We measured the energy dependence of the total reaction cross sections (σR) for the proton-drip-line nucleus,17Ne, using a solid hydrogen target. We compared the experimental data with theoretical calculations using the Glauber model. We found that the theoretical cross sections overestimate the experimental ones in the low-energy region (∼100A MeV), whereas they significantly underestimate the experimental data in the intermediate-energy region (∼300-500A MeV). These trends are the same as those for σR for carbon-proton collisions, which were measured previously. We discuss several possibilities for resolving this discrepancy. This work demonstrates the necessity of additional careful investigations of the energy dependence of σR for various nuclei on proton targets in order to determine nuclear size properties precisely.

Experimental programme with high-brilliance gamma beams at ELI-NP

The emerging experimental program with brilliant gamma beams at the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) facility is presented with emphasis on the day-one experiments which are under preparation. Experiments at ELI-NP will cover nuclear resonance fluorescence (NRF) measurements, studies of large-amplitude motions in nuclei, photo-fission and photonuclear reactions of astrophysics interest, and measurements of photonuclear reaction cross-sections. The physics cases of the flagship experiments at ELI-NP and the performance of the related instruments, which are under construction for their realization, are discussed.

Charge-changing cross section measurements of atomic nuclei and charge radii

<p indent=0mm>The atomic nucleus is a finite open quantum many-body system that is composed of two basic building blocks, proton and neutron. Like many systems governed by the laws of quantum mechanics, a nucleus is an object full of mysteries. Nuclear properties and structure are much more difficult to characterize than those of macroscopic objects and it is almost impossible to build an exact replica of this Fermi-scale nuclear system. In reality, physicists have developed an approach to reveal nature by collisions of two atomic nuclei, i.e., nuclear reactions, since the very beginning of nuclear physics. One famous example is the Rutherford scattering experiment performed at around 1910, in which the nuclide as a core of atom was discovered. Since the late 1980s, precision measurements of reaction cross section or interaction cross sections played a crucial role in nuclear size determination. This was entwined with the realization of radioactive ion beams (RIB). Such measurements contributed to discovering, for example, the neutron skin and neutron halo, when moving far away from the stability line. The new phenomena and properties found along the experimental advance are meanwhile among the strongest motivations for initiating, constructing, and operating the new generations of nuclear physics facilities worldwide. HIAF, the High-Intensity heavy-ion Accelerator Facility, is now under construction in Huizhou, China. In the last few years, systematic measurements of charge-changing cross sections (CCCS) of exotic nuclei have attracted much attention. It offers a complementary way to study exotic structures that could exist in exotic nuclei. By definition, CCCS refers to the total probability of removing at least one proton from the projectile nuclide. It reflects the geometric overlapping area during the collision. In particular, by combining with the Glauber-type model calculations, precise CCCS data have been used as an effective probe to investigate the proton density distribution of unstable atomic nuclei. This method is suitable for the investigation of exotic nuclei with low production yields, and the measurements accordingly were proposed in almost all the major nuclear physics facilities in the last years. In this paper, we first attempted to give a review on the progress of CCCS worldwide, from the pioneering work of RIB physics in the 1980s to the recent advances towards neutron-rich nuclei. Then we introduced the experimental work performed at the Heavy Ion Research Facility at Lanzhou (HIRFL). So far, CCCSs of more than 30 light nuclei have been determined and most of them are along the β-stability line. Based on the same setup, the Beihang group will focus on the CCCS measurements of sd-shell nuclei, aiming to study the (sub-)shell structure at 14 and 16. After surveying the existing CCCS data worldwide, it is found that there are often large deviations among various measurements in different laboratories even for the simplest reaction system. Precision data are therefore urgently called to clarify the deviations in existing data and to constrain the reaction mechanism on hydrogen targets. From my point of view, simultaneous measurements of both CCCS and reaction cross section in particular on hydrogen targets, the simplest target composed of only protons, are expected to enhance dramatically the journey to reveal the nature of very exotic nuclei. In the last part of this paper, perspectives at the High-energy FRagment Separator (HFRS) at HIAF are discussed. After a careful design of the detector setup and data taking system, it is possible to open a new era of nuclear physics experiments, in which various types of experiments can be carried out simultaneously.

Experimental Measurement Method of Beta Decay Strength of Unstable Nuclei

The β decays of atomic nuclei refer to the transformation that the nuclei emit a β particle or capture an electron. The accurate measurements of the β transition strength functions Sβ(E) are of great significance in exploring the structure of unstable nuclei, revealing the process of stellar nucleosynthesis and also verifying the β decay theories. Experimentally, one way to determine the β transition strength is to directly measure the beta decay product using β-γ coincidence technique and/or total absorption spectroscopy. This method can give the transition information within the Qβ window. Another method to obtain the β decay strength is via the charge exchange reactions performed at the intermediate energy region (100~400 MeV/u), such as (p, n) or (3He, t). This is done by a high-precision measurement of the differential cross section. This method allows to access the transition strength that beyond the Qβ window, however, it is restricted by the beam intensity, and as a consequence hard to perform a systematical study of unstable nucleus with low yields. In view of this, in this paper we proposes a systematic measurement of the total charge exchange reaction cross section of the unstable nuclei. Combined with the well developed nuclear reaction theory, this method may set a constrain to the summed strength of the Gamow-Teller transition of the unstable nuclei within the proton separation threshold. Moreover, we introduce briefly the relevant work that has been carried out and planned.

Measurement of 115In(n,2n)114mIn and 197Au(n,2n)196Au reaction cross sections at the neutron energies of 13.52 and 14.54 MeV with covariance analysis

The 115In(n,2n)114mIn and 197Au(n,2n)196Au reaction cross sections have been measured relative to the 27Al(n,α)24Na monitor reaction at the two different incident neutron energies of 13.520 ± 0.005 MeV and 14.54 ± 0.24 MeV. The neutrons from the D-T fusion reaction at the Purnima neutron generator were used for activation followed by off-line γ-ray spectrometry. The uncertainty propagation and correlation of measured reaction cross sections were estimated using covariance analysis through considering the partial uncertainties in different attributes. The measured reaction cross sections from the present work have been compared with the literature data from EXFOR compilation, ENDF data of various libraries and theoretically calculated values from the TALYS-1.9 code.

Production of quasi-mono-energetic neutron beams for reaction cross-section measurements: A simulation study

The main objective of the present work is to assess the use of theoretical studies in finding the appropriate working conditions for experiments used in the production of neutron beams. A model has been designed and built using MATLAB programming language to perform the calculations required to generate filtered neutron beams in different energy ranges. The selection of the primary and additive materials has been obtained as a function of the material mass-thickness in g/cm2 to emit high intensity and purity for the desired neutron energies.The development of quasi-mono-energetic neutron beams has been conducted at energies of 5.2, 13.3, 47.0, and 73.0 keV. The generated beams have been evaluated and compared to previous findings on the same energies. Results obtained in the present work enhance the use of these filters in cross-section measurements and BNCT owing to the fact that they have high intensity and purity with reasonable resolution value (ΔE). Moreover, high attenuation of both thermal and fast neutrons except the desired energy value has been observed.

Measurement of 14.54 ± 0.24 MeV neutron activation reaction cross sections of 93Nb, natMo with covariance analysis

The 93Nb(n,α)90mY, 93Nb(n,2n)92mNb and 92Mo(n,p)92mNb reaction cross sections have been measured relative to the 197Au(n,2n)196Au monitor reaction at the neutron energy of 14.54 ± 0.24 MeV. The neutrons were generated from the T(d,n)4He reaction using Purnima neutron generator. The experiment was done by using the method of activation in combination with an off-line $$\gamma$$ -ray spectrometry technique. The uncertainties and correlations for the reaction cross sections were estimated with the use of covariance analysis by considering the partial uncertainties in individual attributes. The measured reaction cross sections have been analyzed by comparing with the data available in EXFOR compilation, various files of evaluated data and theoretically calculated values from TALYS-1.9.

High precision half-life measurement of ^{95}hbox {Ru}, ^{95}hbox {Tc} and ^{95m}hbox {Tc} with gamma -spectroscopy

The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the ^{92}hbox {Mo}(alpha ,n)^{95}hbox {Ru} reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of ^{95}hbox {Ru}, derived about half a century ago, is overestimated. Therefore, the half-lives of ^{95}hbox {Ru} and its daughter isotope ^{95}hbox {Tc} and ^{95m}hbox {Tc} have been measured with high precision using gamma -spectroscopy. The results are hbox {t}_{1/2} =1.6033 pm 0.0044 h for ^{95}hbox {Ru}, hbox {t}_{1/2} =19.258 pm 0.026 h for ^{95}hbox {Tc} and hbox {t}_{1/2} =61.96 pm 0.24 d for ^{95m}hbox {Tc}. The precision of the half-life values has been increased, consequently the recently measured ^{92}hbox {Mo}(alpha ,n)^{95}hbox {Ru} activation cross section will become more precise.

MULTI-2, a 4[formula omitted] spectrometer for total reaction cross section measurements

A detection setup for the direct measurement of the total reaction cross section with exotic nuclei is presented. The setup consists of a multi-detector telescope for beam-particle identification and a 4π gamma-ray spectrometer for the detection of prompt photons and neutrons accompanying the nuclear reactions. Measurements are based on the modified transmission method and gamma-ray tagging of nuclear reaction events. Registration efficiency and response characteristics of the gamma-ray spectrometer are investigated by Monte Carlo simulations and measurement with 60Co spectroscopic source. Results show strong a dependence of the registration efficiency on gamma-ray multiplicity, with minimum registration efficiency value of 70%. Evaluation of the registration efficiency for data measured in the total reaction cross section experiments is discussed.

Two-Neutron Halo is Unveiled in ^{29}F.

We report the measurement of reaction cross sections (σ_{R}^{ex}) of ^{27,29}F with a carbon target at RIKEN. The unexpectedly large σ_{R}^{ex} and derived matter radius identify ^{29}F as the heaviest two-neutron Borromean halo to date. The halo is attributed to neutrons occupying the 2p_{3/2} orbital, thereby vanishing the shell closure associated with the neutron number N=20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of ^{27}F but are challenged for ^{29}F.

Application of a silicon detector array in [formula omitted] reaction cross-section measurements at the CSNS Back-n white neutron source

The Back-n white neutron source at the China Spallation Neutron Source (CSNS) was put into operation in 2018, providing a good platform for the cross-section measurement of neutron induced light charged particle (lcp) emission (n,lcp) reactions. Currently, in order to detect and identify light charged particles produced in (n,lcp) reactions at Back-n, a silicon detector array has been developed as a part of Light-charged Particle Detector Array. Composed of 15 silicon detectors, the array can detect the emitted particles ranging from 19.2°to 160.8°. The energy resolution of each silicon detector unit is better than 1% for 5.499 MeV α particles. Adopting this silicon detector array, several experimental measurements have been completed. Differential cross sections and angle-integrated cross sections in the neutron energy region ranging from the eV to the MeV range are extracted. Compared with previous measurements and evaluations, new results are obtained in the present measurements. These experiments indicate the feasibility of the silicon detector array in (n,lcp) reaction cross-section measurements.

Measurement of (n, xn) reaction cross sections on $$^{113,115}$$In isotopes using quasi-monoenergetic neutrons within 10–20 MeV

Cross section of the $$^{113}$$In$$(n, n')$$$$^{113m}$$In, $$^{115}$$In$$(n, 2n)$$$$^{114m}$$In and $$^{115}$$In($$n, n'$$)$$^{115m}$$In reactions has been measured at average neutron energies of 10.95 ± 0.67, 13.97 ± 0.97, 16.99 ± 0.88 and 20.00 ± 0.94 MeV, using neutron activation analysis followed by the offline $$\gamma $$-ray spectrometric technique. Quasi-monoenergetic neutrons were produced by bombarding natural lithium with proton beam of appropriate energies at the 14UD BARC-TIFR Pelletron facility, Mumbai, India. The present experimental results have been compared with available experimental reaction data in EXFOR, theoretical results of nuclear reaction model code TALYS-1.9 and evaluated data library JENDL/AD. The uncertainty and correlation between the present experimental data have been determined using the ratio technique of covariance analysis. This technique considers the collective error from all the attributes in the measurement. The experimental results discussed in this paper have significant importance in the advancement of reactor technology.

A new approach to monitor $$^{13}\hbox {C}$$-targets degradation in situ for $$^{13}\hbox {C}(\alpha ,\hbox {n})^{16}\hbox {O}$$ cross-section measurements at LUNA

Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section results. A common technique used for these purposes is the Nuclear Resonant Reaction Analysis (NRRA), which however requires that a narrow resonance be available inside the dynamic range of the accelerator used. In cases when this is not possible, as for example the 13C(alpha,n)16O reaction recently studied at low energies at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy, alternative approaches must be found. Here, we present a new application of the shape analysis of primary gamma rays emitted by the 13C(p,g)14N radiative capture reaction. This approach was used to monitor 13C target degradation {\em in situ} during the 13C(alpha,n)16O data taking campaign. The results obtained are in agreement with evaluations subsequently performed at Atomki (Hungary) using the NRRA method. A preliminary application for the extraction of the 13C(alpha,n)16O reaction cross-section at one beam energy is also reported.

Few-body reactions investigated with the Trojan Horse Method

The Trojan Horse Method is an indirect method to measure reaction cross sections at energies of interest for nuclear astrophysics, exploiting the nuclei clustering properties. Here it is presented with its general features and detailed for the case of the ^22H(d,p)^33H and ^22H(d,n)^33He measurements, where interesting results for astrophysics and energy fusion power plants have been obtained.

Global predictions for astrophysics applications

Nuclear reaction rates play a crucial role in nuclear astrophysics. In the last decades there has been an enormous effort to measure reaction cross sections and extensive experimental databases have been compiled as a result. In spite of these efforts, most nuclear reaction network calculations still have to rely on theoretical predic- tions of experimentally unknown rates. In particular, in astrophysics applications such as the s-, r- and p-process nucleosynthesis involving a large number of nuclei and nuclear reactions (thousands). Moreover, most of the ingredients of the cal- culations of reaction rates have to be extrapolated to energy and/or mass regions that cannot be explored experimentally. For this reason it is important to develop global microscopic or semi-microscopic models of nuclear properties that give an accurate description of existing data and are reliable for predictions far away from the stability line. The need for more microscopic input parameters has led to new devel- opments within the Hartree-Fock-Bogoliubov method, some of which are presented in this paper.

Deuteron-induced reactions on manganese at low energies

The scarce data systematics and complexity of deuteron interactions demand the update of both the experimental database and theoretical frame of deuteron activation cross sections. Various reactions induced by neutrons and protons following the deuteron breakup (BU) should be also taken into account. On the other hand, deuteron reaction cross sections recommended recently for high-priority elements are still based on data fit without predictive power. Purpose: Accurate new measurements of low-energy deuteron-induced reaction cross sections for monoisotopic (55Mn) natural manganese target enhance the related database as well as the opportunity of an unitary and consistent account of the related reaction mechanisms. Method: Activation cross sections of 54,56Mn, and 51Cr nuclei by deuterons on $^{55}$Mn were measured at energies <20 MeV by the stacked-foil technique and high resolution gamma spectrometry at the U-120M cyclotron of CANAM, NPI CAS. Then all available data for deuterons on 55Mn up to 50 MeV are analyzed paying particular attention to BU and direct reaction (DR) mechanisms. Results: Newly measured activation cross sections strengthen the deuteron database at low energies, at once with a consistent account for the first time of all available data. Conclusions: Due account of deuteron-induced reactions on 55Mn, including particularly the new experimental data at low energies, is provided by a suitable BU and DR assessment.

MicroMegas-based detectors for time-of-flight measurements of neutron-induced reactions

MicroMegas detectors are versatile gaseous detectors which are used for ionizing particle detection. A MicroMegas detector consists of two adjacent gas-filled volumes. One volume acts as a drift region with an electric field operating in the ionization chamber regime, the second volume is the amplification region acting as a parallel-plate avalanche counter. The use of the microbulk technique allows the production of thin, radiation resistant, and low-mass detector with a highly variable gain. Such MicroMegas detectors have been developed and used in combination with neutron time-of-flight measurements for in-beam neutron-flux monitoring, fission and light-charged particle reaction cross section measurements, and for neutron-beam imaging. An overview of MicroMegas detectors for neutron detection and neutron reaction cross section measurements and related results and developments will be presented.

Study of Astrophysical s-Process Neutron Capture Reactions at the High-Intensity SARAF-LiLiT Neutron Source

We report on recent experiments at the Soreq Applied Research Accelerator Facility Liquid-Lithium Target (SARAF-LiLiT) laboratory dedicated to the study of s-process neutron capture reactions. The kW-power proton beam at 1.92 MeV (1-2 mA) from SARAF Phase I yields high-intensity 30 keV quasi-Maxwellian neutrons (3-5×1010 n/s). The high neutron intensity enables Maxwellian averaged cross sections (MACS) measurements of low-abundance or radioactive targets. Neutron capture reactions on the important s-process branching points 147Pm and 171Tm were investigated by activation in the LiLiT neutron beam and γ-measurements of their decay products. MACS values at 30 keV extracted from the experimental spectrum-averaged cross sections are obtained and will be discussed. The Kr region, at the border between the so-called weak and strong s-process was also investigated. Atom Trap Trace Analysis (ATTA) was used for the first time for the measurement of a nuclear reaction cross section. After activation in the quasi-Maxwellian neutron flux at SARAF-LiLiT, isotopic ratios were determined for 81Kr(230 ky)/80Kr and 85gKr(10.8 y)/84Kr. The latter ratio was confirmed both by low-level β counting and γ spectrometry. The shorter-lived capture products 79,85m,87Kr were detected by γ -spectrometry and the corresponding neutron-capture MACS of the respective target nuclei 78,84,86Kr were determined. The MACS of the 80Kr(n, γ)81Kr and 84Kr(n, γ)85gKr reactions are still under study. The partial MACS leading to 85mKr(4.5 h) measured in this experiment has interesting implications since this state decays preferentially by γ decay (79%) to 85Rb on a faster time scale than does 85gKr and behaves thus as an s-process branching point.

Measurement of (n,γ) reaction cross section of 186W-isotope at neutron energy of 20.02±0.58 MeV

The cross-section of 186W(n,γ)187W reaction has been measured at an average neutron energy of 20.02±0.58 MeV by using activation technique. The 27Al(n,α)24Na and 115In(n,n´)115mIn reactions have been used for absolute neutron flux measurement. Theoretically the reaction cross-sections have been calculated by using the TALYS-1.9 code. The results from the present work and the EXFOR based literature data have been compared with the evaluated data and calculated data from TALYS-1.9 code.