2n Reaction Research Articles

Production of 16N and obtaining of its gamma spectrum in order to calibrate detectors or determination of fluorine in geological specimens

In this paper, we show a procedure for producing 16N and a method to obtain its gamma spectrum with a NaI(Tl) detector. We also demonstrate the interest of this radioactive element for the purpose of NaI(Tl) detector calibration and for the determination of fluorine in geological specimens using an Alpha Beryllium neutron source. This work consists of a theoretical study which analyzes the characteristics of 16N and nuclear reactions that originate from an Americium Beryllium source of 1Ci activity. We justify our choice of reaction 19F(n,α) 16N and the use of fluorspar as a source of fluorine. The mathematical procedure followed to obtain the gamma rays spectrum produced by 16N in a NaI(Tl) detector is shown.

Determination of the 12C(p, γ)13N reaction rates from the 12C(7Li,6He)13N reaction

The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm−1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S(E) factors and reaction rates for the 12C(p, γ)13N direct capture reaction at energies of astrophysical relevance.

Computer Simulation and Depth Profiling of Light Nuclei by Nuclear Techniques

This article involves computer simulation and surface analysis by nuclear techniques, which are non-destructive. The “energy method of analysis” for nuclear reactions and elastic scattering is used. Energy spectra are computer simulated and compared with experimental data, giving target composition and concentration profile information. The method is successfully applied to depth profiling of 18O and 12C nuclei in thick targets through the 18O(p,α0)15N and 12C(d,p0)13C reactions, respectively. Similarly, elastic scattering of (4He)+ ions is applied to determination of concentration profiles of O and Al for a thick target containing a thin film of aluminium oxide.

Investigation of Some Structural Fusion Materials for (n, 2n) Reactions up to 40 MeV

The knowledge of (n, 2n) cross section is very important and necessary in the reactor technology since a significant portion of the fission neutron spectrum lies above the threshold of (n, 2n) reaction for the most of the reactor materials. The (n, 2n) cross section is neutron multiplier reaction in fusion reactor design. Therefore, (n, 2n) reactions of the selected blanket materials can play a key role for multiplying neutrons in reactor environment. In this study, for some structural fusion materials (n, 2n) reactions such as 27Al(n, 2n)26Al, 51V(n, 2n)50V, 52Cr(n, 2n)51Cr, 55Mn(n, 2n)54Mn, 56Fe(n, 2n)55Fe and 58Ni (n, 2n)57Ni have been carried out up to 40 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. Also in the present work, the (n, 2n) reaction cross-sections have calculated by using evaluated empirical formulas developed by Tel et al. at 14–15 MeV energy. The calculated results are discussed and compared with the experimental data taken from EXFOR database.

Neutron production in ultraintense laser interactions with carbon-deuterated plasma at intensities of 1018 W cm−2

Wide-range neutron energy spectra that are produced when an ultraintense laser with an intensity of 3 × 1018 W cm−2 is focused on a CD2 target have been studied. The experimentally observed spectra and numerically calculated ones, by a three-dimensional Monte Carlo code, indicate that the energy range of the emitted neutrons is larger than that of the D(d,n)3He reaction. The reactions that can participate in neutron production and their relative importance have been analysed. An explanation for the measured spectra is introduced by taking into account the 12C(d,n)13N and D(12c,n)13N reactions. These reactions strongly participate in neutron production due to their high cross sections. Moreover, the neutrons from these reactions will overlap the neutrons from the D(d,n)3He reaction, including the 2.45 MeV neutrons, with increasing energy of the accelerated ions under higher irradiances.

DWBA momentum distribution and its effect on THM

The 18O(p, α) 15N reaction is of primary importance to pin down the uncertainties affecting present-day models of asymptotic giant branch stars. An indirect measurement of the low-energy region of the 18O(p, α) 15N reaction has been performed by means of the Trojan Horse Method. We discuss why the plane wave approximation is justified by evaluating what changes the more correct DWBA approach introduces.

2H( 6He, 7Li)n, 12C( 7Li, 6He) 13N reactions and 12C(p, γ) 13N astrophysical S(E) factors

Angular distributions of 2H( 6He, 7Li) n and 12C( 7Li, 6He) 13N reactions were measured at the HI-13 tandem accelerator, Beijing. Asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be 1.64 ± 0.11 fm − 1 / 2 through distorted wave Born approximation (DWBA) analysis, which was then used to deduce the astrophysical S(E) factors for direct capture in 12C( p, γ) 13N at energies of astrophysical relevance.

Development of a low-level setup for gamma spectroscopy: Application for nuclear astrophysics using reverse kinematics

Abstract It is more and more necessary to improve the sensitivity of gamma-ray spectroscopy systems, especially in nuclear astrophysics. In the case of radiative proton capture reactions, one means is to avoid the reactions on the target impurities by using reverse kinematics. This technique is possible with the LARN accelerator and can provide very clean cross-section measurements. For that purpose, a hydrogen standard has been carried out by means of ion implantation in silicon. In addition, a low-level setup has been put in place on a new beam line of the accelerator. A high efficiency and high resolution germanium detector is used conjointly with a double shielding. A passive lead castle shielding system is used to reduce the natural radioactivity and an active shielding consisting of an anti-cosmic veto is provided by an anticoincidence between the plastic scintillator and the gamma-ray detector. The setup allows a reduction of 70% of the background interference and provides an approximately 200 fold sensitivity gain of between 600 and 3000 keV. Some other developments have also been carried out to optimize the setup. The entire setup and the reverse kinematics have been validated by measuring the cross-section of the 13C(p,γ)14N and 15N(p,γ)16O reactions that present some astrophysical interest.

A study of nuclear transmutation of Th and natU with neutrons produced in a Pb target and U blanket irradiated by 1.6 GeV deuterons

The spallation lead target in the “Energy plus Transmutation” set-up, covered with uranium blanket, was irradiated by the 1.6GeV deuteron beam from the Nuclotron accelerator at the Joint Institute for Nuclear Research in Dubna. The neutrons generated in the subcritical uranium blanket are used to activate the radioactive uranium and thorium samples outside the blanket. Rates of the (n,\( \gamma\)) , (n, f) and (n, 2n) reactions are determined for some residual nuclei. The ratio of the reaction rates R(n, 2n)/R(n, f) is estimated to be 27(9)%. Contributions of the neutrons with energy En > 20 MeV to the (n, f) reaction rate is ∼ 57% for 232Th and ∼ 37% for natU , respectively. To compare with the experimental results, the reaction rates are simulated by generating the neutron fluxes employing two different models, the beam shapes by the MCNPX 2.6.c code and making use of the appropriate libraries of cross-sections. The transmutation power of the set-up is estimated using the average (n,\( \gamma\)) and (n, 2n) reaction rates and compared with some of the results of the TARC experiment.

S-factor measurement of the 13C(p,γ)14N reaction in reverse kinematics

We measure the S-factor of the 13C(p,γ)14N reaction in reverse kinematics for energies ranging from 561 down to 225 keV with a low background experimental setup. The results are compared with previous measurements and an R-matrix treatment is applied to the data in order to obtain the properties of the 511 keV resonance that dominates the cross section at low energies.

Monte-Carlo calculations for neutron yield from photonuclear reactions following bremsstrahlung in tungsten target

The photonuclear reactions of (γ, xn) or (γ, xnp) types can be used to produce high-intensity neutron sources for research and applied purposes. In this work a Monte-Carlo calculation has been used to evaluate the production yields of neutrons from the (γ, n) and (γ, 2n) reactions following the bremsstrahlung produced by 100 and 200 MeV electron beams on the tungsten target. Our calculations indicated that the neutron yield is an increasing function of the target thickness in a considered range from 1.5 to 2.5 mm.

First measurement of the 18O(p,α)15N cross section at astrophysical energies

The 18O(p,α)15N reaction rate has been deduced by means of the Trojan horse method. For the first time the contribution of the 20 keV resonance has been directly evaluated, giving a value about 35% larger than the one in the literature. Moreover, the present approach has allowed to improve the accuracy by a factor 8.5, as it is based on the measured strength instead of spectroscopic measurements. The contribution of the 90 keV resonance has been also determined, which turned out to be of negligible importance to astrophysics.

Asymptotic normalization coefficient and important astrophysical process 15N(p,γ)160

In this work we report the application of the ANC method for the determination of the non-resonant radiative capture amplitude for the important astrophysical CNO cycle reaction 15N(p, γ) 16O, which provides a leak from the CN cycle into the CNO bi-cycle and CNO tri-cycle. It is contributed by the resonance capture to the ground state through two strong 1− resonances and non-resonant capture to the ground state, which interferes with the resonant capture terms. To determine more accurately the contribution from the non-resonant capture we determined the proton ANCs for the ground and seven excited states of 16O by measuring the angular distributions of the peripheral 15N(3He, d)16O proton transfer reaction. Using these ANCs and proton and α resonance widths determined from an R-matrix fit to the data from the 15N(p, α)12C reaction, we calculated the astrophysical S factor for the 15N(p, γ)16O reaction. The results indicate that the direct capture contribution was previously overestimated. We find the astrophysical factor to be S(0) = 36.0 ± 6.0 keVb, which is about a factor of two lower than the presently accepted value. We conclude that for every 2200 ± 300 cycles of the main CN cycle one CN catalyst is lost due to this reaction.

A NOVEL APPROACH TO MEASURE THE CROSS SECTION OF THE18O(p, α)15N RESONANT REACTION IN THE 0-200 keV ENERGY RANGE

The 18O(p, ?)15N reaction is of primary importance to pin down the uncertainties, due to nuclear physics input, affecting present-day models of asymptotic giant branch stars. Its reaction rate can modify both fluorine nucleosynthesis inside such stars and oxygen and nitrogen isotopic ratios, which allow one to constrain the proposed astrophysical scenarios. Thus, an indirect measurement of the low-energy region of the 18O(p, ?)15N reaction has been performed to access, for the first time, the range of relevance for astrophysical application. In particular, a full, high-accuracy spectroscopic study of the 20 and 90 keV resonances has been performed and the strengths deduced to evaluate the reaction rate and the consequences for astrophysics.

Neutron Yield from (γ, n) and (γ, 2n) Reactions following 100 MeV Bremsstrahlung in a Tungsten Target

The photonuclear reactions of (γ, xn) or (γ, xnp) types can be used to produce high-intensity neutron sources for research and applied purposes. In this work a Monte-Carlo calculation has been used to evaluate the production yield of neutrons from the (γ, n) and (γ, 2n) reactions following the bremsstrahlung produced by a 100 MeV electron beam on a tungsten target.

Empirical relation and establishment of shell effects in (n, 2n) reaction cross-sections at 14 MeV

The experimental data for (n, 2n) reaction cross-sections around 14 MeV neutron energy have been collected from the literature and analysed for the isotopes having 1 ≤ Z ≤ 82. The empirical relations for the reaction cross-sections have been obtained, which show fairly good fits with the experimental values. The shell effects have been established at magic nucleon numbers for (n, 2n) reaction cross-sections around 14 MeV neutron energy. The odd-even effects have also been observed as the cross-sections for odd-mass nuclei are higher than their neighbouring even-even nuclei.

New High-Precision Measurement of the Reaction Rate of the 18O(p, α)15N Reaction via THM

AbstractThe 18O(p, α)15N reaction rate has been extracted by means of the Trojan-Horse method. For the first time the contribution of the 20-keV peak has been directly evaluated, giving a value about 35% larger than previously estimated. The present approach has allowed to improve the accuracy of a factor 8.5, as it is based on the measured strength instead of educated guesses or spectroscopic measurements. The contribution of the 90-keV resonance has been determined as well, which turned out to be of negligible importance to astrophysics.

Measurement of the 20 and 90 keV Resonances in theO18(p,α)N15Reaction via the Trojan Horse Method

The 18O(p,alpha)15N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the 18O(p,alpha)15N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated.

Angle-correlated spectrum measurement for two neutrons emitted from (n, 2n) reaction with the coincidence detection technique using a pencil-beam DT neutron source

A technique was developed to measure the angle-correlated neutron energy spectrum with the coincidence detection technique using a pencil-beam DT neutron source at the Fusion Neutronics Source (FNS) of the Japan Atomic Energy Agency (JAEA). Triple differential cross-sections of the 55Mn(n, 2n) reaction were measured first, from which the total 55Mn(n, 2n) reaction cross-section was deduced and compared with JENDL-3.3. The agreement was sufficient to prove the validity of the technique. With the present measuring technique, a complete measurement of a medium-heavy or heavy element such as manganese would become possible through several measurements, because the angle dependence of the emitted neutrons from it is normally weak. The technique will be a useful tool for measuring the angle-correlated neutron spectrum of light elements such as beryllium for investigation of their complicated nuclear reaction mechanism.

Experimental study of the 165Ho(d, 2n) and 165Ho(d, p) nuclear reactions up to 20 MeV for production of the therapeutic radioisotopes 165Er and 166gHo

The radioisotope 165Er ( T 1/2 = 10.36 h) is a candidate for Auger-electron therapy. The β −-emitting 166gHo ( T 1/2 = 26.83 h) is now being explored for various therapeutic applications. In the frame of our systematic study of charged particle production routes of therapeutic radionuclides the excitation functions of the 165Ho(d, 2n) 165Er and 165Ho(d, p) 166gHo reactions were measured up to 20 MeV by using a stacked foil irradiation technique and X/γ-ray spectroscopy. The excitation function of the 165Ho(d, 2n) 165Er reaction was measured for the first time while for the 165Ho(d, p) 166gHo reaction only a single dataset of earlier measured cross-sections was found. The measured excitation functions were compared to the results of different nuclear reaction model codes. The calculated thick target yield of the 165Ho(d, 2n) reaction is significantly higher over the optimal energy range than that for the 165Ho(p, n) reaction investigated earlier by us. The integral yield of the 165Ho(d, p) 166gHo reaction is rather low compared to the established 165Ho(n, γ) 166Ho reaction in a nuclear reactor.